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| author | Paolo Bonzini <pbonzini@redhat.com> | 2020-02-05 16:10:52 +0100 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2021-01-06 14:44:59 +0100 |
| commit | 88464279c03ce05b56abeed7c38c4064dd054ab9 (patch) | |
| tree | d1b75af5a032f0ee0ebad76a858e26eebfdac667 /arch | |
| parent | c1f49fb15943656d5e1a3bd696853ab3a954babb (diff) | |
| download | linux-stable-88464279c03ce05b56abeed7c38c4064dd054ab9.tar.gz linux-stable-88464279c03ce05b56abeed7c38c4064dd054ab9.tar.bz2 linux-stable-88464279c03ce05b56abeed7c38c4064dd054ab9.zip | |
KVM: SVM: relax conditions for allowing MSR_IA32_SPEC_CTRL accesses
[ Upstream commit df7e8818926eb4712b67421442acf7d568fe2645 ]
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>
Diffstat (limited to 'arch')
| -rw-r--r-- | arch/x86/kvm/svm.c | 4 |
1 files changed, 4 insertions, 0 deletions
diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c index a0c3d1b4b295..f513110983d4 100644 --- a/arch/x86/kvm/svm.c +++ b/arch/x86/kvm/svm.c @@ -4209,6 +4209,8 @@ 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; @@ -4312,6 +4314,8 @@ 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; |