[PATCH AUTOSEL 4.19 135/167] KVM: VMX: check CPUID before allowing read/write of IA32_XSS

[Sasha Levin]

From: Wanpeng Li <wanpengli@xxxxxxxxxxx>

[ Upstream commit 4d763b168e9c5c366b05812c7bba7662e5ea3669 ]

Raise #GP when guest read/write IA32_XSS, but the CPUID bits
say that it shouldn't exist.

Fixes: 203000993de5 (kvm: vmx: add MSR logic for XSAVES)
Reported-by: Xiaoyao Li <xiaoyao.li@xxxxxxxxxxxxxxx>
Reported-by: Tao Xu <tao3.xu@xxxxxxxxx>
Cc: Paolo Bonzini <pbonzini@xxxxxxxxxx>
Cc: Radim KrÄmÃÅ <rkrcmar@xxxxxxxxxx>
Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: Wanpeng Li <wanpengli@xxxxxxxxxxx>
Signed-off-by: Paolo Bonzini <pbonzini@xxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
 arch/x86/kvm/vmx.c | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
index 82253d31842a2..2938b4bcc9684 100644
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -4135,7 +4135,10 @@ static int vmx_get_msr(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
 		return vmx_get_vmx_msr(&vmx->nested.msrs, msr_info->index,
 				       &msr_info->data);
 	case MSR_IA32_XSS:
-		if (!vmx_xsaves_supported())
+		if (!vmx_xsaves_supported() ||
+		    (!msr_info->host_initiated &&
+		     !(guest_cpuid_has(vcpu, X86_FEATURE_XSAVE) &&
+		       guest_cpuid_has(vcpu, X86_FEATURE_XSAVES))))
 			return 1;
 		msr_info->data = vcpu->arch.ia32_xss;
 		break;
@@ -4302,7 +4305,10 @@ static int vmx_set_msr(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
 			return 1;
 		return vmx_set_vmx_msr(vcpu, msr_index, data);
 	case MSR_IA32_XSS:
-		if (!vmx_xsaves_supported())
+		if (!vmx_xsaves_supported() ||
+		    (!msr_info->host_initiated &&
+		     !(guest_cpuid_has(vcpu, X86_FEATURE_XSAVE) &&
+		       guest_cpuid_has(vcpu, X86_FEATURE_XSAVES))))
 			return 1;
 		/*
 		 * The only supported bit as of Skylake is bit 8, but
-- 
2.20.1