Sean Christopherson <sean.j.christopherson@xxxxxxxxx> wrote: > On Thu, Feb 06, 2020 at 11:47:02AM +0100, Vitaly Kuznetsov wrote: >> linmiaohe <linmiaohe@xxxxxxxxxx> writes: >> >> > From: Miaohe Lin <linmiaohe@xxxxxxxxxx> >> > >> > There is already an smp_mb() barrier in kvm_make_request(). We reuse >> > it here. >> > + /* >> > + * Make sure pending_events is visible before sending >> > + * the request. >> > + * There is already an smp_wmb() in kvm_make_request(), >> > + * we reuse that barrier here. >> > + */ >> >> Let me suggest an alternative wording, >> >> "kvm_make_request() provides smp_wmb() so pending_events changes are >> guaranteed to be visible" >> >> But there is nothing wrong with yours, it's just longer than it could >> be >> :-) Thanks for your alternative wording. It looks much better. >I usually lean in favor of more comments, but in thise case I'd vote to drop the comment altogether. There are lots of places that rely on the >smp_wmb() in kvm_make_request() without a comment, e.g. the cases for APIC_DM_STARTUP and APIC_DM_REMRD in this same switch, kvm_inject_nmi(), etc... One might wonder what makes INIT special. > >And on the flip side, APIC_DM_STARTUP is a good example of when a >smp_wmb()/smp_rmb() is needed and commented correctly (though calling out the exactly location of the other half would be helpful). Yeh, I think the comment should be dropped too. :) Thanks to both for review! I would send v2.
