Re: [PATCH] KVM: Remove redundant smp_mb() in the kvm_mmu_commit_zap_page()

[Xiao Guangrong]

On 03/04/2016 04:04 PM, Paolo Bonzini wrote:
> On 04/03/2016 02:35, Lan Tianyu wrote:
> > The following kvm_flush_remote_tlbs() will call smp_mb() inside and so
> > remove smp_mb() here.
> >
> > Signed-off-by: Lan Tianyu <tianyu.lan@xxxxxxxxx>
> > ---
> >   arch/x86/kvm/mmu.c | 6 ------
> >   1 file changed, 6 deletions(-)
> >
> > diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
> > index a54ecd9..6315416 100644
> > --- a/arch/x86/kvm/mmu.c
> > +++ b/arch/x86/kvm/mmu.c
> > @@ -2383,12 +2383,6 @@ static void kvm_mmu_commit_zap_page(struct kvm *kvm,
> >   		return;
> >
> >   	/*
> > -	 * wmb: make sure everyone sees our modifications to the page tables
> > -	 * rmb: make sure we see changes to vcpu->mode
> > -	 */
> > -	smp_mb();
> > -
> > -	/*
> >   	 * Wait for all vcpus to exit guest mode and/or lockless shadow
> >   	 * page table walks.
> >   	 */
>
> kvm_flush_remote_tlbs loads kvm->tlbs_dirty before issuing the memory
> barrier.  I think it's okay if the load is done earlier, but I'd like
> Guangrong to take a look.

Yes, It looks good to me, but please keep the comment.

Thanks!