Uh, thanks for your prompt response.
On 17/1/2022 4:31 pm, Paolo Bonzini wrote:
On 1/17/22 08:24, Like Xu wrote:
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 76b4803dd3bd..7d8622e592bb 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -1024,7 +1024,11 @@ static int __kvm_set_xcr(struct kvm_vcpu *vcpu, u32
index, u64 xcr)
int kvm_emulate_xsetbv(struct kvm_vcpu *vcpu)
{
- if (static_call(kvm_x86_get_cpl)(vcpu) != 0 ||
+ if (!guest_cpuid_has(vcpu, X86_FEATURE_XSAVE) ||
+ !kvm_read_cr4_bits(vcpu, X86_CR4_OSXSAVE))
+ return kvm_handle_invalid_op(vcpu);
There's no need to check XSAVE, because it XSAVE=0 will prevent setting
CR4.OSXSAVE.
So we just need to check X86_CR4_OSXSAVE for #UD here ?
Likewise, CPL and SS.DPL are also defined in real mode so there's no need to
check is_protmode. The Intel manuals sometimes still act as the descriptor
caches don't exist, even though VMX effectively made them part of the architecture.
OK, make sense to drop is_protmode().
Also, the "Fixes" tag is not really correct as the behavior was the same
before. Rather, it fixes commit 02d4160fbd76 ("x86: KVM: add xsetbv to the
It seems the original code comes from 81dd35d42c9a ("KVM: SVM: Add xsetbv
intercept").
2acf923e38 ("KVM: VMX: Enable XSAVE/XRSTOR for guest") and 92f9895c146d.
emulator", 2019-08-22). Checking OSXSAVE is a bug in the emulator path, even
though it's not needed in the XSETBV vmexit case.
The kvm_emulate_xsetbv() has been removed from the emulator path.
I'm not really sure why it's not needed in the XSETBV vmexit case. More details ?
Thanks,
Paolo
+ if ((is_protmode(vcpu) && static_call(kvm_x86_get_cpl)(vcpu) != 0) ||
__kvm_set_xcr(vcpu, kvm_rcx_read(vcpu), kvm_read_edx_eax(vcpu))) {
kvm_inject_gp(vcpu, 0);
return 1;
