Re: [PATCH RFC v8 10/56] x86/cpufeatures: Add SEV-SNP CPU feature

["Kalra, Ashish" <ashish.kalra@amd.com>]

On 2/21/2023 3:21 PM, Sathyanarayanan Kuppuswamy wrote:
> 
> 
> On 2/20/23 10:38 AM, Michael Roth wrote:
>> From: Brijesh Singh <brijesh.singh@amd.com>
>>
>> Add CPU feature detection for Secure Encrypted Virtualization with
>> Secure Nested Paging. This feature adds a strong memory integrity
>> protection to help prevent malicious hypervisor-based attacks like
>> data replay, memory re-mapping, and more.
>>
>> Signed-off-by: Brijesh Singh <brijesh.singh@amd.com>
>> Signed-off-by: Jarkko Sakkinen <jarkko@profian.com>
>> Signed-off-by: Ashish Kalra <Ashish.Kalra@amd.com>
> 
> Too many signed-off-by's. Are you missing Co-developed-by?
> 
>> Signed-off-by: Michael Roth <michael.roth@amd.com>
>> ---
>>   arch/x86/include/asm/cpufeatures.h       | 1 +
>>   arch/x86/kernel/cpu/amd.c                | 5 +++--
>>   tools/arch/x86/include/asm/cpufeatures.h | 1 +
>>   3 files changed, 5 insertions(+), 2 deletions(-)
>>
>> diff --git a/arch/x86/include/asm/cpufeatures.h b/arch/x86/include/asm/cpufeatures.h
>> index 1419c4e04d45..480b4eaef310 100644
>> --- a/arch/x86/include/asm/cpufeatures.h
>> +++ b/arch/x86/include/asm/cpufeatures.h
>> @@ -420,6 +420,7 @@
>>   #define X86_FEATURE_SEV			(19*32+ 1) /* AMD Secure Encrypted Virtualization */
>>   #define X86_FEATURE_VM_PAGE_FLUSH	(19*32+ 2) /* "" VM Page Flush MSR is supported */
>>   #define X86_FEATURE_SEV_ES		(19*32+ 3) /* AMD Secure Encrypted Virtualization - Encrypted State */
>> +#define X86_FEATURE_SEV_SNP		(19*32+ 4) /* AMD Secure Encrypted Virtualization - Secure Nested Paging */
>>   #define X86_FEATURE_V_TSC_AUX		(19*32+ 9) /* "" Virtual TSC_AUX */
>>   #define X86_FEATURE_SME_COHERENT	(19*32+10) /* "" AMD hardware-enforced cache coherency */
>>   
>> diff --git a/arch/x86/kernel/cpu/amd.c b/arch/x86/kernel/cpu/amd.c
>> index 860b60273df3..c7884198ad5b 100644
>> --- a/arch/x86/kernel/cpu/amd.c
>> +++ b/arch/x86/kernel/cpu/amd.c
>> @@ -558,8 +558,8 @@ static void early_detect_mem_encrypt(struct cpuinfo_x86 *c)
>>   	 *	      SME feature (set in scattered.c).
>>   	 *	      If the kernel has not enabled SME via any means then
>>   	 *	      don't advertise the SME feature.
>> -	 *   For SEV: If BIOS has not enabled SEV then don't advertise the
>> -	 *            SEV and SEV_ES feature (set in scattered.c).
> 
> Did you remove the related scattered.c code mentioned above in a different patch?
>

That is part of the following commit:

commit fb35d30fe5b06cc24444f0405da8fbe0be5330d1
Author: Sean Christopherson <seanjc@google.com>
Date:   Fri Jan 22 12:40:46 2021 -0800

     x86/cpufeatures: Assign dedicated feature word for 
CPUID_0x8000001F[EAX]

     Collect the scattered SME/SEV related feature flags into a dedicated
     word.  There are now five recognized features in CPUID.0x8000001F.EAX,
     with at least one more on the horizon (SEV-SNP).  Using a dedicated 
word
     allows KVM to use its automagic CPUID adjustment logic when reporting
     the set of supported features to userspace.

     No functional change intended.

     Signed-off-by: Sean Christopherson <seanjc@google.com>
     Signed-off-by: Borislav Petkov <bp@suse.de>
     Reviewed-by: Brijesh Singh <brijesh.singh@amd.com>
     Link: 
https://lkml.kernel.org/r/20210122204047.2860075-2-seanjc@google.com

Thanks,
Ashish

>> +	 *   For SEV: If BIOS has not enabled SEV then don't advertise SEV and
>> +	 *	      any additional functionality based on it.
>>   	 *
>>   	 *   In all cases, since support for SME and SEV requires long mode,
>>   	 *   don't advertise the feature under CONFIG_X86_32.
>> @@ -594,6 +594,7 @@ static void early_detect_mem_encrypt(struct cpuinfo_x86 *c)
>>   clear_sev:
>>   		setup_clear_cpu_cap(X86_FEATURE_SEV);
>>   		setup_clear_cpu_cap(X86_FEATURE_SEV_ES);
>> +		setup_clear_cpu_cap(X86_FEATURE_SEV_SNP);
>>   	}
>>   }
>>   
>> diff --git a/tools/arch/x86/include/asm/cpufeatures.h b/tools/arch/x86/include/asm/cpufeatures.h
>> index b71f4f2ecdd5..e81606fcd2ab 100644
>> --- a/tools/arch/x86/include/asm/cpufeatures.h
>> +++ b/tools/arch/x86/include/asm/cpufeatures.h
>> @@ -417,6 +417,7 @@
>>   #define X86_FEATURE_SEV			(19*32+ 1) /* AMD Secure Encrypted Virtualization */
>>   #define X86_FEATURE_VM_PAGE_FLUSH	(19*32+ 2) /* "" VM Page Flush MSR is supported */
>>   #define X86_FEATURE_SEV_ES		(19*32+ 3) /* AMD Secure Encrypted Virtualization - Encrypted State */
>> +#define X86_FEATURE_SEV_SNP		(19*32+ 4) /* AMD Secure Encrypted Virtualization - Secure Nested Paging */
>>   #define X86_FEATURE_V_TSC_AUX		(19*32+ 9) /* "" Virtual TSC_AUX */
>>   #define X86_FEATURE_SME_COHERENT	(19*32+10) /* "" AMD hardware-enforced cache coherency */
>>   
>