linux-kernel - Re: [PATCH v2 1/2] x86/cpufeatures: Add virtual TSC

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Date:   Wed, 20 Apr 2022 10:02:21 -0500
From:   "Moger, Babu" <babu.moger@....com>
To:     Borislav Petkov <bp@...en8.de>
Cc:     tglx@...utronix.de, mingo@...hat.com, dave.hansen@...ux.intel.com,
        hpa@...or.com, pbonzini@...hat.com, seanjc@...gle.com,
        vkuznets@...hat.com, jmattson@...gle.com, joro@...tes.org,
        wanpengli@...cent.com, linux-kernel@...r.kernel.org,
        kvm@...r.kernel.org, x86@...nel.org
Subject: Re: [PATCH v2 1/2] x86/cpufeatures: Add virtual TSC_AUX feature bit


On 4/20/22 06:43, Borislav Petkov wrote:
> On Tue, Apr 19, 2022 at 03:53:52PM -0500, Babu Moger wrote:
>> The TSC_AUX Virtualization feature allows AMD SEV-ES guests to securely use
>> TSC_AUX (auxiliary time stamp counter data) MSR in RDTSCP and RDPID
>> instructions.
>>
>> The TSC_AUX MSR is typically initialized to APIC ID or another unique
>> identifier so that software can quickly associate returned TSC value
>> with the logical processor.
>>
>> Add the feature bit and also include it in the kvm for detection.
>>
>> Signed-off-by: Babu Moger <babu.moger@....com>
>> Acked-by: Borislav Petkov <bp@...e.de>
>> ---
>> v2:
>> Fixed the text(commented by Boris).
>> Added Acked-by from Boris.
>>
>> v1:
>> https://nam11.safelinks.protection.outlook.com/?url=https%3A%2F%2Flore.kernel.org%2Fkvm%2F164937947020.1047063.14919887750944564032.stgit%40bmoger-ubuntu%2F&amp;data=05%7C01%7Cbabu.moger%40amd.com%7Cf826192970c549ae73af08da22c2ff93%7C3dd8961fe4884e608e11a82d994e183d%7C0%7C0%7C637860518176768607%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C3000%7C%7C%7C&amp;sdata=fExIt5ghvuew%2BXKzGyixye2%2BLQncv91274nt8I0NXbY%3D&amp;reserved=0
>>
>>  arch/x86/include/asm/cpufeatures.h |    1 +
>>  arch/x86/kvm/cpuid.c               |    2 +-
>>  2 files changed, 2 insertions(+), 1 deletion(-)
>>
>> diff --git a/arch/x86/include/asm/cpufeatures.h b/arch/x86/include/asm/cpufeatures.h
>> index 73e643ae94b6..1bc66a17a95a 100644
>> --- a/arch/x86/include/asm/cpufeatures.h
>> +++ b/arch/x86/include/asm/cpufeatures.h
>> @@ -405,6 +405,7 @@
>>  #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_V_TSC_AUX		(19*32+ 9) /* Virtual TSC_AUX */
> I forgot from the last time: nothing is going to use that bit in
> userspace so make that
>
> #define X86_FEATURE_V_TSC_AUX		(19*32+ 9) /* "" Virtual TSC_AUX */

Ok. Sure.

Thanks

>
> please.
>
> Thx.
>
-- 
Thanks
Babu Moger