KVM: VMX: Execute WBINVD to keep data consistency with assigned devices

Some guest device driver may leverage the "Non-Snoop" I/O, and explicitly
WBINVD or CLFLUSH to a RAM space. Since migration may occur before WBINVD or
CLFLUSH, we need to maintain data consistency either by:
1: flushing cache (wbinvd) when the guest is scheduled out if there is no
wbinvd exit, or
2: execute wbinvd on all dirty physical CPUs when guest wbinvd exits.

Signed-off-by: Yaozu (Eddie) Dong <eddie.dong@intel.com>
Signed-off-by: Sheng Yang <sheng@linux.intel.com>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>

1 files changed, 41 insertions, 0 deletions

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 27322d341232..3d72fc067059 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -1783,8 +1783,28 @@ out:
         return r;
 }
 
+static void wbinvd_ipi(void *garbage)
+{
+        wbinvd();
+}
+
+static bool need_emulate_wbinvd(struct kvm_vcpu *vcpu)
+{
+        return vcpu->kvm->arch.iommu_domain &&
+                !(vcpu->kvm->arch.iommu_flags & KVM_IOMMU_CACHE_COHERENCY);
+}
+
 void kvm_arch_vcpu_load(struct kvm_vcpu *vcpu, int cpu)
 {
+        /* Address WBINVD may be executed by guest */
+        if (need_emulate_wbinvd(vcpu)) {
+                if (kvm_x86_ops->has_wbinvd_exit())
+                        cpumask_set_cpu(cpu, vcpu->arch.wbinvd_dirty_mask);
+                else if (vcpu->cpu != -1 && vcpu->cpu != cpu)
+                        smp_call_function_single(vcpu->cpu,
+                                        wbinvd_ipi, NULL, 1);
+        }
+
         kvm_x86_ops->vcpu_load(vcpu, cpu);
         if (unlikely(per_cpu(cpu_tsc_khz, cpu) == 0)) {
                 unsigned long khz = cpufreq_quick_get(cpu);
@@ -3660,6 +3680,21 @@ int emulate_invlpg(struct kvm_vcpu *vcpu, gva_t address)
         return X86EMUL_CONTINUE;
 }
 
+int kvm_emulate_wbinvd(struct kvm_vcpu *vcpu)
+{
+        if (!need_emulate_wbinvd(vcpu))
+                return X86EMUL_CONTINUE;
+
+        if (kvm_x86_ops->has_wbinvd_exit()) {
+                smp_call_function_many(vcpu->arch.wbinvd_dirty_mask,
+                                wbinvd_ipi, NULL, 1);
+                cpumask_clear(vcpu->arch.wbinvd_dirty_mask);
+        }
+        wbinvd();
+        return X86EMUL_CONTINUE;
+}
+EXPORT_SYMBOL_GPL(kvm_emulate_wbinvd);
+
 int emulate_clts(struct kvm_vcpu *vcpu)
 {
         kvm_x86_ops->set_cr0(vcpu, kvm_read_cr0_bits(vcpu, ~X86_CR0_TS));
@@ -5263,6 +5298,7 @@ void kvm_arch_vcpu_free(struct kvm_vcpu *vcpu)
                 vcpu->arch.time_page = NULL;
         }
 
+        free_cpumask_var(vcpu->arch.wbinvd_dirty_mask);
         fx_free(vcpu);
         kvm_x86_ops->vcpu_free(vcpu);
 }
@@ -5392,7 +5428,12 @@ int kvm_arch_vcpu_init(struct kvm_vcpu *vcpu)
         }
         vcpu->arch.mcg_cap = KVM_MAX_MCE_BANKS;
 
+        if (!zalloc_cpumask_var(&vcpu->arch.wbinvd_dirty_mask, GFP_KERNEL))
+                goto fail_free_mce_banks;
+
         return 0;
+fail_free_mce_banks:
+        kfree(vcpu->arch.mce_banks);
 fail_free_lapic:
         kvm_free_lapic(vcpu);
 fail_mmu_destroy: