linux-kernel - Re: [PATCH v5 04/19] KVM:x86: Refresh CPUID on write to guest MSR_IA32

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Date:   Fri, 4 Aug 2023 23:43:15 +0200
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     Sean Christopherson <seanjc@...gle.com>,
        Yang Weijiang <weijiang.yang@...el.com>
Cc:     peterz@...radead.org, john.allen@....com, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org, rick.p.edgecombe@...el.com,
        chao.gao@...el.com, binbin.wu@...ux.intel.com,
        Zhang Yi Z <yi.z.zhang@...ux.intel.com>
Subject: Re: [PATCH v5 04/19] KVM:x86: Refresh CPUID on write to guest
 MSR_IA32_XSS

On 8/4/23 18:02, Sean Christopherson wrote:
>> Update CPUID(EAX=0DH,ECX=1) when the guest's XSS is modified.
>> CPUID(EAX=0DH,ECX=1).EBX reports required storage size of
>> all enabled xstate features in XCR0 | XSS. Guest can allocate
>> sufficient xsave buffer based on the info.
>
> Please wrap changelogs closer to ~75 chars.  I'm pretty sure this isn't the first
> time I've made this request...

I suspect this is because of the long "word" CPUID(EAX=0DH,ECX=1).EBX. 
It would make the lengths less homogeneous if lines 1 stayed the same 
but lines 2-4 became longer.

Paolo