redonkable
/
alistair23-linux
1
0
Fork 0
Code Releases Activity

KVM: SVM: relax conditions for allowing MSR_IA32_SPEC_CTRL accesses 

[ Upstream commit df7e881892 ]

Userspace that does not know about the AMD_IBRS bit might still
allow the guest to protect itself with MSR_IA32_SPEC_CTRL using
the Intel SPEC_CTRL bit.  However, svm.c disallows this and will
cause a #GP in the guest when writing to the MSR.  Fix this by
loosening the test and allowing the Intel CPUID bit, and in fact
allow the AMD_STIBP bit as well since it allows writing to
MSR_IA32_SPEC_CTRL too.

Reported-by: Zhiyi Guo <zhguo@redhat.com>
Analyzed-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
Analyzed-by: Laszlo Ersek <lersek@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
5.4-rM2-2.2.x-imx-squashed
Paolo Bonzini 2020-02-05 16:10:52 +01:00 committed by Greg Kroah-Hartman
parent d77c1ab54c
commit 3d4a058945
1 changed files with 4 additions and 0 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

4
arch/x86/kvm/svm.c
View File

@ -4233,6 +4233,8 @@ static int svm_get_msr(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
break;
case MSR_IA32_SPEC_CTRL:
if (!msr_info->host_initiated &&
!guest_cpuid_has(vcpu, X86_FEATURE_SPEC_CTRL) &&
!guest_cpuid_has(vcpu, X86_FEATURE_AMD_STIBP) &&
!guest_cpuid_has(vcpu, X86_FEATURE_AMD_IBRS) &&
!guest_cpuid_has(vcpu, X86_FEATURE_AMD_SSBD))
return 1;
@ -4318,6 +4320,8 @@ static int svm_set_msr(struct kvm_vcpu *vcpu, struct msr_data *msr)
break;
case MSR_IA32_SPEC_CTRL:
if (!msr->host_initiated &&
!guest_cpuid_has(vcpu, X86_FEATURE_SPEC_CTRL) &&
!guest_cpuid_has(vcpu, X86_FEATURE_AMD_STIBP) &&
!guest_cpuid_has(vcpu, X86_FEATURE_AMD_IBRS) &&
!guest_cpuid_has(vcpu, X86_FEATURE_AMD_SSBD))
return 1;