[PATCH] Fix SSBD not being exposed to guests. (v1)

[PATCH] Fix SSBD not being exposed to guests. (v1)

[Konrad Rzeszutek Wilk]

Hi,

Without this patch, when launching QEMU with -cpu +ssbd I ended up
with a warning seeing that the CPU does not support - which in fact it does.

The issue was the X86_FEATURE_ -  the kvm_cpuid_7_0_edx_x86_features
had bit 17 set (X86_FEATURE_SSBD), while the right bit should have been
bit 31 ( X86_FEATURE_SPEC_CTRL_SSBD). That meant the masking:

	entry->edx &= kvm_cpuid_7_0_edx_x86_features;

would nicely clear the SSBD bit.

This fixes:
Fixes: 52817587e706 ("x86/cpufeatures: Disentangle SSBD enumeration")

 arch/x86/kvm/cpuid.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

Konrad Rzeszutek Wilk (1):
      KVM: VMX: Expose SSBD properly to guests.

[PATCH] KVM: VMX: Expose SSBD properly to guests.

[Konrad Rzeszutek Wilk]

The X86_FEATURE_SSBD is an synthetic CPU feature - that is
it bit location has no relevance to the real CPUID 0x7.EBX[31]
bit position. For that we need the new CPU feature name.

Fixes: 52817587e706 ("x86/cpufeatures: Disentangle SSBD enumeration")

CC: Paolo Bonzini <pbonzini@redhat.com>
Cc: "Radim Krčmář" <rkrcmar@redhat.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: stable@vger.kernel.org
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
---
 arch/x86/kvm/cpuid.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c
index ced851169730..598461e24be3 100644
--- a/arch/x86/kvm/cpuid.c
+++ b/arch/x86/kvm/cpuid.c
@@ -407,8 +407,8 @@ 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 =
-		F(AVX512_4VNNIW) | F(AVX512_4FMAPS) | F(SPEC_CTRL) | F(SSBD) |
-		F(ARCH_CAPABILITIES);
+		F(AVX512_4VNNIW) | F(AVX512_4FMAPS) | F(SPEC_CTRL) |
+		F(SPEC_CTRL_SSBD) | F(ARCH_CAPABILITIES);
 
 	/* all calls to cpuid_count() should be made on the same cpu */
 	get_cpu();
-- 
2.13.4

Re: [PATCH] KVM: VMX: Expose SSBD properly to guests.

[Ben Hutchings]

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On Mon, 2018-05-21 at 17:54 -0400, Konrad Rzeszutek Wilk wrote:
> The X86_FEATURE_SSBD is an synthetic CPU feature - that is
> it bit location has no relevance to the real CPUID 0x7.EBX[31]
> bit position. For that we need the new CPU feature name.
> 
> Fixes: 52817587e706 ("x86/cpufeatures: Disentangle SSBD enumeration")
> 
> CC: Paolo Bonzini <pbonzini@redhat.com>
> Cc: "Radim Krčmář" <rkrcmar@redhat.com>
> Cc: Thomas Gleixner <tglx@linutronix.de>
> Cc: Ingo Molnar <mingo@redhat.com>
> Cc: "H. Peter Anvin" <hpa@zytor.com>
> Cc: stable@vger.kernel.org
> Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
> ---
>  arch/x86/kvm/cpuid.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c
> index ced851169730..598461e24be3 100644
> --- a/arch/x86/kvm/cpuid.c
> +++ b/arch/x86/kvm/cpuid.c
> @@ -407,8 +407,8 @@ 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 =
> -		F(AVX512_4VNNIW) | F(AVX512_4FMAPS) | F(SPEC_CTRL) | F(SSBD) |
> -		F(ARCH_CAPABILITIES);
> +		F(AVX512_4VNNIW) | F(AVX512_4FMAPS) | F(SPEC_CTRL) |
> +		F(SPEC_CTRL_SSBD) | F(ARCH_CAPABILITIES);
>  
>  	/* all calls to cpuid_count() should be made on the same cpu */
>  	get_cpu();

For 4.9-stable, guest_cpuid_has_spec_ctrl() needs a similar fix.

Ben.

-- 
Ben Hutchings
It is easier to change the specification to fit the program
than vice versa.

