----- Original Message ----- > From: "Radim Krčmář" <rkrcmar@xxxxxxxxxx> > To: "James Hogan" <james.hogan@xxxxxxxxxx> > Cc: "Paolo Bonzini" <pbonzini@xxxxxxxxxx>, linux-kernel@xxxxxxxxxxxxxxx, kvm@xxxxxxxxxxxxxxx, "Christoffer Dall" > <cdall@xxxxxxxxxx>, "Andrew Jones" <drjones@xxxxxxxxxx>, "Marc Zyngier" <marc.zyngier@xxxxxxx>, "Christian > Borntraeger" <borntraeger@xxxxxxxxxx>, "Cornelia Huck" <cornelia.huck@xxxxxxxxxx>, "Paul Mackerras" > <paulus@xxxxxxxxxx> > Sent: Wednesday, April 12, 2017 3:31:24 AM > Subject: Re: [PATCH RFC 1/6] KVM: fix guest_mode optimization in kvm_make_all_cpus_request() > > 2017-04-11 10:37+0100, James Hogan: > > Hi Paolo, > > > > On Tue, Apr 11, 2017 at 01:25:04PM +0800, Paolo Bonzini wrote: > >> On 07/04/2017 05:02, James Hogan wrote: > >> > This presumably changes the behaviour on x86, from != OUTSIDE_GUEST_MODE > >> > to == IN_GUEST_MODE. so: > >> > - you'll no longer get IPIs if its in READING_SHADOW_PAGE_TABLES (which > >> > MIPS also now uses when accessing mappings outside of guest mode and > >> > depends upon to wait until the old mappings are no longer in use). > >> > >> This is wrong, the purpose of READING_SHADOW_PAGE_TABLES is > >> "kvm_flush_remote_tlbs > >> should send me an IPI, because I want to stop kvm_flush_remote_tlbs until > >> I'm done > >> reading the page tables". > > > > That sounds equivalent to what I meant for MIPS, i.e. > > kvm_flush_remote_tlbs() does the waiting (not the thing accessing guest > > mappings). Yeah, I meant "it's wrong in Radim's patches". Not hard to fix though. Thanks for the review! Paolo > I agree, thanks for noticing this. It would be a huge mistake to drop > the synchronization. >
