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* powerpc: use swap() to make code cleanerYang Guang2021-12-201-4/+2
| | | | | | | | | | | | Use the macro 'swap()' defined in 'include/linux/minmax.h' to avoid opencoding it. Reported-by: Zeal Robot <zealci@zte.com.cn> Signed-off-by: David Yang <davidcomponentone@gmail.com> Signed-off-by: Yang Guang <yang.guang5@zte.com.cn> [mpe: Add include of linux/minmax.h] Signed-off-by: Michael Ellerman <mpe@ellerman.id.au> Link: https://lore.kernel.org/r/71a702c2189b16c152affd8a8cda1d84ce32741c.1639792543.git.yang.guang5@zte.com.cn
* powerpc/mpic: Use bitmap_zalloc() when applicableChristophe JAILLET2021-12-201-2/+1
| | | | | | | | | | 'mpic->protected' is a bitmap. So use 'bitmap_zalloc()' to simplify code and improve the semantic, instead of hand writing it. Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr> Signed-off-by: Michael Ellerman <mpe@ellerman.id.au> Link: https://lore.kernel.org/r/aa145f674e08044c98f13f1a985faa9cc29c3708.1639777976.git.christophe.jaillet@wanadoo.fr
* selftests/powerpc: skip tests for unavailable mitigations.Sachin Sant2021-12-161-1/+4
| | | | | | | | | | | | | | | | | | | | | | | Mitigation patching test iterates over a set of mitigations irrespective of whether a certain mitigation is supported/available in the kernel. This causes following messages on a kernel where some mitigations are unavailable: Spawned threads enabling/disabling mitigations ... cat: entry_flush: No such file or directory cat: uaccess_flush: No such file or directory Waiting for timeout ... OK This patch adds a check for available mitigations in the kernel. Reported-by: Nageswara R Sastry <rnsastry@linux.ibm.com> Signed-off-by: Sachin Sant <sachinp@linux.vnet.ibm.com> Tested-by: Nageswara R Sastry <rnsastry@linux.ibm.com> Reviewed-by: Russell Currey <ruscur@russell.cc> Signed-off-by: Michael Ellerman <mpe@ellerman.id.au> Link: https://lore.kernel.org/r/163941374362.36967.18016981579099073379.sendpatchset@1.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.ip6.arpa
* powerpc/pseries: use slab context cpumask allocation in CPU hotplug initNicholas Piggin2021-12-161-4/+5
| | | | | | | | | | | | | Slab is up at this point, using the bootmem allocator triggers a warning. Switch to using the regular cpumask allocator. Signed-off-by: Nicholas Piggin <npiggin@gmail.com> Tested-by: Sachin Sant <sachinp@linux.vnet.ibm.com> Reviewed-by: Nathan Lynch <nathanl@linux.ibm.com> Reviewed-by: Laurent Dufour <ldufour@linux.ibm.com> Signed-off-by: Michael Ellerman <mpe@ellerman.id.au> Link: https://lore.kernel.org/r/20211105132923.1582514-1-npiggin@gmail.com
* powerpc/64s/interrupt: avoid saving CFAR in some asynchronous interruptsNicholas Piggin2021-12-161-0/+63
| | | | | | | | | | | | | | | | Reading the CFAR register is quite costly (~20 cycles on POWER9). It is a good idea to have for most synchronous interrupts, but for async ones it is much less important. Doorbell, external, and decrementer interrupts are the important asynchronous ones. HV interrupts can't skip CFAR if KVM HV is possible, because it might be a guest exit that requires CFAR preserved. But the important pseries interrupts can avoid loading CFAR. Signed-off-by: Nicholas Piggin <npiggin@gmail.com> Signed-off-by: Michael Ellerman <mpe@ellerman.id.au> Link: https://lore.kernel.org/r/20210922145452.352571-7-npiggin@gmail.com
* powerpc/64/interrupt: reduce expensive debug testsNicholas Piggin2021-12-161-4/+10
| | | | | | | | | | Move the assertions requiring restart table searches under CONFIG_PPC_IRQ_SOFT_MASK_DEBUG. Signed-off-by: Nicholas Piggin <npiggin@gmail.com> Signed-off-by: Michael Ellerman <mpe@ellerman.id.au> Link: https://lore.kernel.org/r/20210922145452.352571-6-npiggin@gmail.com
* powerpc/64s/interrupt: Don't enable MSR[EE] in irq handlers unless perf is ↵Nicholas Piggin2021-12-164-27/+67
| | | | | | | | | | | | | | | | | | | | | | | | | | | in use Enabling MSR[EE] in interrupt handlers while interrupts are still soft masked allows PMIs to profile interrupt handlers to some degree, beyond what SIAR latching allows. When perf is not being used, this is almost useless work. It requires an extra mtmsrd in the irq handler, and it also opens the door to masked interrupts hitting and requiring replay, which is more expensive than just taking them directly. This effect can be noticable in high IRQ workloads. Avoid enabling MSR[EE] unless perf is currently in use. This saves about 60 cycles (or 8%) on a simple decrementer interrupt microbenchmark. Replayed interrupts drop from 1.4% of all interrupts taken, to 0.003%. This does prevent the soft-nmi interrupt being taken in these handlers, but that's not too reliable anyway. The SMP watchdog will continue to be the reliable way to catch lockups. Signed-off-by: Nicholas Piggin <npiggin@gmail.com> Signed-off-by: Michael Ellerman <mpe@ellerman.id.au> Link: https://lore.kernel.org/r/20210922145452.352571-5-npiggin@gmail.com
* powerpc/64s/perf: add power_pmu_wants_prompt_pmi to say whether perf wants ↵Nicholas Piggin2021-12-162-0/+33
| | | | | | | | | | | | | | | | | PMIs to be soft-NMI Interrupt code enables MSR[EE] in some irq handlers while keeping local irqs disabled via soft-mask, allowing PMI interrupts to be taken as soft-NMI to improve profiling of irq handlers. When perf is not enabled, there is no point to doing this, it's additional overhead. So provide a function that can say if PMIs should be taken promptly if possible. Signed-off-by: Nicholas Piggin <npiggin@gmail.com> Signed-off-by: Michael Ellerman <mpe@ellerman.id.au> Link: https://lore.kernel.org/r/20210922145452.352571-4-npiggin@gmail.com
* powerpc/64s/interrupt: handle MSR EE and RI in interrupt entry wrapperNicholas Piggin2021-12-164-38/+42
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | The mtmsrd to enable MSR[RI] can be combined with the mtmsrd to enable MSR[EE] in interrupt entry code, for those interrupts which enable EE. This helps performance of important synchronous interrupts (e.g., page faults). This is similar to what commit dd152f70bdc1 ("powerpc/64s: system call avoid setting MSR[RI] until we set MSR[EE]") does for system calls. Do this by enabling EE and RI together at the beginning of the entry wrapper if PACA_IRQ_HARD_DIS is clear, and only enabling RI if it is set. Asynchronous interrupts set PACA_IRQ_HARD_DIS, but synchronous ones leave it unchanged, so by default they always get EE=1 unless they have interrupted a caller that is hard disabled. When the sync interrupt later calls interrupt_cond_local_irq_enable(), it will not require another mtmsrd because MSR[EE] was already enabled here. This avoids one mtmsrd L=1 for synchronous interrupts on 64s, which saves about 20 cycles on POWER9. And for kernel-mode interrupts, both synchronous and asynchronous, this saves an additional 40 cycles due to the mtmsrd being moved ahead of mfspr SPRN_AMR, which prevents a SPR scoreboard stall. Signed-off-by: Nicholas Piggin <npiggin@gmail.com> Signed-off-by: Michael Ellerman <mpe@ellerman.id.au> Link: https://lore.kernel.org/r/20210922145452.352571-3-npiggin@gmail.com
* powerpc/64/interrupt: make normal synchronous interrupts enable MSR[EE] if ↵Nicholas Piggin2021-12-161-1/+18
| | | | | | | | | | | | | | | | | | | | | | | | | | possible Make synchronous interrupt handler entry wrappers enable MSR[EE] if MSR[EE] was enabled in the interrupted context. IRQs are soft-disabled at this point so there is no change to high level code, but it's a masked interrupt could fire. This is a performance disadvantage for interrupts which do not later call interrupt_cond_local_irq_enable(), because an an additional mtmsrd or wrtee instruction is executed. However the important synchronous interrupts (e.g., page fault) do enable interrupts, so the performance disadvantage is mostly avoided. In the next patch, MSR[RI] enabling can be combined with MSR[EE] enabling, which mitigates the performance drop for the former and gives a performance advanage for the latter interrupts, on 64s machines. 64e is coming along for the ride for now to avoid divergences with 64s in this tricky code. Signed-off-by: Nicholas Piggin <npiggin@gmail.com> Signed-off-by: Michael Ellerman <mpe@ellerman.id.au> Link: https://lore.kernel.org/r/20210922145452.352571-2-npiggin@gmail.com
* powerpc/pseries/vas: Don't print an error when VAS is unavailableNicholas Piggin2021-12-161-2/+9
| | | | | | | | | | | | | KVM does not support VAS so guests always print a useless error on boot vas: HCALL(398) error -2, query_type 0, result buffer 0x57f2000 Change this to only print the message if the error is not H_FUNCTION. Signed-off-by: Nicholas Piggin <npiggin@gmail.com> Signed-off-by: Michael Ellerman <mpe@ellerman.id.au> Link: https://lore.kernel.org/r/20211126052133.1664375-1-npiggin@gmail.com
* powerpc/perf: Add data source encodings for power10 platformKajol Jain2021-12-161-12/+42
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | The code represent memory/cache level data based on PERF_MEM_LVL_* namespace, which is in the process of deprication in the favour of newer composite PERF_MEM_{LVLNUM_,REMOTE_,SNOOPX_,HOPS_} fields. Add data source encodings to represent cache/memory data based on newer composite PERF_MEM_{LVLNUM_,REMOTE_,SNOOPX_,HOPS_} fields. Add data source encodings to represent data coming from local memory/Remote memory/distant memory and remote/distant cache hits. In order to represent data coming from OpenCAPI cache/memory, we use LVLNUM "PMEM" field which is used to present persistent memory accesses. Result in power10 system with patch changes: localhost:# ./perf mem report --sort="mem,sym,dso" --stdio # Overhead Samples Memory access Symbol Shared Object # ........ ............ ........................ .......................... ................ # 29.46% 2331 L1 or L1 hit [.] __random libc-2.28.so 23.11% 2121 L1 or L1 hit [.] producer_populate_cache producer_consumer 18.56% 1758 L1 or L1 hit [.] __random_r libc-2.28.so 15.64% 1559 L2 or L2 hit [.] __random libc-2.28.so ..... 0.09% 5 Remote socket, same board Any cache hit [.] __random libc-2.28.so 0.07% 4 Remote socket, same board Any cache hit [.] __random libc-2.28.so ..... Signed-off-by: Kajol Jain <kjain@linux.ibm.com> Reviewed-by: Madhavan Srinivasan <maddy@linux.ibm.com> Signed-off-by: Michael Ellerman <mpe@ellerman.id.au> Link: https://lore.kernel.org/r/20211206091749.87585-5-kjain@linux.ibm.com
* powerpc/perf: Add encodings to represent data based on newer composite ↵Kajol Jain2021-12-161-3/+3
