Under the case of nested on nested (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.
Similarly we check if vcpu is under guest mode before emulating the
vmware-backdoor instructions. For the case of nested on nested, we
let the guest handle it.
Co-developed-by: Bandan Das <bsd@xxxxxxxxxx>
Signed-off-by: Bandan Das <bsd@xxxxxxxxxx>
Signed-off-by: Wei Huang <wei.huang2@xxxxxxx>
Tested-by: Maxim Levitsky <mlevitsk@xxxxxxxxxx>
Reviewed-by: Maxim Levitsky <mlevitsk@xxxxxxxxxx>
---
arch/x86/kvm/svm/svm.c | 20 ++++++++++++++++++--
1 file changed, 18 insertions(+), 2 deletions(-)
diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c
index f9233c79265b..83c401d2709f 100644
--- a/arch/x86/kvm/svm/svm.c
+++ b/arch/x86/kvm/svm/svm.c
@@ -929,6 +929,9 @@ static __init void svm_set_cpu_caps(void)
if (npt_enabled)
kvm_cpu_cap_set(X86_FEATURE_NPT);
+
+ /* Nested VM can receive #VMEXIT instead of triggering #GP */
+ kvm_cpu_cap_set(X86_FEATURE_SVME_ADDR_CHK);
}
/* CPUID 0x80000008 */
@@ -2198,6 +2201,11 @@ 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,
@@ -2205,7 +2213,14 @@ 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);
}
/*
@@ -2239,7 +2254,8 @@ static int gp_interception(struct vcpu_svm *svm)
* VMware backdoor emulation on #GP interception only handles
* IN{S}, OUT{S}, and RDPMC.
*/
- return kvm_emulate_instruction(vcpu,
+ if (!is_guest_mode(vcpu))
+ return kvm_emulate_instruction(vcpu,
EMULTYPE_VMWARE_GP | EMULTYPE_NO_DECODE);
} else
return emulate_svm_instr(vcpu, opcode);
--
2.27.0
