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-rw-r--r--arch/x86/kvm/Kconfig7
-rw-r--r--arch/x86/kvm/mmu/mmu.c42
-rw-r--r--arch/x86/kvm/svm/sev.c23
-rw-r--r--arch/x86/kvm/vmx/run_flags.h7
-rw-r--r--arch/x86/kvm/vmx/vmenter.S9
-rw-r--r--arch/x86/kvm/vmx/vmx.c20
-rw-r--r--arch/x86/kvm/x86.c12
7 files changed, 98 insertions, 22 deletions
diff --git a/arch/x86/kvm/Kconfig b/arch/x86/kvm/Kconfig
index 87e3da7b0439..65ed14b6540b 100644
--- a/arch/x86/kvm/Kconfig
+++ b/arch/x86/kvm/Kconfig
@@ -80,9 +80,10 @@ config KVM_SW_PROTECTED_VM
depends on KVM && X86_64
select KVM_GENERIC_PRIVATE_MEM
help
- Enable support for KVM software-protected VMs. Currently "protected"
- means the VM can be backed with memory provided by
- KVM_CREATE_GUEST_MEMFD.
+ Enable support for KVM software-protected VMs. Currently, software-
+ protected VMs are purely a development and testing vehicle for
+ KVM_CREATE_GUEST_MEMFD. Attempting to run a "real" VM workload as a
+ software-protected VM will fail miserably.
If unsure, say "N".
diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
index 2d6cdeab1f8a..0544700ca50b 100644
--- a/arch/x86/kvm/mmu/mmu.c
+++ b/arch/x86/kvm/mmu/mmu.c
@@ -4405,6 +4405,31 @@ static int kvm_faultin_pfn(struct kvm_vcpu *vcpu, struct kvm_page_fault *fault,
fault->mmu_seq = vcpu->kvm->mmu_invalidate_seq;
smp_rmb();
+ /*
+ * Check for a relevant mmu_notifier invalidation event before getting
+ * the pfn from the primary MMU, and before acquiring mmu_lock.
+ *
+ * For mmu_lock, if there is an in-progress invalidation and the kernel
+ * allows preemption, the invalidation task may drop mmu_lock and yield
+ * in response to mmu_lock being contended, which is *very* counter-
+ * productive as this vCPU can't actually make forward progress until
+ * the invalidation completes.
+ *
+ * Retrying now can also avoid unnessary lock contention in the primary
+ * MMU, as the primary MMU doesn't necessarily hold a single lock for
+ * the duration of the invalidation, i.e. faulting in a conflicting pfn
+ * can cause the invalidation to take longer by holding locks that are
+ * needed to complete the invalidation.
+ *
+ * Do the pre-check even for non-preemtible kernels, i.e. even if KVM
+ * will never yield mmu_lock in response to contention, as this vCPU is
+ * *guaranteed* to need to retry, i.e. waiting until mmu_lock is held
+ * to detect retry guarantees the worst case latency for the vCPU.
+ */
+ if (fault->slot &&
+ mmu_invalidate_retry_gfn_unsafe(vcpu->kvm, fault->mmu_seq, fault->gfn))
+ return RET_PF_RETRY;
+
ret = __kvm_faultin_pfn(vcpu, fault);
if (ret != RET_PF_CONTINUE)
return ret;
@@ -4415,6 +4440,18 @@ static int kvm_faultin_pfn(struct kvm_vcpu *vcpu, struct kvm_page_fault *fault,
if (unlikely(!fault->slot))
return kvm_handle_noslot_fault(vcpu, fault, access);
+ /*
+ * Check again for a relevant mmu_notifier invalidation event purely to
+ * avoid contending mmu_lock. Most invalidations will be detected by
+ * the previous check, but checking is extremely cheap relative to the
+ * overall cost of failing to detect the invalidation until after
+ * mmu_lock is acquired.
+ */
+ if (mmu_invalidate_retry_gfn_unsafe(vcpu->kvm, fault->mmu_seq, fault->gfn)) {
+ kvm_release_pfn_clean(fault->pfn);
+ return RET_PF_RETRY;
+ }
+
return RET_PF_CONTINUE;
}
@@ -4442,6 +4479,11 @@ static bool is_page_fault_stale(struct kvm_vcpu *vcpu,
if (!sp && kvm_test_request(KVM_REQ_MMU_FREE_OBSOLETE_ROOTS, vcpu))
return true;
+ /*
+ * Check for a relevant mmu_notifier invalidation event one last time
+ * now that mmu_lock is held, as the "unsafe" checks performed without
+ * holding mmu_lock can get false negatives.
