Do not update the new vmcb's last-run cpu when switching to a different
vmcb. If the vCPU is migrated between its last run and a vmcb switch,
e.g. for nested VM-Exit, then setting the cpu without marking the vmcb
dirty will lead to KVM running the vCPU on a different physical cpu with
stale clean bit settings.
vcpu->cpu current_vmcb->cpu hardware
pre_svm_run() cpu0 cpu0 cpu0,clean
kvm_arch_vcpu_load() cpu1 cpu0 cpu0,clean
svm_switch_vmcb() cpu1 cpu1 cpu0,clean
pre_svm_run() cpu1 cpu1 kaboom
Simply delete the offending code; unlike VMX, which needs to update the
cpu at switch time due to the need to do VMPTRLD, SVM only cares about
which cpu last ran the vCPU.
Fixes: af18fa775d07 ("KVM: nSVM: Track the physical cpu of the vmcb vmrun through the vmcb")
Cc: Cathy Avery <cavery@xxxxxxxxxx>
Signed-off-by: Sean Christopherson <seanjc@xxxxxxxxxx>
---
arch/x86/kvm/svm/svm.c | 8 --------
1 file changed, 8 deletions(-)
diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c
index 48b396f33bee..89619cc52cf4 100644
--- a/arch/x86/kvm/svm/svm.c
+++ b/arch/x86/kvm/svm/svm.c
@@ -1311,14 +1311,6 @@ void svm_switch_vmcb(struct vcpu_svm *svm, struct kvm_vmcb_info *target_vmcb)
svm->current_vmcb = target_vmcb;
svm->vmcb = target_vmcb->ptr;
svm->vmcb_pa = target_vmcb->pa;
-
- /*
- * Track the physical CPU the target_vmcb is running on
- * in order to mark the VMCB dirty if the cpu changes at
- * its next vmrun.
- */
-
- svm->current_vmcb->cpu = svm->vcpu.cpu;
}
static int svm_create_vcpu(struct kvm_vcpu *vcpu)
--
2.31.0.208.g409f899ff0-goog
