From d39268ad24c0fd0665d0c5cf55a7c1a0ebf94766 Mon Sep 17 00:00:00 2001 From: Dave Hansen Date: Fri, 18 Mar 2022 06:52:59 -0700 Subject: x86/mm/tlb: Revert retpoline avoidance approach 0day reported a regression on a microbenchmark which is intended to stress the TLB flushing path: https://lore.kernel.org/all/20220317090415.GE735@xsang-OptiPlex-9020/ It pointed at a commit from Nadav which intended to remove retpoline overhead in the TLB flushing path by taking the 'cond'-ition in on_each_cpu_cond_mask(), pre-calculating it, and incorporating it into 'cpumask'. That allowed the code to use a bunch of earlier direct calls instead of later indirect calls that need a retpoline. But, in practice, threads can go idle (and into lazy TLB mode where they don't need to flush their TLB) between the early and late calls. It works in this direction and not in the other because TLB-flushing threads tend to hold mmap_lock for write. Contention on that lock causes threads to _go_ idle right in this early/late window. There was not any performance data in the original commit specific to the retpoline overhead. I did a few tests on a system with retpolines: https://lore.kernel.org/all/dd8be93c-ded6-b962-50d4-96b1c3afb2b7@intel.com/ which showed a possible small win. But, that small win pales in comparison with the bigger loss induced on non-retpoline systems. Revert the patch that removed the retpolines. This was not a clean revert, but it was self-contained enough not to be too painful. Fixes: 6035152d8eeb ("x86/mm/tlb: Open-code on_each_cpu_cond_mask() for tlb_is_not_lazy()") Reported-by: kernel test robot Signed-off-by: Dave Hansen Signed-off-by: Borislav Petkov Acked-by: Nadav Amit Cc: Link: https://lkml.kernel.org/r/164874672286.389.7021457716635788197.tip-bot2@tip-bot2 --- arch/x86/mm/tlb.c | 37 +++++-------------------------------- 1 file changed, 5 insertions(+), 32 deletions(-) (limited to 'arch') diff --git a/arch/x86/mm/tlb.c b/arch/x86/mm/tlb.c index 6eb4d91d5365..d400b6d9d246 100644 --- a/arch/x86/mm/tlb.c +++ b/arch/x86/mm/tlb.c @@ -855,13 +855,11 @@ done: nr_invalidate); } -static bool tlb_is_not_lazy(int cpu) +static bool tlb_is_not_lazy(int cpu, void *data) { return !per_cpu(cpu_tlbstate_shared.is_lazy, cpu); } -static DEFINE_PER_CPU(cpumask_t, flush_tlb_mask); - DEFINE_PER_CPU_SHARED_ALIGNED(struct tlb_state_shared, cpu_tlbstate_shared); EXPORT_PER_CPU_SYMBOL(cpu_tlbstate_shared); @@ -890,36 +888,11 @@ STATIC_NOPV void native_flush_tlb_multi(const struct cpumask *cpumask, * up on the new contents of what used to be page tables, while * doing a speculative memory access. */ - if (info->freed_tables) { + if (info->freed_tables) on_each_cpu_mask(cpumask, flush_tlb_func, (void *)info, true); - } else { - /* - * Although we could have used on_each_cpu_cond_mask(), - * open-coding it has performance advantages, as it eliminates - * the need for indirect calls or retpolines. In addition, it - * allows to use a designated cpumask for evaluating the - * condition, instead of allocating one. - * - * This code works under the assumption that there are no nested - * TLB flushes, an assumption that is already made in - * flush_tlb_mm_range(). - * - * cond_cpumask is logically a stack-local variable, but it is - * more