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | PERF_MEM_LVLNUM* fields The code represent data coming from L1/L2/L3 cache hits based on PERF_MEM_LVL_* namespace, which is in the process of deprecation in the favour of newer composite PERF_MEM_{LVLNUM_,REMOTE_,SNOOPX_,HOPS_} fields. Add data source encodings to represent L1/L2/L3 cache hits based on newer composite PERF_MEM_{LVLNUM_,REMOTE_,SNOOPX_,HOPS_} fields for power10 and older platforms Result in power9 system without patch changes: localhost:# ./perf mem report --sort="mem,sym,dso" --stdio # Overhead Samples Memory access Symbol Shared Object # ........ ............ ........................ ................................. ................ # 29.51% 1 L2 hit [k] perf_event_exec [kernel.vmlinux] 27.05% 1 L1 hit [k] perf_ctx_unlock [kernel.vmlinux] 13.93% 1 L1 hit [k] vtime_delta [kernel.vmlinux] 13.11% 1 L1 hit [k] prepend_path.isra.11 [kernel.vmlinux] 8.20% 1 L1 hit [.] 00000038.plt_call.__GI_strlen libc-2.28.so 8.20% 1 L1 hit [k] perf_event_interrupt [kernel.vmlinux] Result in power9 system with patch changes: localhost:# ./perf mem report --sort="mem,sym,dso" --stdio # Overhead Samples Memory access Symbol Shared Object # ........ ............ ........................ .......................... ................ # 36.63% 1 L2 or L2 hit [k] perf_event_exec [kernel.vmlinux] 25.50% 1 L1 or L1 hit [k] vtime_delta [kernel.vmlinux] 13.12% 1 L1 or L1 hit [k] unmap_region [kernel.vmlinux] 12.62% 1 L1 or L1 hit [k] perf_sample_event_took [kernel.vmlinux] 6.93% 1 L1 or L1 hit [k] perf_ctx_unlock [kernel.vmlinux] 5.20% 1 L1 or L1 hit [.] __memcpy_power7 libc-2.28.so Signed-off-by: Kajol Jain <kjain@linux.ibm.com> Reviewed-by: Madhavan Srinivasan <maddy@linux.ibm.com> Signed-off-by: Michael Ellerman <mpe@ellerman.id.au> Link: https://lore.kernel.org/r/20211206091749.87585-4-kjain@linux.ibm.com
* perf: Add new macros for mem_hops fieldKajol Jain2021-12-161-1/+4
| | | | | | | | | | | | | | | | | | | | | | | | Add new macros for mem_hops field which can be used to represent remote-node, socket and board level details. Currently the code had macro for HOPS_0, which corresponds to data coming from another core but same node. Add new macros for HOPS_1 to HOPS_3 to represent remote-node, socket and board level data. For ex: Encodings for mem_hops fields with L2 cache: L2 - local L2 L2 | REMOTE | HOPS_0 - remote core, same node L2 L2 | REMOTE | HOPS_1 - remote node, same socket L2 L2 | REMOTE | HOPS_2 - remote socket, same board L2 L2 | REMOTE | HOPS_3 - remote board L2 Signed-off-by: Kajol Jain <kjain@linux.ibm.com> Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org> Signed-off-by: Michael Ellerman <mpe@ellerman.id.au> Link: https://lore.kernel.org/r/20211206091749.87585-2-kjain@linux.ibm.com
* Merge branch 'topic/ppc-kvm' into nextMichael Ellerman2021-12-153-15/+13
|\ | | | | | | Bring in some more KVM commits from our KVM topic branch.
| * KVM: PPC: Book3S HV P9: Use kvm_arch_vcpu_get_wait() to get rcuwait objectSean Christopherson2021-12-141-2/+3
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Use kvm_arch_vcpu_get_wait() to get a vCPU's rcuwait object instead of using vcpu->wait directly in kvmhv_run_single_vcpu(). Functionally, this is a nop as vcpu->arch.waitp is guaranteed to point at vcpu->wait. But that is not obvious at first glance, and a future change coming in via the KVM tree, commit 510958e99721 ("KVM: Force PPC to define its own rcuwait object"), will hide vcpu->wait from architectures that define __KVM_HAVE_ARCH_WQP to prevent generic KVM from attepting to wake a vCPU with the wrong rcuwait object. Reported-by: Sachin Sant <sachinp@linux.vnet.ibm.com> Signed-off-by: Sean Christopherson <seanjc@google.com> Tested-by: Sachin Sant <sachinp@linux.vnet.ibm.com> Signed-off-by: Michael Ellerman <mpe@ellerman.id.au> Link: https://lore.kernel.org/r/20211213174556.3871157-1-seanjc@google.com
| * KVM: PPC: Book3S: Suppress failed alloc warning in H_COPY_TOFROM_GUESTAlexey Kardashevskiy2021-12-021-1/+1
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | H_COPY_TOFROM_GUEST is an hcall for an upper level VM to access its nested VMs memory. The userspace can trigger WARN_ON_ONCE(!(gfp & __GFP_NOWARN)) in __alloc_pages() by constructing a tiny VM which only does H_COPY_TOFROM_GUEST with a too big GPR9 (number of bytes to copy). This silences the warning by adding __GFP_NOWARN. Spotted by syzkaller. Signed-off-by: Alexey Kardashevskiy <aik@ozlabs.ru> Reviewed-by: Fabiano Rosas <farosas@linux.ibm.com> Signed-off-by: Michael Ellerman <mpe@ellerman.id.au> Link: https://lore.kernel.org/r/20210901084550.1658699-1-aik@ozlabs.ru
| * KVM: PPC: Book3S: Suppress warnings when allocating too big memory slotsAlexey Kardashevskiy2021-12-021-2/+6
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | The userspace can trigger "vmalloc size %lu allocation failure: exceeds total pages" via the KVM_SET_USER_MEMORY_REGION ioctl. This silences the warning by checking the limit before calling vzalloc() and returns ENOMEM if failed. This does not call underlying valloc helpers as __vmalloc_node() is only exported when CONFIG_TEST_VMALLOC_MODULE and __vmalloc_node_range() is not exported at all. Spotted by syzkaller. Signed-off-by: Alexey Kardashevskiy <aik@ozlabs.ru> [mpe: Use 'size' for the variable rather than 'cb'] Signed-off-by: Michael Ellerman <mpe@ellerman.id.au> Link: https://lore.kernel.org/r/20210901084512.1658628-1-aik@ozlabs.ru