+ */
return fault->slot &&
mmu_invalidate_retry_gfn(vcpu->kvm, fault->mmu_seq, fault->gfn);
}
diff --git a/arch/x86/kvm/svm/sev.c b/arch/x86/kvm/svm/sev.c
index f760106c31f8..a8ce5226b3b5 100644
--- a/arch/x86/kvm/svm/sev.c
+++ b/arch/x86/kvm/svm/sev.c
@@ -57,7 +57,7 @@ static bool sev_es_enabled = true;
module_param_named(sev_es, sev_es_enabled, bool, 0444);
/* enable/disable SEV-ES DebugSwap support */
-static bool sev_es_debug_swap_enabled = true;
+static bool sev_es_debug_swap_enabled = false;
module_param_named(debug_swap, sev_es_debug_swap_enabled, bool, 0444);
#else
#define sev_enabled false
@@ -612,8 +612,11 @@ static int sev_es_sync_vmsa(struct vcpu_svm *svm)
save->xss = svm->vcpu.arch.ia32_xss;
save->dr6 = svm->vcpu.arch.dr6;
- if (sev_es_debug_swap_enabled)
+ if (sev_es_debug_swap_enabled) {
save->sev_features |= SVM_SEV_FEAT_DEBUG_SWAP;
+ pr_warn_once("Enabling DebugSwap with KVM_SEV_ES_INIT. "
+ "This will not work starting with Linux 6.10\n");
+ }
pr_debug("Virtual Machine Save Area (VMSA):\n");
print_hex_dump_debug("", DUMP_PREFIX_NONE, 16, 1, save, sizeof(*save), false);
@@ -1975,20 +1978,22 @@ int sev_mem_enc_register_region(struct kvm *kvm,
goto e_free;
}
- region->uaddr = range->addr;
- region->size = range->size;
-
- list_add_tail(&region->list, &sev->regions_list);
- mutex_unlock(&kvm->lock);
-
/*
* The guest may change the memory encryption attribute from C=0 -> C=1
* or vice versa for this memory range. Lets make sure caches are
* flushed to ensure that guest data gets written into memory with
- * correct C-bit.
+ * correct C-bit. Note, this must be done before dropping kvm->lock,
+ * as region and its array of pages can be freed by a different task
+ * once kvm->lock is released.
*/
sev_clflush_pages(region->pages, region->npages);
+ region->uaddr = range->addr;
+ region->size = range->size;
+
+ list_add_tail(&region->list, &sev->regions_list);
+ mutex_unlock(&kvm->lock);
+
return ret;
e_free:
diff --git a/arch/x86/kvm/vmx/run_flags.h b/arch/x86/kvm/vmx/run_flags.h
index edc3f16cc189..6a9bfdfbb6e5 100644
--- a/arch/x86/kvm/vmx/run_flags.h
+++ b/arch/x86/kvm/vmx/run_flags.h
@@ -2,7 +2,10 @@
#ifndef __KVM_X86_VMX_RUN_FLAGS_H
#define __KVM_X86_VMX_RUN_FLAGS_H
-#define VMX_RUN_VMRESUME (1 << 0)
-#define VMX_RUN_SAVE_SPEC_CTRL (1 << 1)
+#define VMX_RUN_VMRESUME_SHIFT 0
+#define VMX_RUN_SAVE_SPEC_CTRL_SHIFT 1
+
+#define VMX_RUN_VMRESUME BIT(VMX_RUN_VMRESUME_SHIFT)
+#define VMX_RUN_SAVE_SPEC_CTRL BIT(VMX_RUN_SAVE_SPEC_CTRL_SHIFT)
#endif /* __KVM_X86_VMX_RUN_FLAGS_H */
diff --git a/arch/x86/kvm/vmx/vmenter.S b/arch/x86/kvm/vmx/vmenter.S
index 906ecd001511..2bfbf758d061 100644
--- a/arch/x86/kvm/vmx/vmenter.S
+++ b/arch/x86/kvm/vmx/vmenter.S
@@ -139,7 +139,7 @@ SYM_FUNC_START(__vmx_vcpu_run)
mov (%_ASM_SP), %_ASM_AX
/* Check if vmlaunch or vmresume is needed */
- test $VMX_RUN_VMRESUME, %ebx
+ bt $VMX_RUN_VMRESUME_SHIFT, %ebx
/* Load guest registers. Don't clobber flags. */
mov VCPU_RCX(%_ASM_AX), %_ASM_CX
@@ -161,8 +161,11 @@ SYM_FUNC_START(__vmx_vcpu_run)
/* Load guest RAX. This kills the @regs pointer! */
mov VCPU_RAX(%_ASM_AX), %_ASM_AX