efficient to have it off the stack and not to allocate - * it on demand. Preemption is disabled and this code is - * non-reentrant. - */ - struct cpumask *cond_cpumask = this_cpu_ptr(&flush_tlb_mask); - int cpu; - - cpumask_clear(cond_cpumask); - - for_each_cpu(cpu, cpumask) { - if (tlb_is_not_lazy(cpu)) - __cpumask_set_cpu(cpu, cond_cpumask); - } - on_each_cpu_mask(cond_cpumask, flush_tlb_func, (void *)info, true); - } + else + on_each_cpu_cond_mask(tlb_is_not_lazy, flush_tlb_func, + (void *)info, 1, cpumask); } void flush_tlb_multi(const struct cpumask *cpumask, -- cgit v1.2.3 From 9ce02f0fc68326dd1f87a0a3a4c6ae7fdd39e6f6 Mon Sep 17 00:00:00 2001 From: Vincent Mailhol Date: Thu, 24 Mar 2022 11:37:42 +0900 Subject: x86/bug: Prevent shadowing in __WARN_FLAGS The macro __WARN_FLAGS() uses a local variable named "f". This being a common name, there is a risk of shadowing other variables. For example, GCC would yield: | In file included from ./include/linux/bug.h:5, | from ./include/linux/cpumask.h:14, | from ./arch/x86/include/asm/cpumask.h:5, | from ./arch/x86/include/asm/msr.h:11, | from ./arch/x86/include/asm/processor.h:22, | from ./arch/x86/include/asm/timex.h:5, | from ./include/linux/timex.h:65, | from ./include/linux/time32.h:13, | from ./include/linux/time.h:60, | from ./include/linux/stat.h:19, | from ./include/linux/module.h:13, | from virt/lib/irqbypass.mod.c:1: | ./include/linux/rcupdate.h: In function 'rcu_head_after_call_rcu': | ./arch/x86/include/asm/bug.h:80:21: warning: declaration of 'f' shadows a parameter [-Wshadow] | 80 | __auto_type f = BUGFLAG_WARNING|(flags); \ | | ^ | ./include/asm-generic/bug.h:106:17: note: in expansion of macro '__WARN_FLAGS' | 106 | __WARN_FLAGS(BUGFLAG_ONCE | \ | | ^~~~~~~~~~~~ | ./include/linux/rcupdate.h:1007:9: note: in expansion of macro 'WARN_ON_ONCE' | 1007 | WARN_ON_ONCE(func != (rcu_callback_t)~0L); | | ^~~~~~~~~~~~ | In file included from ./include/linux/rbtree.h:24, | from ./include/linux/mm_types.h:11, | from ./include/linux/buildid.h:5, | from ./include/linux/module.h:14, | from virt/lib/irqbypass.mod.c:1: | ./include/linux/rcupdate.h:1001:62: note: shadowed declaration is here | 1001 | rcu_head_after_call_rcu(struct rcu_head *rhp, rcu_callback_t f) | | ~~~~~~~~~~~~~~~^ For reference, sparse also warns about it, c.f. [1]. This patch renames the variable from f to __flags (with two underscore prefixes as suggested in the Linux kernel coding style [2]) in order to prevent collisions. [1] https://lore.kernel.org/all/CAFGhKbyifH1a+nAMCvWM88TK6fpNPdzFtUXPmRGnnQeePV+1sw@mail.gmail.com/ [2] Linux kernel coding style, section 12) Macros, Enums and RTL, paragraph 5) namespace collisions when defining local variables in macros resembling functions https://www.kernel.org/doc/html/latest/process/coding-style.html#macros-enums-and-rtl Fixes: bfb1a7c91fb7 ("x86/bug: Merge annotate_reachable() into_BUG_FLAGS() asm") Signed-off-by: Vincent Mailhol Signed-off-by: Peter Zijlstra (Intel) Reviewed-by: Nick Desaulniers Acked-by: Josh Poimboeuf Link: https://lkml.kernel.org/r/20220324023742.106546-1-mailhol.vincent@wanadoo.fr --- arch/x86/include/asm/bug.h | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) (limited to 'arch') diff --git a/arch/x86/include/asm/bug.h