| * KVM: PPC: Book3S HV P9: Remove unused ri_set local variableNicholas Piggin2021-12-021-10/+3
| | | | | | | | | | | | | | | | | | ri_set is set and never used. Signed-off-by: Nicholas Piggin <npiggin@gmail.com> Signed-off-by: Michael Ellerman <mpe@ellerman.id.au> Link: https://lore.kernel.org/r/20211201052112.2137167-1-npiggin@gmail.com
* | powerpc/powermac: Add additional missing lockdep_register_key()Christophe Leroy2021-12-091-0/+2
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Commit df1f679d19ed ("powerpc/powermac: Add missing lockdep_register_key()") fixed a problem that was causing a WARNING. There are two other places in the same file with the same problem originating from commit 9e607f72748d ("i2c_powermac: shut up lockdep warning"). Add missing lockdep_register_key() Fixes: 9e607f72748d ("i2c_powermac: shut up lockdep warning") Reported-by: Erhard Furtner <erhard_f@mailbox.org> Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu> Depends-on: df1f679d19ed ("powerpc/powermac: Add missing lockdep_register_key()") Signed-off-by: Michael Ellerman <mpe@ellerman.id.au> Link: https://bugzilla.kernel.org/show_bug.cgi?id=200055 Link: https://lore.kernel.org/r/2c7e421874e21b2fb87813d768cf662f630c2ad4.1638984999.git.christophe.leroy@csgroup.eu
* | powerpc/fadump: Fix inaccurate CPU state info in vmcore generated with panicHari Bathini2021-12-092-0/+18
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | In panic path, fadump is triggered via a panic notifier function. Before calling panic notifier functions, smp_send_stop() gets called, which stops all CPUs except the panic'ing CPU. Commit 8389b37dffdc ("powerpc: stop_this_cpu: remove the cpu from the online map.") and again commit bab26238bbd4 ("powerpc: Offline CPU in stop_this_cpu()") started marking CPUs as offline while stopping them. So, if a kernel has either of the above commits, vmcore captured with fadump via panic path would not process register data for all CPUs except the panic'ing CPU. Sample output of crash-utility with such vmcore: # crash vmlinux vmcore ... KERNEL: vmlinux DUMPFILE: vmcore [PARTIAL DUMP] CPUS: 1 DATE: Wed Nov 10 09:56:34 EST 2021 UPTIME: 00:00:42 LOAD AVERAGE: 2.27, 0.69, 0.24 TASKS: 183 NODENAME: XXXXXXXXX RELEASE: 5.15.0+ VERSION: #974 SMP Wed Nov 10 04:18:19 CST 2021 MACHINE: ppc64le (2500 Mhz) MEMORY: 8 GB PANIC: "Kernel panic - not syncing: sysrq triggered crash" PID: 3394 COMMAND: "bash" TASK: c0000000150a5f80 [THREAD_INFO: c0000000150a5f80] CPU: 1 STATE: TASK_RUNNING (PANIC) crash> p -x __cpu_online_mask __cpu_online_mask = $1 = { bits = {0x2, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0} } crash> crash> crash> p -x __cpu_active_mask __cpu_active_mask = $2 = { bits = {0xff, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0} } crash> While this has been the case since fadump was introduced, the issue was not identified for two probable reasons: - In general, the bulk of the vmcores analyzed were from crash due to exception. - The above did change since commit 8341f2f222d7 ("sysrq: Use panic() to force a crash") started using panic() instead of deferencing NULL pointer to force a kernel crash. But then commit de6e5d38417e ("powerpc: smp_send_stop do not offline stopped CPUs") stopped marking CPUs as offline till kernel commit bab26238bbd4 ("powerpc: Offline CPU in stop_this_cpu()") reverted that change. To ensure post processing register data of all other CPUs happens as intended, let panic() function take the crash friendly path (read crash_smp_send_stop()) with the help of crash_kexec_post_notifiers option. Also, as register data for all CPUs is captured by f/w, skip IPI callbacks here for fadump, to avoid any complications in finding the right backtraces. Signed-off-by: Hari Bathini <hbathini@linux.ibm.com> Signed-off-by: Michael Ellerman <mpe@ellerman.id.au> Link: https://lore.kernel.org/r/20211207103719.91117-2-hbathini@linux.ibm.com
* | powerpc: handle kdump appropriately with crash_kexec_post_notifiers optionHari Bathini2021-12-091-0/+30
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Kdump can be triggered after panic_notifers since commit f06e5153f4ae2 ("kernel/panic.c: add "crash_kexec_post_notifiers" option for kdump after panic_notifers") introduced crash_kexec_post_notifiers option. But using this option would mean smp_send_stop(), that marks all other CPUs as offline, gets called before kdump is triggered. As a result, kdump routines fail to save other CPUs' registers. To fix this, kdump friendly crash_smp_send_stop() function was introduced with kernel commit 0ee59413c967 ("x86/panic: replace smp_send_stop() with kdump friendly version in panic path"). Override this kdump friendly weak function to handle crash_kexec_post_notifiers option appropriately on powerpc. Reported-by: kernel test robot <lkp@intel.com> Signed-off-by: Hari Bathini <hbathini@linux.ibm.com> [Fixed signature of crash_stop_this_cpu() - reported by lkp@intel.com] Signed-off-by: Michael Ellerman <mpe@ellerman.id.au> Link: https://lore.kernel.org/r/20211207103719.91117-1-hbathini@linux.ibm.com
* | selftests/powerpc/spectre_v2: Return skip code when miss_percent is highThadeu Lima de Souza Cascardo2021-12-091-1/+1
