linux-kernel - Re: [RFC 04/16] KVM: selftests: set CPUID before setting sregs in vcpu creation

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Message-ID: <20211013150534.noxfgms66xkwvhxq@amd.com>
Date:   Wed, 13 Oct 2021 10:05:34 -0500
From:   Michael Roth <michael.roth@....com>
To:     Krish Sadhukhan <krish.sadhukhan@...cle.com>
CC:     <linux-kselftest@...r.kernel.org>, <kvm@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>, <x86@...nel.org>,
        Nathan Tempelman <natet@...gle.com>,
        Marc Orr <marcorr@...gle.com>,
        Steve Rutherford <srutherford@...gle.com>,
        Sean Christopherson <seanjc@...gle.com>,
        "Mingwei Zhang" <mizhang@...gle.com>,
        Brijesh Singh <brijesh.singh@....com>,
        "Tom Lendacky" <thomas.lendacky@....com>,
        Varad Gautam <varad.gautam@...e.com>,
        Shuah Khan <shuah@...nel.org>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        "David Woodhouse" <dwmw@...zon.co.uk>,
        Ricardo Koller <ricarkol@...gle.com>,
        "Jim Mattson" <jmattson@...gle.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        "Joerg Roedel" <joro@...tes.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        "H . Peter Anvin" <hpa@...or.com>
Subject: Re: [RFC 04/16] KVM: selftests: set CPUID before setting sregs in
 vcpu creation

On Tue, Oct 12, 2021 at 06:45:09PM -0700, Krish Sadhukhan wrote:
> 
> On 10/6/21 1:36 PM, Michael Roth wrote:
> > KVM_SET_CPUID*, but kselftests currently call KVM_SET_SREGS as part of
> > vm_vcpu_add_default(),*prior*  to vCPU creation, so there's no
> > opportunity to call KVM_SET_CPUID* in advance. As a result,
> In the current code, I see that KVM_SET_SREGS is called by vcpu_setup()
> which is called after vm_vcpu_add() that calls KVM_CREATE_VCPU. Since you
> mentioned "prior", I wanted to check if the wording was wrong or if I missed
> something.

Ah, yes, just poorly worded. What I meant to convey is that from the
perspective the test program the vm_vcpu_add* call that creates the vcpu does
the KVM_SET_SREGS, so there's no way to call KVM_SET_CPUID in advance other
than to have vm_vcpu_add* do it as part of creating the vcpu. I get the
wording fixed up on that.