Re: [PATCH] KVM: vmx: add mismatched size in vmcs_check32

[Haiwei Li]

On Fri, Apr 9, 2021 at 12:05 AM Sean Christopherson <seanjc@xxxxxxxxxx> wrote:
>
> On Thu, Apr 08, 2021, lihaiwei.kernel@xxxxxxxxx wrote:
> > From: Haiwei Li <lihaiwei@xxxxxxxxxxx>
> >
> > vmcs_check32 misses the check for 64-bit and 64-bit high.
>
> Can you clarify in the changelog that, while it is architecturally legal to
> access 64-bit and 64-bit high fields with a 32-bit read/write in 32-bit mode,
> KVM should never do partial accesses to VMCS fields.  And/or note that the
> 32-bit accesses are done in vmcs_{read,write}64() when necessary?  Hmm, maybe:
>
>   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.

Good suggestion, thanks. I will send v2.