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | A mis-match between reported and actual mitigation is not restricted to the Vulnerable case. The guest might also report the mitigation as "Software count cache flush" and the host will still mitigate with branch cache disabled. So, instead of skipping depending on the detected mitigation, simply skip whenever the detected miss_percent is the expected one for a fully mitigated system, that is, above 95%. Signed-off-by: Thadeu Lima de Souza Cascardo <cascardo@canonical.com> Signed-off-by: Michael Ellerman <mpe@ellerman.id.au> Link: https://lore.kernel.org/r/20211207130557.40566-1-cascardo@canonical.com
* | powerpc/cell: Fix clang -Wimplicit-fallthrough warningAnders Roxell2021-12-091-0/+1
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Clang warns: arch/powerpc/platforms/cell/pervasive.c:81:2: error: unannotated fall-through between switch labels case SRR1_WAKEEE: ^ arch/powerpc/platforms/cell/pervasive.c:81:2: note: insert 'break;' to avoid fall-through case SRR1_WAKEEE: ^ break; 1 error generated. Clang is more pedantic than GCC, which does not warn when failing through to a case that is just break or return. Clang's version is more in line with the kernel's own stance in deprecated.rst. Add athe missing break to silence the warning. Fixes: 6e83985b0f6e ("powerpc/cbe: Do not process external or decremeter interrupts from sreset") Reported-by: Naresh Kamboju <naresh.kamboju@linaro.org> Signed-off-by: Anders Roxell <anders.roxell@linaro.org> Reviewed-by: Nathan Chancellor <nathan@kernel.org> Reviewed-by: Arnd Bergmann <arnd@arndb.de> Signed-off-by: Michael Ellerman <mpe@ellerman.id.au> Link: https://lore.kernel.org/r/20211207110228.698956-1-anders.roxell@linaro.org
* | macintosh: Add const to of_device_idXiang wangx2021-12-091-1/+1
| | | | | | | | | | | | | | | | | | struct of_device_id should normally be const. Signed-off-by: Xiang wangx <wangxiang@cdjrlc.com> Signed-off-by: Michael Ellerman <mpe@ellerman.id.au> Link: https://lore.kernel.org/r/20211205130925.28389-1-wangxiang@cdjrlc.com
* | powerpc/inst: Optimise copy_inst_from_kernel_nofault()Christophe Leroy2021-12-092-18/+24
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | copy_inst_from_kernel_nofault() uses copy_from_kernel_nofault() to copy one or two 32bits words. This means calling an out-of-line function which itself calls back copy_from_kernel_nofault_allowed() then performs a generic copy with loops. Rewrite copy_inst_from_kernel_nofault() to do everything at a single place and use __get_kernel_nofault() directly to perform single accesses without loops. Allthough the generic function uses pagefault_disable(), it is not required on powerpc because do_page_fault() bails earlier when a kernel mode fault happens on a kernel address. As the function has now become very small, inline it. With this change, on an 8xx the time spent in the loop in ftrace_replace_code() is reduced by 23% at function tracer activation and 27% at nop tracer activation. The overall time to activate function tracer (measured with shell command 'time') is 570ms before the patch and 470ms after the patch. Even vmlinux size is reduced (by 152 instruction). Before the patch: 00000018 <copy_inst_from_kernel_nofault>: 18: 94 21 ff e0 stwu r1,-32(r1) 1c: 7c 08 02 a6 mflr r0 20: 38 a0 00 04 li r5,4 24: 93 e1 00 1c stw r31,28(r1) 28: 7c 7f 1b 78 mr r31,r3 2c: 38 61 00 08 addi r3,r1,8 30: 90 01 00 24 stw r0,36(r1) 34: 48 00 00 01 bl 34 <copy_inst_from_kernel_nofault+0x1c> 34: R_PPC_REL24 copy_from_kernel_nofault 38: 2c 03 00 00 cmpwi r3,0 3c: 40 82 00 0c bne 48 <copy_inst_from_kernel_nofault+0x30> 40: 81 21 00 08 lwz r9,8(r1) 44: 91 3f 00 00 stw r9,0(r31) 48: 80 01 00 24 lwz r0,36(r1) 4c: 83 e1 00 1c lwz r31,28(r1) 50: 38 21 00 20 addi r1,r1,32 54: 7c 08 03 a6 mtlr r0 58: 4e 80 00 20 blr After the patch (before inlining): 00000018 <copy_inst_from_kernel_nofault>: 18: 3d 20 b0 00 lis r9,-20480 1c: 7c 04 48 40 cmplw r4,r9 20: 7c 69 1b 78 mr r9,r3 24: 41 80 00 14 blt 38 <copy_inst_from_kernel_nofault+0x20> 28: 81 44 00 00 lwz r10,0(r4) 2c: 38 60 00 00 li r3,0 30: 91 49 00 00 stw r10,0(r9) 34: 4e 80 00 20 blr 38: 38 60 ff de li r3,-34 3c: 4e 80 00 20 blr 40: 38 60 ff f2 li r3,-14 44: 4e 80 00 20 blr Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu> [mpe: Add clang workaround, with version check as suggested by Nathan] Signed-off-by: Michael Ellerman <mpe@ellerman.id.au> Link: https://lore.kernel.org/r/0d5b12183d5176dd702d29ad94c39c384e51c78f.1638208156.git.christophe.leroy@csgroup.eu
* | powerpc/inst: Move ppc_inst_t definition in asm/reg.hChristophe Leroy2021-12-094-11/+13
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Because of circular inclusion of asm/hw_breakpoint.h, we need to move definition of asm/reg.h outside of inst.h so that asm/hw_breakpoint.h gets it without including asm/inst.h Also remove asm/inst.h from asm/uprobes.h as it's not needed anymore. Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu> Signed-off-by: Michael Ellerman <mpe@ellerman.id.au> Link: https://lore.kernel.org/r/4b79f1491118af96b1ac0735e74aeca02ea4c04e.1638208156.git.christophe.leroy@csgroup.eu
* | powerpc/inst: Define ppc_inst_t as u32 on PPC32Christophe Leroy2021-12-092-8/+15
