Re: [PATCH 22/43] KVM: VMX: Remove direct write to vcpu->arch.cr0 during vCPU RESET/INIT

[Reiji Watanabe]

On Fri, Apr 23, 2021 at 5:51 PM Sean Christopherson <seanjc@xxxxxxxxxx> wrote:
>
> Remove a bogus write to vcpu->arch.cr0 that immediately precedes
> vmx_set_cr0() during vCPU RESET/INIT.  For RESET, this is a nop since
> the "old" CR0 value is meaningless.  But for INIT, if the vCPU is coming
> from paging enabled mode, crushing vcpu->arch.cr0 will cause the various
> is_paging() checks in vmx_set_cr0() to get false negatives.
>
> For the exit_lmode() case, the false negative is benign as vmx_set_efer()
> is called immediately after vmx_set_cr0().
>
> For EPT without unrestricted guest, the false negative will cause KVM to
> unnecessarily run with CR3 load/store exiting.  But again, this is
> benign, albeit sub-optimal.
>
> Signed-off-by: Sean Christopherson <seanjc@xxxxxxxxxx>

Reviewed-by: Reiji Watanabe <reijiw@xxxxxxxxxx>