linux-kernel - Re: [RFC PATCH V5 09/15] x86/hyperv: Add smp support for sev-snp guest

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Date:   Thu, 4 May 2023 08:51:50 -0700
From:   Tianyu Lan <ltykernel@...il.com>
To:     Tom Lendacky <thomas.lendacky@....com>, luto@...nel.org,
        tglx@...utronix.de, mingo@...hat.com, bp@...en8.de,
        dave.hansen@...ux.intel.com, x86@...nel.org, hpa@...or.com,
        seanjc@...gle.com, pbonzini@...hat.com, jgross@...e.com,
        tiala@...rosoft.com, kirill@...temov.name,
        jiangshan.ljs@...group.com, peterz@...radead.org,
        ashish.kalra@....com, srutherford@...gle.com,
        akpm@...ux-foundation.org, anshuman.khandual@....com,
        pawan.kumar.gupta@...ux.intel.com, adrian.hunter@...el.com,
        daniel.sneddon@...ux.intel.com, alexander.shishkin@...ux.intel.com,
        sandipan.das@....com, ray.huang@....com, brijesh.singh@....com,
        michael.roth@....com, venu.busireddy@...cle.com,
        sterritt@...gle.com, tony.luck@...el.com, samitolvanen@...gle.com,
        fenghua.yu@...el.com
Cc:     pangupta@....com, linux-kernel@...r.kernel.org,
        kvm@...r.kernel.org, linux-hyperv@...r.kernel.org,
        linux-arch@...r.kernel.org
Subject: Re: [RFC PATCH V5 09/15] x86/hyperv: Add smp support for sev-snp
 guest

On 5/1/2023 8:46 AM, Tom Lendacky wrote:
>> +    vmsa->sev_features.snp = 1;
>> +    vmsa->sev_features.restrict_injection = 1;
> 
> So this means that any other feature bits set in the BSP won't be set in 
> the AP? Shouldn't you be using the BSP value and checking to be sure 
> what you really want set is set?

So far, the snp flag is enough. You are right that we need to keep it as 
same value on the both BSP and APs. will update in the next version.