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Unlike PPC64 ABI, PPC32 uses the stack to pass a parameter defined as a struct, even when the struct has a single simple element. To avoid that, define ppc_inst_t as u32 on PPC32. Keep it as 'struct ppc_inst' when __CHECKER__ is defined so that sparse can perform type checking. Also revert commit 511eea5e2ccd ("powerpc/kprobes: Fix Oops by passing ppc_inst as a pointer to emulate_step() on ppc32") as now the instruction to be emulated is passed as a register to emulate_step(). Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu> Signed-off-by: Michael Ellerman <mpe@ellerman.id.au> Link: https://lore.kernel.org/r/c6d0c46f598f76ad0b0a88bc0d84773bd921b17c.1638208156.git.christophe.leroy@csgroup.eu
* | powerpc/inst: Define ppc_inst_tChristophe Leroy2021-12-0923-112/+112
| | | | | | | | | | | | | | | | | | | | In order to stop using 'struct ppc_inst' on PPC32, define a ppc_inst_t typedef. Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu> Signed-off-by: Michael Ellerman <mpe@ellerman.id.au> Link: https://lore.kernel.org/r/fe5baa2c66fea9db05a8b300b3e8d2880a42596c.1638208156.git.christophe.leroy@csgroup.eu
* | powerpc/inst: Refactor ___get_user_instr()Christophe Leroy2021-12-091-11/+2
| | | | | | | | | | | | | | | | | | | | PPC64 version of ___get_user_instr() can be used for PPC32 as well, by simply disabling the suffix part with IS_ENABLED(CONFIG_PPC64). Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu> Signed-off-by: Michael Ellerman <mpe@ellerman.id.au> Link: https://lore.kernel.org/r/1f0ede830ccb33a659119a55cb590820c27004db.1638208156.git.christophe.leroy@csgroup.eu
* | powerpc/32s: Allocate one 256k IBAT instead of two consecutives 128k IBATsChristophe Leroy2021-12-091-3/+2
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Today we have the following IBATs allocated: ---[ Instruction Block Address Translation ]--- 0: 0xc0000000-0xc03fffff 0x00000000 4M Kernel x m 1: 0xc0400000-0xc05fffff 0x00400000 2M Kernel x m 2: 0xc0600000-0xc06fffff 0x00600000 1M Kernel x m 3: 0xc0700000-0xc077ffff 0x00700000 512K Kernel x m 4: 0xc0780000-0xc079ffff 0x00780000 128K Kernel x m 5: 0xc07a0000-0xc07bffff 0x007a0000 128K Kernel x m 6: - 7: - The two 128K should be a single 256K instead. When _etext is not aligned to 128Kbytes, the system will allocate all necessary BATs to the lower 128Kbytes boundary, then allocate an additional 128Kbytes BAT for the remaining block. Instead, align the top to 128Kbytes so that the function directly allocates a 256Kbytes last block: ---[ Instruction Block Address Translation ]--- 0: 0xc0000000-0xc03fffff 0x00000000 4M Kernel x m 1: 0xc0400000-0xc05fffff 0x00400000 2M Kernel x m 2: 0xc0600000-0xc06fffff 0x00600000 1M Kernel x m 3: 0xc0700000-0xc077ffff 0x00700000 512K Kernel x m 4: 0xc0780000-0xc07bffff 0x00780000 256K Kernel x m 5: - 6: - 7: - Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu> Signed-off-by: Michael Ellerman <mpe@ellerman.id.au> Link: https://lore.kernel.org/r/ab58b296832b0ec650e2203200e060adbcb2677d.1637930421.git.christophe.leroy@csgroup.eu
* | powerpc: Remove CONFIG_PPC_HAVE_KUAP and CONFIG_PPC_HAVE_KUEPChristophe Leroy2021-12-091-21/+0
| | | | | | | | | | | | | | | | | | | | All platforms now have KUAP and KUEP so remove CONFIG_PPC_HAVE_KUAP and CONFIG_PPC_HAVE_KUEP. Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu> Signed-off-by: Michael Ellerman <mpe@ellerman.id.au> Link: https://lore.kernel.org/r/a3c007ad0951965199e6ab2ef1035966bc66e771.1634627931.git.christophe.leroy@csgroup.eu
* | powerpc/kuap: Wire-up KUAP on book3e/64Christophe Leroy2021-12-092-6/+35
| | | | | | | | | | | | | | | | | | | | | | This adds KUAP support to book3e/64. This is done by reading the content of SPRN_MAS1 and checking the TID at the time user pgtable is loaded. Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu> Signed-off-by: Michael Ellerman <mpe@ellerman.id.au> Link: https://lore.kernel.org/r/e2c2c9375afd4bbc06aa904d0103a5f5102a2b1a.1634627931.git.christophe.leroy@csgroup.eu
* | powerpc/kuap: Wire-up KUAP on 85xx in 32 bits mode.Christophe Leroy2021-12-092-0/+13
| | | | | | | | | | | | | | | | | | | | | | This adds KUAP support to 85xx in 32 bits mode. This is done by reading the content of SPRN_MAS1 and checking the TID at the time user pgtable is loaded. Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu> Signed-off-by: Michael Ellerman <mpe@ellerman.id.au> Link: https://lore.kernel.org/r/f8696f8980ca1532ada3a2f0e0a03e756269c7fe.1634627931.git.christophe.leroy@csgroup.eu
* | powerpc/kuap: Wire-up KUAP on 40xChristophe Leroy2021-12-093-2/+15
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | This adds KUAP support to 40x. This is done by checking the content of SPRN_PID at the time user pgtable is loaded. 40x doesn't have KUEP, but KUAP implies KUEP because when the PID doesn't match the page's PID, the page cannot be read nor executed. So KUEP is now automatically selected when KUAP is selected and disabled when KUAP is disabled. Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu> Signed-off-by: Michael Ellerman <mpe@ellerman.id.au> Link: https://lore.kernel.org/r/aaefa91897ddc42ac11019dc0e1d1a525bd08e90.1634627931.git.christophe.leroy@csgroup.eu
* | powerpc/kuap: Wire-up KUAP on 44xChristophe Leroy2021-12-092-0/+17