b/arch/x86/include/asm/bug.h index 4d20a293c6fd..aaf0cb0db4ae 100644 --- a/arch/x86/include/asm/bug.h +++ b/arch/x86/include/asm/bug.h @@ -78,9 +78,9 @@ do { \ */ #define __WARN_FLAGS(flags) \ do { \ - __auto_type f = BUGFLAG_WARNING|(flags); \ + __auto_type __flags = BUGFLAG_WARNING|(flags); \ instrumentation_begin(); \ - _BUG_FLAGS(ASM_UD2, f, ASM_REACHABLE); \ + _BUG_FLAGS(ASM_UD2, __flags, ASM_REACHABLE); \ instrumentation_end(); \ } while (0) -- cgit v1.2.3 From be8a096521ca1a252bf078b347f96ce94582612e Mon Sep 17 00:00:00 2001 From: Peter Zijlstra Date: Mon, 28 Mar 2022 13:13:41 +0200 Subject: x86,bpf: Avoid IBT objtool warning Clang can inline emit_indirect_jump() and then folds constants, which results in: | vmlinux.o: warning: objtool: emit_bpf_dispatcher()+0x6a4: relocation to !ENDBR: .text.__x86.indirect_thunk+0x40 | vmlinux.o: warning: objtool: emit_bpf_dispatcher()+0x67d: relocation to !ENDBR: .text.__x86.indirect_thunk+0x40 | vmlinux.o: warning: objtool: emit_bpf_tail_call_indirect()+0x386: relocation to !ENDBR: .text.__x86.indirect_thunk+0x20 | vmlinux.o: warning: objtool: emit_bpf_tail_call_indirect()+0x35d: relocation to !ENDBR: .text.__x86.indirect_thunk+0x20 Suppress the optimization such that it must emit a code reference to the __x86_indirect_thunk_array[] base. Signed-off-by: Peter Zijlstra (Intel) Acked-by: Alexei Starovoitov Link: https://lkml.kernel.org/r/20220405075531.GB30877@worktop.programming.kicks-ass.net --- arch/x86/net/bpf_jit_comp.c | 1 + 1 file changed, 1 insertion(+) (limited to 'arch') diff --git a/arch/x86/net/bpf_jit_comp.c b/arch/x86/net/bpf_jit_comp.c index 8fe35ed11fd6..16b6efacf7c6 100644 --- a/arch/x86/net/bpf_jit_comp.c +++ b/arch/x86/net/bpf_jit_comp.c @@ -412,6 +412,7 @@ static void emit_indirect_jump(u8 **pprog, int reg, u8 *ip) EMIT_LFENCE(); EMIT2(0xFF, 0xE0 + reg); } else if (cpu_feature_enabled(X86_FEATURE_RETPOLINE)) { + OPTIMIZER_HIDE_VAR(reg); emit_jump(&prog, &__x86_indirect_thunk_array[reg], ip); } else #endif -- cgit v1.2.3 From 334865b2915c33080624e0d06f1c3e917036472c Mon Sep 17 00:00:00 2001 From: Nick Desaulniers Date: Tue, 29 Mar 2022 13:21:45 -0700 Subject: x86/extable: Prefer local labels in .set directives Bernardo reported an error that Nathan bisected down to (x86_64) defconfig+LTO_CLANG_FULL+X86_PMEM_LEGACY. LTO vmlinux.o ld.lld: error: :1:13: redefinition of 'found' .set found, 0 ^ :29:1: while in macro instantiation extable_type_reg reg=%eax, type=(17 | ((0) << 16)) ^ This appears to be another LTO specific issue similar to what was folded into commit 4b5305decc84 ("x86/extable: Extend extable functionality"), where the `.set found, 0` in DEFINE_EXTABLE_TYPE_REG in arch/x86/include/asm/asm.h conflicts with the symbol for the static function `found` in arch/x86/kernel/pmem.c. Assembler .set directive declare symbols with global visibility, so the assembler may not rename such symbols in the event of a conflict. LTO could rename static functions if there was a conflict in C sources, but it cannot see into symbols defined in inline asm. The symbols are also retained in the symbol table, regardless of LTO. Give the symbols .L prefixes making them locally visible, so that they may be renamed for LTO to avoid conflicts, and to drop them from