linux-kernel - Re: [PATCH 2/2] KVM: x86: VMX: untangle VMXON revision

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Message-ID: <8736amg3q5.fsf@vitty.brq.redhat.com>
Date:   Thu, 05 Mar 2020 17:34:42 +0100
From:   Vitaly Kuznetsov <vkuznets@...hat.com>
To:     Sean Christopherson <sean.j.christopherson@...el.com>
Cc:     Paolo Bonzini <pbonzini@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/2] KVM: x86: VMX: untangle VMXON revision_id setting when using eVMCS

Sean Christopherson <sean.j.christopherson@...el.com> writes:

> On Thu, Mar 05, 2020 at 11:01:23AM +0100, Vitaly Kuznetsov wrote:
>> As stated in alloc_vmxon_regions(), VMXON region needs to be tagged with
>> revision id from MSR_IA32_VMX_BASIC even in case of eVMCS. The logic to
>> do so is not very straightforward: first, we set
>> hdr.revision_id = KVM_EVMCS_VERSION in alloc_vmcs_cpu() just to reset it
>> back to vmcs_config.revision_id in alloc_vmxon_regions(). Simplify this by
>> introducing 'enum vmx_area_type' parameter to what is now known as
>> alloc_vmx_area_cpu().
>
> I'd strongly prefer to keep the alloc_vmcs_cpu() name and call the new enum
> "vmcs_type".  The discrepancy could be resolved by a comment above the
> VMXON_REGION usage, e.g.
>
> 		/* The VMXON region is really just a special type of VMCS. */
> 		vmcs = alloc_vmcs_cpu(VMXON_REGION, cpu, GFP_KERNEL);

I have no strong opinion (but honestly I don't really know what VMXON
region is being used for), Paolo already said 'queued' but I think I'll
send v2 with the suggested changes (including patch prefixes :-)

-- 
Vitaly