Under the case of nested on nested (e.g. L0->L1->L2->L3), #GP triggered
by SVM instructions can be hided from L1. Instead the hypervisor can
inject the proper #VMEXIT to inform L1 of what is happening. Thus L1
can avoid invoking the #GP workaround. For this reason we turns on
guest VM's X86_FEATURE_SVME_ADDR_CHK bit for KVM running inside VM to
receive the notification and change behavior.
Co-developed-by: Bandan Das <bsd@xxxxxxxxxx>
Signed-off-by: Bandan Das <bsd@xxxxxxxxxx>
Signed-off-by: Wei Huang <wei.huang2@xxxxxxx>
---
arch/x86/kvm/svm/svm.c | 19 ++++++++++++++++++-
1 file changed, 18 insertions(+), 1 deletion(-)
diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c
index 2a12870ac71a..89512c0e7663 100644
--- a/arch/x86/kvm/svm/svm.c
+++ b/arch/x86/kvm/svm/svm.c
@@ -2196,6 +2196,11 @@ static int svm_instr_opcode(struct kvm_vcpu *vcpu)
static int emulate_svm_instr(struct kvm_vcpu *vcpu, int opcode)
{
+ const int guest_mode_exit_codes[] = {
+ [SVM_INSTR_VMRUN] = SVM_EXIT_VMRUN,
+ [SVM_INSTR_VMLOAD] = SVM_EXIT_VMLOAD,
+ [SVM_INSTR_VMSAVE] = SVM_EXIT_VMSAVE,
+ };
int (*const svm_instr_handlers[])(struct vcpu_svm *svm) = {
[SVM_INSTR_VMRUN] = vmrun_interception,
[SVM_INSTR_VMLOAD] = vmload_interception,
@@ -2203,7 +2208,14 @@ static int emulate_svm_instr(struct kvm_vcpu *vcpu, int opcode)
};
struct vcpu_svm *svm = to_svm(vcpu);
- return svm_instr_handlers[opcode](svm);
+ if (is_guest_mode(vcpu)) {
+ svm->vmcb->control.exit_code = guest_mode_exit_codes[opcode];
+ svm->vmcb->control.exit_info_1 = 0;
+ svm->vmcb->control.exit_info_2 = 0;
+
+ return nested_svm_vmexit(svm);
+ } else
+ return svm_instr_handlers[opcode](svm);
}
/*
@@ -4034,6 +4046,11 @@ static void svm_vcpu_after_set_cpuid(struct kvm_vcpu *vcpu)
/* Check again if INVPCID interception if required */
svm_check_invpcid(svm);
+ if (nested && guest_cpuid_has(vcpu, X86_FEATURE_SVM)) {
+ best = kvm_find_cpuid_entry(vcpu, 0x8000000A, 0);
+ best->edx |= (1 << 28);
+ }
+
/* For sev guests, the memory encryption bit is not reserved in CR3. */
if (sev_guest(vcpu->kvm)) {
best = kvm_find_cpuid_entry(vcpu, 0x8000001F, 0);
--
2.27.0
