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Subject[PATCH 4.14 59/95] x86/KVM/VMX: Expose SPEC_CTRL Bit(2) to the guest
Date
4.14-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>

commit da39556f66f5cfe8f9c989206974f1cb16ca5d7c upstream

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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
arch/x86/kvm/cpuid.c | 2 +-
arch/x86/kvm/vmx.c | 8 +++++---
2 files changed, 6 insertions(+), 4 deletions(-)

--- a/arch/x86/kvm/cpuid.c
+++ b/arch/x86/kvm/cpuid.c
@@ -394,7 +394,7 @@ static inline int __do_cpuid_ent(struct

/* 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 */
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -3294,7 +3294,8 @@ static int vmx_get_msr(struct kvm_vcpu *
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;
@@ -3415,11 +3416,12 @@ static int vmx_set_msr(struct kvm_vcpu *
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;

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