| | | | | | | | | | | | | | | | | | | | | | This adds KUAP support to 44x. This is done by checking the content of SPRN_PID at the time it is read and written into SPRN_MMUCR. Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu> Signed-off-by: Michael Ellerman <mpe@ellerman.id.au> Link: https://lore.kernel.org/r/7d6c3f1978a26feada74b084f651e8cf1e3b3a47.1634627931.git.christophe.leroy@csgroup.eu
* | powerpc: Add KUAP support for BOOKE and 40xChristophe Leroy2021-12-096-1/+131
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | On booke/40x we don't have segments like book3s/32. On booke/40x we don't have access protection groups like 8xx. Use the PID register to provide user access protection. Kernel address space can be accessed with any PID. User address space has to be accessed with the PID of the user. User PID is always not null. Everytime the kernel is entered, set PID register to 0 and restore PID register when returning to user. Everytime kernel needs to access user data, PID is restored for the access. In TLB miss handlers, check the PID and bail out to data storage exception when PID is 0 and accessed address is in user space. Note that also forbids execution of user text by kernel except when user access is unlocked. But this shouldn't be a problem as the kernel is not supposed to ever run user text. This patch prepares the infrastructure but the real activation of KUAP is done by following patches for each processor type one by one. Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu> Signed-off-by: Michael Ellerman <mpe@ellerman.id.au> Link: https://lore.kernel.org/r/5d65576a8e31e9480415785a180c92dd4e72306d.1634627931.git.christophe.leroy@csgroup.eu
* | powerpc/kuap: Make PPC_KUAP_DEBUG depend on PPC_KUAP onlyChristophe Leroy2021-12-091-1/+1
| | | | | | | | | | | | | | | | | | | | | | | | | | PPC_KUAP_DEBUG is supported by all platforms doing PPC_KUAP, it doesn't depend on Radix on book3s/64. This will avoid adding one more dependency when implementing KUAP on book3e/64. Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu> Signed-off-by: Michael Ellerman <mpe@ellerman.id.au> Link: https://lore.kernel.org/r/a5ff6228a36e51783b83d8c10d058db76e450f63.1634627931.git.christophe.leroy@csgroup.eu
* | powerpc/kuap: Prepare for supporting KUAP on BOOK3E/64Christophe Leroy2021-12-094-5/+14
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Also call kuap_lock() and kuap_save_and_lock() from interrupt functions with CONFIG_PPC64. For book3s/64 we keep them empty as it is done in assembly. Also do the locked assert when switching task unless it is book3s/64. Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu> Signed-off-by: Michael Ellerman <mpe@ellerman.id.au> Link: https://lore.kernel.org/r/1cbf94e26e6d6e2e028fd687588a7e6622d454a6.1634627931.git.christophe.leroy@csgroup.eu
* | powerpc/config: Add CONFIG_BOOKE_OR_40xChristophe Leroy2021-12-0912-16/+21
| | | | | | | | | | | | | | | | | | | | | | | | | | We have many functionnalities common to 40x and BOOKE, it leads to many places with #if defined(CONFIG_BOOKE) || defined(CONFIG_40x). We are going to add a few more with KUAP for booke/40x, so create a new symbol which is defined when either BOOKE or 40x is defined. Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu> Signed-off-by: Michael Ellerman <mpe@ellerman.id.au> Link: https://lore.kernel.org/r/9a3dbd60924cb25c9f944d3d8205ac5a0d15e229.1634627931.git.christophe.leroy@csgroup.eu
* | powerpc/nohash: Move setup_kuap out of 8xx.cChristophe Leroy2021-12-093-22/+32
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | In order to reuse it on booke/4xx, move KUAP setup routine out of 8xx.c Make them usable on SMP by removing the __init tag as it is called for each CPU. And use __prevent_user_access() instead of hard coding initial lock. Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu> Signed-off-by: Michael Ellerman <mpe@ellerman.id.au> Link: https://lore.kernel.org/r/ae35eec3426509efc2b8ae69586c822e2fe2642a.1634627931.git.christophe.leroy@csgroup.eu
* | powerpc/kuap: Add kuap_lock()Christophe Leroy2021-12-095-6/+28
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Add kuap_lock() and call it when entering interrupts from user. It is called kuap_lock() as it is similar to kuap_save_and_lock() without the save. However book3s/32 already have a kuap_lock(). Rename it kuap_lock_addr(). Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu> Signed-off-by: Michael Ellerman <mpe@ellerman.id.au> Link: https://lore.kernel.org/r/4437e2deb9f6f549f7089d45e9c6f96a7e77905a.1634627931.git.christophe.leroy@csgroup.eu
* | powerpc/kuap: Remove __kuap_assert_locked()Christophe Leroy2021-12-094-18/+2
| | | | | | | | | | | | | | | | | | | | | | | | | | __kuap_assert_locked() is redundant with __kuap_get_and_assert_locked(). Move the verification of CONFIG_PPC_KUAP_DEBUG in kuap_assert_locked() and make it call __kuap_get_and_assert_locked() directly. Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu> Signed-off-by: Michael Ellerman <mpe@ellerman.id.au> Link: https://lore.kernel.org/r/1a60198a25d2ba38a37f1b92bc7d096435df4224.1634627931.git.christophe.leroy@csgroup.eu
* | powerpc/kuap: Check KUAP activation in generic functionsChristophe Leroy2021-12-094-76/+56