- /* Check EFLAGS.ZF from 'test VMX_RUN_VMRESUME' above */
- jz .Lvmlaunch
+ /* Clobbers EFLAGS.ZF */
+ CLEAR_CPU_BUFFERS
+
+ /* Check EFLAGS.CF from the VMX_RUN_VMRESUME bit test above. */
+ jnc .Lvmlaunch
/*
* After a successful VMRESUME/VMLAUNCH, control flow "magically"
diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
index 1111d9d08903..88a4ff200d04 100644
--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -388,7 +388,16 @@ static __always_inline void vmx_enable_fb_clear(struct vcpu_vmx *vmx)
static void vmx_update_fb_clear_dis(struct kvm_vcpu *vcpu, struct vcpu_vmx *vmx)
{
- vmx->disable_fb_clear = (host_arch_capabilities & ARCH_CAP_FB_CLEAR_CTRL) &&
+ /*
+ * Disable VERW's behavior of clearing CPU buffers for the guest if the
+ * CPU isn't affected by MDS/TAA, and the host hasn't forcefully enabled
+ * the mitigation. Disabling the clearing behavior provides a
+ * performance boost for guests that aren't aware that manually clearing
+ * CPU buffers is unnecessary, at the cost of MSR accesses on VM-Entry
+ * and VM-Exit.
+ */
+ vmx->disable_fb_clear = !cpu_feature_enabled(X86_FEATURE_CLEAR_CPU_BUF) &&
+ (host_arch_capabilities & ARCH_CAP_FB_CLEAR_CTRL) &&
!boot_cpu_has_bug(X86_BUG_MDS) &&
!boot_cpu_has_bug(X86_BUG_TAA);
@@ -7224,11 +7233,14 @@ static noinstr void vmx_vcpu_enter_exit(struct kvm_vcpu *vcpu,
guest_state_enter_irqoff();
- /* L1D Flush includes CPU buffer clear to mitigate MDS */
+ /*
+ * L1D Flush includes CPU buffer clear to mitigate MDS, but VERW
+ * mitigation for MDS is done late in VMentry and is still
+ * executed in spite of L1D Flush. This is because an extra VERW
+ * should not matter much after the big hammer L1D Flush.
+ */
if (static_branch_unlikely(&vmx_l1d_should_flush))
vmx_l1d_flush(vcpu);
- else if (static_branch_unlikely(&mds_user_clear))
- mds_clear_cpu_buffers();
else if (static_branch_unlikely(&mmio_stale_data_clear) &&
kvm_arch_has_assigned_device(vcpu->kvm))
mds_clear_cpu_buffers();
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 48a61d283406..e02cc710f56d 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -4580,7 +4580,7 @@ static bool kvm_is_vm_type_supported(unsigned long type)
{
return type == KVM_X86_DEFAULT_VM ||
(type == KVM_X86_SW_PROTECTED_VM &&
- IS_ENABLED(CONFIG_KVM_SW_PROTECTED_VM) && tdp_enabled);
+ IS_ENABLED(CONFIG_KVM_SW_PROTECTED_VM) && tdp_mmu_enabled);
}
int kvm_vm_ioctl_check_extension(struct kvm *kvm, long ext)
@@ -8007,6 +8007,16 @@ static int emulator_cmpxchg_emulated(struct x86_emulate_ctxt *ctxt,
if (r < 0)
return X86EMUL_UNHANDLEABLE;
+
+ /*
+ * Mark the page dirty _before_ checking whether or not the CMPXCHG was
+ * successful, as the old value is written back on failure. Note, for
+ * live migration, this is unnecessarily conservative as CMPXCHG writes
+ * back the original value and the access is atomic, but KVM's ABI is
+ * that all writes are dirty logged, regardless of the value written.
+ */
+ kvm_vcpu_mark_page_dirty(vcpu, gpa_to_gfn(gpa));
+
if (r)
return X86EMUL_CMPXCHG_FAILED;
generated by cgit v1.2.3 (git 2.25.1) at 2024-06-30 10:50:20 +0000