linux-kernel - Re: [PATCH] KVM: vmx: add mismatched size in vmcs

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Message-ID: <c24c9d96-37c5-cfb4-8b84-cb3f8daee500@redhat.com>
Date:   Thu, 8 Apr 2021 18:28:45 +0200
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     Sean Christopherson <seanjc@...gle.com>, lihaiwei.kernel@...il.com
Cc:     linux-kernel@...r.kernel.org, kvm@...r.kernel.org,
        vkuznets@...hat.com, wanpengli@...cent.com, jmattson@...gle.com,
        joro@...tes.org, Haiwei Li <lihaiwei@...cent.com>
Subject: Re: [PATCH] KVM: vmx: add mismatched size in vmcs_check32

On 08/04/21 18:05, Sean Christopherson wrote:
>    Add compile-time assertions in vmcs_check32() to disallow accesses to
>    64-bit and 64-bit high fields via vmcs_{read,write}32().  Upper level
>    KVM code should never do partial accesses to VMCS fields.  KVM handles
>    the split accesses automatically in vmcs_{read,write}64() when running
>    as a 32-bit kernel.

KVM also uses raw vmread/vmwrite (__vmcs_readl/__vmcs_writel) when 
copying to and from the shadow VMCS, so that path will not go through 
vmcs_check32 either.

Paolo