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x86/KVM/VMX: Expose SPEC_CTRL Bit(2) to the guest 

Expose the CPUID.7.EDX[31] bit to the guest, and also guard against various
combinations of SPEC_CTRL MSR values.

The handling of the MSR (to take into account the host value of SPEC_CTRL
Bit(2)) is taken care of in patch:

  KVM/SVM/VMX/x86/spectre_v2: Support the combination of guest and host IBRS

Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
Konrad Rzeszutek Wilk 2018-04-25 22:04:25 -04:00 committed by Thomas Gleixner
parent 764f3c2158
commit da39556f66
2 changed files with 6 additions and 4 deletions
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2
arch/x86/kvm/cpuid.c
View File

@ -407,7 +407,7 @@ static inline int __do_cpuid_ent(struct kvm_cpuid_entry2 *entry, u32 function,
/* cpuid 7.0.edx*/
const u32 kvm_cpuid_7_0_edx_x86_features =
F(AVX512_4VNNIW) | F(AVX512_4FMAPS) | F(SPEC_CTRL) |
F(AVX512_4VNNIW) | F(AVX512_4FMAPS) | F(SPEC_CTRL) | F(RDS) |
F(ARCH_CAPABILITIES);
/* all calls to cpuid_count() should be made on the same cpu */

8
arch/x86/kvm/vmx.c
View File

@ -3524,7 +3524,8 @@ static int vmx_get_msr(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
case MSR_IA32_SPEC_CTRL:
if (!msr_info->host_initiated &&
!guest_cpuid_has(vcpu, X86_FEATURE_IBRS) &&
!guest_cpuid_has(vcpu, X86_FEATURE_SPEC_CTRL))
!guest_cpuid_has(vcpu, X86_FEATURE_SPEC_CTRL) &&
!guest_cpuid_has(vcpu, X86_FEATURE_RDS))
return 1;
msr_info->data = to_vmx(vcpu)->spec_ctrl;
@ -3643,11 +3644,12 @@ static int vmx_set_msr(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
case MSR_IA32_SPEC_CTRL:
if (!msr_info->host_initiated &&
!guest_cpuid_has(vcpu, X86_FEATURE_IBRS) &&
!guest_cpuid_has(vcpu, X86_FEATURE_SPEC_CTRL))
!guest_cpuid_has(vcpu, X86_FEATURE_SPEC_CTRL) &&
!guest_cpuid_has(vcpu, X86_FEATURE_RDS))
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_RDS))
return 1;
vmx->spec_ctrl = data;