KVM: CPUID: Add new features to the guest's CPUID
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Message ID 20190715210316.25569-1-aaronlewis@google.com
State New
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  • KVM: CPUID: Add new features to the guest's CPUID
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Commit Message

Aaron Lewis July 15, 2019, 9:03 p.m. UTC
Add features X86_FEATURE_FDP_EXCPTN_ONLY and X86_FEATURE_ZERO_FCS_FDS to the
mask for CPUID.(EAX=07H,ECX=0H):EBX.  Doing this will ensure the guest's CPUID
for these bits match the host, rather than the guest being blindly set to 0.

This is important as these are actually defeature bits, which means that
a 0 indicates the presence of a feature and a 1 indicates the absence of
a feature.  since these features cannot be emulated, kvm should not
claim the existence of a feature that isn't present on the host.

Signed-off-by: Aaron Lewis <aaronlewis@google.com>
---
 arch/x86/kvm/cpuid.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

Comments

Aaron Lewis July 22, 2019, 2:51 p.m. UTC | #1
On Mon, Jul 15, 2019 at 2:03 PM Aaron Lewis <aaronlewis@google.com> wrote:
>
> Add features X86_FEATURE_FDP_EXCPTN_ONLY and X86_FEATURE_ZERO_FCS_FDS to the
> mask for CPUID.(EAX=07H,ECX=0H):EBX.  Doing this will ensure the guest's CPUID
> for these bits match the host, rather than the guest being blindly set to 0.
>
> This is important as these are actually defeature bits, which means that
> a 0 indicates the presence of a feature and a 1 indicates the absence of
> a feature.  since these features cannot be emulated, kvm should not
> claim the existence of a feature that isn't present on the host.
>
> Signed-off-by: Aaron Lewis <aaronlewis@google.com>
> ---
>  arch/x86/kvm/cpuid.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c
> index ead681210306..64c3fad068e1 100644
> --- a/arch/x86/kvm/cpuid.c
> +++ b/arch/x86/kvm/cpuid.c
> @@ -353,7 +353,8 @@ static inline void do_cpuid_7_mask(struct kvm_cpuid_entry2 *entry, int index)
>                 F(BMI2) | F(ERMS) | f_invpcid | F(RTM) | f_mpx | F(RDSEED) |
>                 F(ADX) | F(SMAP) | F(AVX512IFMA) | F(AVX512F) | F(AVX512PF) |
>                 F(AVX512ER) | F(AVX512CD) | F(CLFLUSHOPT) | F(CLWB) | F(AVX512DQ) |
> -               F(SHA_NI) | F(AVX512BW) | F(AVX512VL) | f_intel_pt;
> +               F(SHA_NI) | F(AVX512BW) | F(AVX512VL) | f_intel_pt |
> +               F(FDP_EXCPTN_ONLY) | F(ZERO_FCS_FDS);
>
>         /* cpuid 7.0.ecx*/
>         const u32 kvm_cpuid_7_0_ecx_x86_features =
> --
> 2.22.0.510.g264f2c817a-goog
>

ping
Krish Sadhukhan July 23, 2019, 9:42 p.m. UTC | #2
On 07/15/2019 02:03 PM, Aaron Lewis wrote:
> Add features X86_FEATURE_FDP_EXCPTN_ONLY and X86_FEATURE_ZERO_FCS_FDS to the
> mask for CPUID.(EAX=07H,ECX=0H):EBX.  Doing this will ensure the guest's CPUID
> for these bits match the host, rather than the guest being blindly set to 0.
>
> This is important as these are actually defeature bits, which means that
> a 0 indicates the presence of a feature and a 1 indicates the absence of
> a feature.  since these features cannot be emulated, kvm should not
> claim the existence of a feature that isn't present on the host.
>
> Signed-off-by: Aaron Lewis <aaronlewis@google.com>
> ---
>   arch/x86/kvm/cpuid.c | 3 ++-
>   1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c
> index ead681210306..64c3fad068e1 100644
> --- a/arch/x86/kvm/cpuid.c
> +++ b/arch/x86/kvm/cpuid.c
> @@ -353,7 +353,8 @@ static inline void do_cpuid_7_mask(struct kvm_cpuid_entry2 *entry, int index)
>   		F(BMI2) | F(ERMS) | f_invpcid | F(RTM) | f_mpx | F(RDSEED) |
>   		F(ADX) | F(SMAP) | F(AVX512IFMA) | F(AVX512F) | F(AVX512PF) |
>   		F(AVX512ER) | F(AVX512CD) | F(CLFLUSHOPT) | F(CLWB) | F(AVX512DQ) |
> -		F(SHA_NI) | F(AVX512BW) | F(AVX512VL) | f_intel_pt;
> +		F(SHA_NI) | F(AVX512BW) | F(AVX512VL) | f_intel_pt |
> +		F(FDP_EXCPTN_ONLY) | F(ZERO_FCS_FDS);
>   
>   	/* cpuid 7.0.ecx*/
>   	const u32 kvm_cpuid_7_0_ecx_x86_features =

