diff options
| author | Konrad Rzeszutek Wilk <konrad.wilk@oracle.com> | 2018-06-01 10:59:20 -0400 |
|---|---|---|
| committer | Thomas Gleixner <tglx@linutronix.de> | 2018-06-06 14:13:16 +0200 |
| commit | 6ac2f49edb1ef5446089c7c660017732886d62d6 (patch) | |
| tree | 58da02208899e2013269dc246c7d22fd279494ad /arch/x86/kvm | |
| parent | 24809860012e0130fbafe536709e08a22b3e959e (diff) | |
x86/bugs: Add AMD's SPEC_CTRL MSR usage
The AMD document outlining the SSBD handling
124441_AMD64_SpeculativeStoreBypassDisable_Whitepaper_final.pdf
mentions that if CPUID 8000_0008.EBX[24] is set we should be using
the SPEC_CTRL MSR (0x48) over the VIRT SPEC_CTRL MSR (0xC001_011f)
for speculative store bypass disable.
This in effect means we should clear the X86_FEATURE_VIRT_SSBD
flag so that we would prefer the SPEC_CTRL MSR.
See the document titled:
124441_AMD64_SpeculativeStoreBypassDisable_Whitepaper_final.pdf
A copy of this document is available at
https://bugzilla.kernel.org/show_bug.cgi?id=199889
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Tom Lendacky <thomas.lendacky@amd.com>
Cc: Janakarajan Natarajan <Janakarajan.Natarajan@amd.com>
Cc: kvm@vger.kernel.org
Cc: KarimAllah Ahmed <karahmed@amazon.de>
Cc: andrew.cooper3@citrix.com
Cc: Joerg Roedel <joro@8bytes.org>
Cc: Radim Krčmář <rkrcmar@redhat.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Borislav Petkov <bp@suse.de>
Cc: David Woodhouse <dwmw@amazon.co.uk>
Cc: Kees Cook <keescook@chromium.org>
Link: https://lkml.kernel.org/r/20180601145921.9500-3-konrad.wilk@oracle.com
Diffstat (limited to 'arch/x86/kvm')
| -rw-r--r-- | arch/x86/kvm/cpuid.c | 10 | ||||
| -rw-r--r-- | arch/x86/kvm/svm.c | 8 |
2 files changed, 13 insertions, 5 deletions
diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c index 132f8a58692e..f4f30d0c25c4 100644 --- a/arch/x86/kvm/cpuid.c +++ b/arch/x86/kvm/cpuid.c @@ -379,7 +379,8 @@ static inline int __do_cpuid_ent(struct kvm_cpuid_entry2 *entry, u32 function, /* cpuid 0x80000008.ebx */ const u32 kvm_cpuid_8000_0008_ebx_x86_features = - F(AMD_IBPB) | F(AMD_IBRS) | F(VIRT_SSBD) | F(AMD_SSB_NO); + F(AMD_IBPB) | F(AMD_IBRS) | F(AMD_SSBD) | F(VIRT_SSBD) | + F(AMD_SSB_NO); /* cpuid 0xC0000001.edx */ const u32 kvm_cpuid_C000_0001_edx_x86_features = @@ -664,7 +665,12 @@ static inline int __do_cpuid_ent(struct kvm_cpuid_entry2 *entry, u32 function, entry->ebx |= F(VIRT_SSBD); entry->ebx &= kvm_cpuid_8000_0008_ebx_x86_features; cpuid_mask(&entry->ebx, CPUID_8000_0008_EBX); - if (boot_cpu_has(X86_FEATURE_LS_CFG_SSBD)) + /* + * The preference is to use SPEC CTRL MSR instead of the + * VIRT_SPEC MSR. + */ + if (boot_cpu_has(X86_FEATURE_LS_CFG_SSBD) && + !boot_cpu_has(X86_FEATURE_AMD_SSBD)) entry->ebx |= F(VIRT_SSBD); break; } diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c index 26110c202b19..950ec50f77c3 100644 --- a/arch/x86/kvm/svm.c +++ b/arch/x86/kvm/svm.c @@ -4115,7 +4115,8 @@ 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_AMD_IBRS)) + !guest_cpuid_has(vcpu, X86_FEATURE_AMD_IBRS) && + !guest_cpuid_has(vcpu, X86_FEATURE_AMD_SSBD)) return 1; msr_info->data = svm->spec_ctrl; @@ -4217,11 +4218,12 @@ 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_AMD_IBRS)) + !guest_cpuid_has(vcpu, X86_FEATURE_AMD_IBRS) && + !guest_cpuid_has(vcpu, X86_FEATURE_AMD_SSBD)) return 1; /* The STIBP bit doesn't fault even if it's not advertised */ - if (data & ~(SPEC_CTRL_IBRS | SPEC_CTRL_STIBP)) + if (data & ~(SPEC_CTRL_IBRS | SPEC_CTRL_STIBP | SPEC_CTRL_SSBD)) return 1; svm->spec_ctrl = data; |