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SubjectRe: [PATCH v2 4/4] x86: vmx: Allow direct access to MSR_IA32_ARCH_CAPABILITIES
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On 01/29/2018 07:55 PM, Jim Mattson wrote:
> Why should this MSR be pass-through? I doubt that it would be accessed
> frequently.

True. Will update it to be emulated and allow user-space to set the
value exposed.

>
> On Sun, Jan 28, 2018 at 4:58 PM, KarimAllah Ahmed <karahmed@amazon.de> wrote:
>> Add direct access to MSR_IA32_SPEC_CTRL for guests. Future intel processors
>> will use this MSR to indicate RDCL_NO (bit 0) and IBRS_ALL (bit 1).
>>
>> Cc: Asit Mallick <asit.k.mallick@intel.com>
>> Cc: Dave Hansen <dave.hansen@intel.com>
>> Cc: Arjan Van De Ven <arjan.van.de.ven@intel.com>
>> Cc: Tim Chen <tim.c.chen@linux.intel.com>
>> Cc: Linus Torvalds <torvalds@linux-foundation.org>
>> Cc: Andrea Arcangeli <aarcange@redhat.com>
>> Cc: Andi Kleen <ak@linux.intel.com>
>> Cc: Thomas Gleixner <tglx@linutronix.de>
>> Cc: Dan Williams <dan.j.williams@intel.com>
>> Cc: Jun Nakajima <jun.nakajima@intel.com>
>> Cc: Andy Lutomirski <luto@kernel.org>
>> Cc: Greg KH <gregkh@linuxfoundation.org>
>> Cc: Paolo Bonzini <pbonzini@redhat.com>
>> Cc: Ashok Raj <ashok.raj@intel.com>
>> Signed-off-by: KarimAllah Ahmed <karahmed@amazon.de>
>> ---
>> arch/x86/kvm/cpuid.c | 4 +++-
>> arch/x86/kvm/vmx.c | 2 ++
>> 2 files changed, 5 insertions(+), 1 deletion(-)
>>
>> diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c
>> index 32c0c14..2339b1a 100644
>> --- a/arch/x86/kvm/cpuid.c
>> +++ b/arch/x86/kvm/cpuid.c
>> @@ -71,6 +71,7 @@ u64 kvm_supported_xcr0(void)
>> #define KVM_CPUID_BIT_AVX512_4VNNIW 2
>> #define KVM_CPUID_BIT_AVX512_4FMAPS 3
>> #define KVM_CPUID_BIT_IBRS 26
>> +#define KVM_CPUID_BIT_ARCH_CAPABILITIES 29
>> #define KF(x) bit(KVM_CPUID_BIT_##x)
>>
>> int kvm_update_cpuid(struct kvm_vcpu *vcpu)
>> @@ -394,7 +395,8 @@ 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 =
>> KF(AVX512_4VNNIW) | KF(AVX512_4FMAPS) | \
>> - (boot_cpu_has(X86_FEATURE_IBRS) ? KF(IBRS) : 0);
>> + (boot_cpu_has(X86_FEATURE_IBRS) ? KF(IBRS) : 0) | \
>> + (boot_cpu_has(X86_FEATURE_ARCH_CAPABILITIES) ? KF(ARCH_CAPABILITIES) : 0);
>>
>> /* all calls to cpuid_count() should be made on the same cpu */
>> get_cpu();
>> diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
>> index f82a44c..99cb761 100644
>> --- a/arch/x86/kvm/vmx.c
>> +++ b/arch/x86/kvm/vmx.c
>> @@ -9617,6 +9617,8 @@ static struct kvm_vcpu *vmx_create_vcpu(struct kvm *kvm, unsigned int id)
>>
>> if (boot_cpu_has(X86_FEATURE_IBPB))
>> vmx_disable_intercept_for_msr(msr_bitmap, MSR_IA32_PRED_CMD, MSR_TYPE_RW);
>> + if (boot_cpu_has(X86_FEATURE_ARCH_CAPABILITIES))
>> + vmx_disable_intercept_for_msr(msr_bitmap, MSR_IA32_ARCH_CAPABILITIES, MSR_TYPE_R);
>> vmx_disable_intercept_for_msr(msr_bitmap, MSR_FS_BASE, MSR_TYPE_RW);
>> vmx_disable_intercept_for_msr(msr_bitmap, MSR_GS_BASE, MSR_TYPE_RW);
>> vmx_disable_intercept_for_msr(msr_bitmap, MSR_KERNEL_GS_BASE, MSR_TYPE_RW);
>> --
>> 2.7.4
>>
>
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