Reviewed-by: Krish Sadhukhan <krish.sadhukhan@oracle.com>
Aaron Lewis Aug. 21, 2019, 4:17 p.m. UTC | #3
On Tue, Jul 23, 2019 at 2:42 PM Krish Sadhukhan
<krish.sadhukhan@oracle.com> wrote:
>
>
>
> On 07/15/2019 02:03 PM, Aaron Lewis wrote:
> > Add features X86_FEATURE_FDP_EXCPTN_ONLY and X86_FEATURE_ZERO_FCS_FDS to the
> > mask for CPUID.(EAX=07H,ECX=0H):EBX.  Doing this will ensure the guest's CPUID
> > for these bits match the host, rather than the guest being blindly set to 0.
> >
> > This is important as these are actually defeature bits, which means that
> > a 0 indicates the presence of a feature and a 1 indicates the absence of
> > a feature.  since these features cannot be emulated, kvm should not
> > claim the existence of a feature that isn't present on the host.
> >
> > Signed-off-by: Aaron Lewis <aaronlewis@google.com>
> > Reviewed-by: Krish Sadhukhan <krish.sadhukhan@oracle.com>
> > ---
> >   arch/x86/kvm/cpuid.c | 3 ++-
> >   1 file changed, 2 insertions(+), 1 deletion(-)
> >
> > diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c
> > index ead681210306..64c3fad068e1 100644
> > --- a/arch/x86/kvm/cpuid.c
> > +++ b/arch/x86/kvm/cpuid.c
> > @@ -353,7 +353,8 @@ static inline void do_cpuid_7_mask(struct kvm_cpuid_entry2 *entry, int index)
> >               F(BMI2) | F(ERMS) | f_invpcid | F(RTM) | f_mpx | F(RDSEED) |
> >               F(ADX) | F(SMAP) | F(AVX512IFMA) | F(AVX512F) | F(AVX512PF) |
> >               F(AVX512ER) | F(AVX512CD) | F(CLFLUSHOPT) | F(CLWB) | F(AVX512DQ) |
> > -             F(SHA_NI) | F(AVX512BW) | F(AVX512VL) | f_intel_pt;
> > +             F(SHA_NI) | F(AVX512BW) | F(AVX512VL) | f_intel_pt |
> > +             F(FDP_EXCPTN_ONLY) | F(ZERO_FCS_FDS);
> >
> >       /* cpuid 7.0.ecx*/
> >       const u32 kvm_cpuid_7_0_ecx_x86_features =
>
> Reviewed-by: Krish Sadhukhan <krish.sadhukhan@oracle.com>

ping

Patch
diff mbox series

diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c
index ead681210306..64c3fad068e1 100644
--- a/arch/x86/kvm/cpuid.c
+++ b/arch/x86/kvm/cpuid.c
@@ -353,7 +353,8 @@  static inline void do_cpuid_7_mask(struct kvm_cpuid_entry2 *entry, int index)
 		F(BMI2) | F(ERMS) | f_invpcid | F(RTM) | f_mpx | F(RDSEED) |
 		F(ADX) | F(SMAP) | F(AVX512IFMA) | F(AVX512F) | F(AVX512PF) |
 		F(AVX512ER) | F(AVX512CD) | F(CLFLUSHOPT) | F(CLWB) | F(AVX512DQ) |
-		F(SHA_NI) | F(AVX512BW) | F(AVX512VL) | f_intel_pt;
+		F(SHA_NI) | F(AVX512BW) | F(AVX512VL) | f_intel_pt |
+		F(FDP_EXCPTN_ONLY) | F(ZERO_FCS_FDS);
 
 	/* cpuid 7.0.ecx*/
 	const u32 kvm_cpuid_7_0_ecx_x86_features =