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[tip:x86/pti] KVM/VMX: Expose SSBD properly to guests

[tip-bot for Konrad Rzeszutek Wilk]

Commit-ID:  0aa48468d00959c8a37cd3ac727284f4f7359151
Gitweb:     https://git.kernel.org/tip/0aa48468d00959c8a37cd3ac727284f4f7359151
Author:     Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
AuthorDate: Mon, 21 May 2018 17:54:49 -0400
Committer:  Thomas Gleixner <tglx@linutronix.de>
CommitDate: Wed, 23 May 2018 10:55:52 +0200

KVM/VMX: Expose SSBD properly to guests

The X86_FEATURE_SSBD is an synthetic CPU feature - that is
it bit location has no relevance to the real CPUID 0x7.EBX[31]
bit position. For that we need the new CPU feature name.

Fixes: 52817587e706 ("x86/cpufeatures: Disentangle SSBD enumeration")
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: kvm@vger.kernel.org
Cc: "Radim Krčmář" <rkrcmar@redhat.com>
Cc: stable@vger.kernel.org
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Link: https://lkml.kernel.org/r/20180521215449.26423-2-konrad.wilk@oracle.com

---
 arch/x86/kvm/cpuid.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c
index ced851169730..598461e24be3 100644
--- a/arch/x86/kvm/cpuid.c
+++ b/arch/x86/kvm/cpuid.c
@@ -407,8 +407,8 @@ 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 =
-		F(AVX512_4VNNIW) | F(AVX512_4FMAPS) | F(SPEC_CTRL) | F(SSBD) |
-		F(ARCH_CAPABILITIES);
+		F(AVX512_4VNNIW) | F(AVX512_4FMAPS) | F(SPEC_CTRL) |
+		F(SPEC_CTRL_SSBD) | F(ARCH_CAPABILITIES);
 
 	/* all calls to cpuid_count() should be made on the same cpu */
 	get_cpu();

Re: [PATCH] KVM: VMX: Expose SSBD properly to guests.

[Thomas Voegtle]

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On Wed, 23 May 2018, Ben Hutchings wrote:

> On Mon, 2018-05-21 at 17:54 -0400, Konrad Rzeszutek Wilk wrote:
>> The X86_FEATURE_SSBD is an synthetic CPU feature - that is
>> it bit location has no relevance to the real CPUID 0x7.EBX[31]
>> bit position. For that we need the new CPU feature name.
>>
>> Fixes: 52817587e706 ("x86/cpufeatures: Disentangle SSBD enumeration")
>>
>> CC: Paolo Bonzini <pbonzini@redhat.com>
>> Cc: "Radim Krčmář" <rkrcmar@redhat.com>
>> Cc: Thomas Gleixner <tglx@linutronix.de>
>> Cc: Ingo Molnar <mingo@redhat.com>
>> Cc: "H. Peter Anvin" <hpa@zytor.com>
>> Cc: stable@vger.kernel.org
>> Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
>> ---
>>  arch/x86/kvm/cpuid.c | 4 ++--
>>  1 file changed, 2 insertions(+), 2 deletions(-)
>>
>> diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c
>> index ced851169730..598461e24be3 100644
>> --- a/arch/x86/kvm/cpuid.c
>> +++ b/arch/x86/kvm/cpuid.c
>> @@ -407,8 +407,8 @@ 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 =
>> -		F(AVX512_4VNNIW) | F(AVX512_4FMAPS) | F(SPEC_CTRL) | F(SSBD) |
>> -		F(ARCH_CAPABILITIES);
>> +		F(AVX512_4VNNIW) | F(AVX512_4FMAPS) | F(SPEC_CTRL) |
>> +		F(SPEC_CTRL_SSBD) | F(ARCH_CAPABILITIES);
>>
>>  	/* all calls to cpuid_count() should be made on the same cpu */
>>  	get_cpu();
>
> For 4.9-stable, guest_cpuid_has_spec_ctrl() needs a similar fix.
>
> Ben.

Do you mean something like this?

--- a/arch/x86/kvm/cpuid.h
+++ b/arch/x86/kvm/cpuid.h
@@ -179,7 +179,7 @@ static inline bool guest_cpuid_has_spec_ctrl(struct 
kvm_vcpu *vcpu)
         if (best && (best->ebx & bit(X86_FEATURE_AMD_IBRS)))
                 return true;
         best = kvm_find_cpuid_entry(vcpu, 7, 0);
-       return best && (best->edx & (bit(X86_FEATURE_SPEC_CTRL) | 
bit(X86_FEATURE_SSBD)));
+       return best && (best->edx & (bit(X86_FEATURE_SPEC_CTRL) | 
bit(X86_FEATURE_SPEC_CTRL_SSBD)));
  }

  static inline bool guest_cpuid_has_arch_capabilities(struct kvm_vcpu 
*vcpu)