the symbol table regardless of LTO. Fixes: 4b5305decc84 ("x86/extable: Extend extable functionality") Reported-by: Bernardo Meurer Costa Debugged-by: Nathan Chancellor Signed-off-by: Nick Desaulniers Signed-off-by: Peter Zijlstra (Intel) Reviewed-by: Nathan Chancellor Tested-by: Nathan Chancellor Link: https://lore.kernel.org/r/20220329202148.2379697-1-ndesaulniers@google.com --- arch/x86/include/asm/asm.h | 20 ++++++++++---------- 1 file changed, 10 insertions(+), 10 deletions(-) (limited to 'arch') diff --git a/arch/x86/include/asm/asm.h b/arch/x86/include/asm/asm.h index c878fed3056f..fbcfec4dc4cc 100644 --- a/arch/x86/include/asm/asm.h +++ b/arch/x86/include/asm/asm.h @@ -154,24 +154,24 @@ # define DEFINE_EXTABLE_TYPE_REG \ ".macro extable_type_reg type:req reg:req\n" \ - ".set found, 0\n" \ - ".set regnr, 0\n" \ + ".set .Lfound, 0\n" \ + ".set .Lregnr, 0\n" \ ".irp rs,rax,rcx,rdx,rbx,rsp,rbp,rsi,rdi,r8,r9,r10,r11,r12,r13,r14,r15\n" \ ".ifc \\reg, %%\\rs\n" \ - ".set found, found+1\n" \ - ".long \\type + (regnr << 8)\n" \ + ".set .Lfound, .Lfound+1\n" \ + ".long \\type + (.Lregnr << 8)\n" \ ".endif\n" \ - ".set regnr, regnr+1\n" \ + ".set .Lregnr, .Lregnr+1\n" \ ".endr\n" \ - ".set regnr, 0\n" \ + ".set .Lregnr, 0\n" \ ".irp rs,eax,ecx,edx,ebx,esp,ebp,esi,edi,r8d,r9d,r10d,r11d,r12d,r13d,r14d,r15d\n" \ ".ifc \\reg, %%\\rs\n" \ - ".set found, found+1\n" \ - ".long \\type + (regnr << 8)\n" \ + ".set .Lfound, .Lfound+1\n" \ + ".long \\type + (.Lregnr << 8)\n" \ ".endif\n" \ - ".set regnr, regnr+1\n" \ + ".set .Lregnr, .Lregnr+1\n" \ ".endr\n" \ - ".if (found != 1)\n" \ + ".if (.Lfound != 1)\n" \ ".error \"extable_type_reg: bad register argument\"\n" \ ".endif\n" \ ".endm\n" -- cgit v1.2.3 From 59b18a1e65b7a2134814106d0860010e10babe18 Mon Sep 17 00:00:00 2001 From: Reto Buerki Date: Thu, 7 Apr 2022 13:06:47 +0200 Subject: x86/msi: Fix msi message data shadow struct The x86 MSI message data is 32 bits in total and is either in compatibility or remappable format, see Intel Virtualization Technology for Directed I/O, section 5.1.2. Fixes: 6285aa50736 ("x86/msi: Provide msi message shadow structs") Co-developed-by: Adrian-Ken Rueegsegger Signed-off-by: Adrian-Ken Rueegsegger Signed-off-by: Reto Buerki Signed-off-by: Thomas Gleixner Cc: stable@vger.kernel.org Link: https://lore.kernel.org/r/20220407110647.67372-1-reet@codelabs.ch --- arch/x86/include/asm/msi.h | 19 +++++++++++-------- 1 file changed, 11 insertions(+), 8 deletions(-) (limited to 'arch') diff --git a/arch/x86/include/asm/msi.h b/arch/x86/include/asm/msi.h index b85147d75626..d71c7e8b738d 100644 --- a/arch/x86/include/asm/msi.h +++ b/arch/x86/include/asm/msi.h @@ -12,14 +12,17 @@ int pci_msi_prepare(struct irq_domain *domain, struct device *dev, int nvec, /* Structs and defines for the X86 specific MSI message format */ typedef struct x86_msi_data { - u32 vector : 8, - delivery_mode : 3, - dest_mode_logical : 1, - reserved : 2, - active_low : 1, - is_level : 1; - - u32 dmar_subhandle; + union { + struct { + u32 vector : 8, + delivery_mode : 3, + dest_mode_logical : 1, + reserved : 2, + active_low : 1, + is_level : 1; + }; + u32 dmar_subhandle; + }; } __attribute__ ((packed)) arch_msi_msg_data_t; #define arch_msi_msg_data x86_msi_data -- cgit v1.2.3