linux-kernel - Re: [PATCH V3 5/9] x86/hyperv: Use vmmcall to implement Hyper-V hypercall in sev-snp enlightened guest

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Date:   Fri, 28 Jul 2023 18:45:54 +0800
From:   Tianyu Lan <ltykernel@...il.com>
To:     "Michael Kelley (LINUX)" <mikelley@...rosoft.com>,
        KY Srinivasan <kys@...rosoft.com>,
        Haiyang Zhang <haiyangz@...rosoft.com>,
        "wei.liu@...nel.org" <wei.liu@...nel.org>,
        Dexuan Cui <decui@...rosoft.com>,
        "tglx@...utronix.de" <tglx@...utronix.de>,
        "mingo@...hat.com" <mingo@...hat.com>,
        "bp@...en8.de" <bp@...en8.de>,
        "dave.hansen@...ux.intel.com" <dave.hansen@...ux.intel.com>,
        "x86@...nel.org" <x86@...nel.org>, "hpa@...or.com" <hpa@...or.com>,
        "daniel.lezcano@...aro.org" <daniel.lezcano@...aro.org>,
        "arnd@...db.de" <arnd@...db.de>
Cc:     Tianyu Lan <Tianyu.Lan@...rosoft.com>,
        "linux-arch@...r.kernel.org" <linux-arch@...r.kernel.org>,
        "linux-hyperv@...r.kernel.org" <linux-hyperv@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "vkuznets@...hat.com" <vkuznets@...hat.com>
Subject: Re: [PATCH V3 5/9] x86/hyperv: Use vmmcall to implement Hyper-V
 hypercall in sev-snp enlightened guest

On 7/26/2023 10:29 PM, Michael Kelley (LINUX) wrote:
>> Hi Michael:
>> 	Thanks for your review. The patch mentioned by Boris has not been
>> merged and so still use X86_FEATURE_SEV_ES here. We may replace the
>> feature flag with X86_FEATURE_SEV_SNP after it's upstreamed.
>>
> Just so I'm clear, is it true that in an SEV-SNP VM, the CPUID flags for
> SEV-ES*and*  SEV-SNP are set?  That would seem to be necessary for
> your approach to work.

Yes, SEV and SEV-ES flags are set in the SEV-SNP guest and they are 
necessary.

> 
> I wonder if it would be better to take the patch from Brijesh Singh
> that adds X86_FEATURE_SEV_SNP and add it to your patch set (with
> Brijesh's agreement, of course).  That patch is small and straightforward.
>

I will sync with Brijesh. Thanks for suggestion.