| | | | | | | | | | | | | | | | | | | | | | | | Today, every platform checks that KUAP is not de-activated before doing the real job. Move the verification out of platform specific functions. Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu> Signed-off-by: Michael Ellerman <mpe@ellerman.id.au> Link: https://lore.kernel.org/r/894f110397fcd248e125fb855d1e863e4e633a0d.1634627931.git.christophe.leroy@csgroup.eu
* | powerpc/kuap: Add a generic intermediate layerChristophe Leroy2021-12-094-37/+86
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Make the following functions generic to all platforms. - bad_kuap_fault() - kuap_assert_locked() - kuap_save_and_lock() (PPC32 only) - kuap_kernel_restore() - kuap_get_and_assert_locked() And for all platforms except book3s/64 - allow_user_access() - prevent_user_access() - prevent_user_access_return() - restore_user_access() Prepend __ in front of the name of platform specific ones. For now the generic just calls the platform specific, but next patch will move redundant parts of specific functions into the generic one. Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu> Signed-off-by: Michael Ellerman <mpe@ellerman.id.au> Link: https://lore.kernel.org/r/eaef143a8dae7288cd34565ffa7b49c16aee1ec3.1634627931.git.christophe.leroy@csgroup.eu
* | powerpc/kuep: Remove 'nosmep' boot time parameter except for book3s/64Christophe Leroy2021-12-097-37/+16
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Deactivating KUEP at boot time is unrelevant for PPC32 and BOOK3E/64. Remove it. It allows to refactor setup_kuep() via a __weak function that only PPC64s will overide for now. Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu> [mpe: Fix CONFIG_PPC_BOOKS_64 -> CONFIG_PPC_BOOK3S_64 typo] Signed-off-by: Michael Ellerman <mpe@ellerman.id.au> Link: https://lore.kernel.org/r/4c36df18b41c988c4512f45d96220486adbe4c99.1634627931.git.christophe.leroy@csgroup.eu
* | powerpc/32s: Save content of sr0 to avoid 'mfsr'Christophe Leroy2021-12-098-14/+33
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Calling 'mfsr' to get the content of segment registers is heavy, in addition it requires clearing of the 'reserved' bits. In order to avoid this operation, save it in mm context and in thread struct. The saved sr0 is the one used by kernel, this means that on locking entry it can be used as is. For unlocking, the only thing to do is to clear SR_NX. This improves null_syscall selftest by 12 cycles, ie 4%. Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu> Signed-off-by: Michael Ellerman <mpe@ellerman.id.au> Link: https://lore.kernel.org/r/b02baf2ed8f09bad910dfaeeb7353b2ae6830525.1634627931.git.christophe.leroy@csgroup.eu
* | powerpc/32s: Do kuep_lock() and kuep_unlock() in assemblyChristophe Leroy2021-12-099-49/+119
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | When interrupt and syscall entries where converted to C, KUEP locking and unlocking was also converted. It improved performance by unrolling the loop, and allowed easily implementing boot time deactivation of KUEP. However, null_syscall selftest shows that KUEP is still heavy (361 cycles with KUEP, 212 cycles without). A way to improve more is to group 'mtsr's together, instead of repeating 'addi' + 'mtsr' several times. In order to do that, more registers need to be available. In C, GCC will always be able to provide the requested number of registers, but at the cost of saving some data on the stack, which is counter performant here. So let's do it in assembly, when we have full control of which register can be used. It also has the advantage of locking earlier and unlocking later and it helps GCC generating less tricky code. The only drawback is to make boot time deactivation less straight forward and require 'hand' instruction patching. Group 'mtsr's by 4. With this change, null_syscall selftest reports 336 cycles. Without the change it was 361 cycles, that's a 7% reduction. Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu> Signed-off-by: Michael Ellerman <mpe@ellerman.id.au> Link: https://lore.kernel.org/r/115cb279e9b9948dfd93a065e047081c59e3a2a6.1634627931.git.christophe.leroy@csgroup.eu
* | powerpc/32s: Remove capability to disable KUEP at boottimeChristophe Leroy2021-12-092-10/+3
| | | | | | | | | | | | | | | | | | | | | | | | Disabling KUEP at boottime makes things unnecessarily complex. Still allow disabling KUEP at build time, but when it's built-in it is always there. Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu> Signed-off-by: Michael Ellerman <mpe@ellerman.id.au> Link: https://lore.kernel.org/r/96f583f82423a29a4205c60b9721079111b35567.1634627931.git.christophe.leroy@csgroup.eu
* | powerpc/book3e: Activate KUEP at all timeChristophe Leroy2021-12-092-0/+3
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | On book3e, - When using 64 bits PTE: User pages don't have the SX bit defined so KUEP is always active. - When using 32 bits PTE: Implement KUEP by clearing SX bit during TLB miss for user pages. The impact is minimal and worth neither boot time nor build time selection. Activate it at all time. Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu> Signed-off-by: Michael Ellerman <mpe@ellerman.id.au> Link: https://lore.kernel.org/r/e376b114283fb94504e2aa2de846780063252cde.1634627931.git.christophe.leroy@csgroup.eu
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