From mboxrd@z Thu Jan 1 00:00:00 1970 From: Avi Kivity Subject: Re: cr3 OOS optimisation breaks 32-bit GNU/kFreeBSD guest Date: Tue, 24 Mar 2009 11:47:33 +0200 Message-ID: <49C8AC35.3030803@redhat.com> References: <20090223003305.GW12976@hall.aurel32.net> <20090320231405.GA26415@amt.cnet> <49C60644.2090904@redhat.com> <20090323172725.GA28775@amt.cnet> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Cc: Aurelien Jarno , kvm@vger.kernel.org To: Marcelo Tosatti Return-path: Received: from mx2.redhat.com ([66.187.237.31]:45018 "EHLO mx2.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757194AbZCXJro (ORCPT ); Tue, 24 Mar 2009 05:47:44 -0400 In-Reply-To: <20090323172725.GA28775@amt.cnet> Sender: kvm-owner@vger.kernel.org List-ID: Marcelo Tosatti wrote: >> Maybe it's best to resync when relinking a global page? >> > > How about this. It will shorten the unsync period of global pages, > unfortunately. > > diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c > index 2a36f7f..bccdcc7 100644 > --- a/arch/x86/kvm/mmu.c > +++ b/arch/x86/kvm/mmu.c > @@ -1238,6 +1238,10 @@ static struct kvm_mmu_page *kvm_mmu_get_page(struct kvm_vcpu *vcpu, > set_bit(KVM_REQ_MMU_SYNC, &vcpu->requests); > kvm_mmu_mark_parents_unsync(vcpu, sp); > } > + if (role.level != PT_PAGE_TABLE_LEVEL && > + !list_empty(&vcpu->kvm->arch.oos_global_pages)) > + set_bit(KVM_REQ_MMU_GLOBAL_SYNC, &vcpu->requests); > + > pgprintk("%s: found\n", __func__); > return sp; > } > diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c > index 2ea8262..48169d7 100644 > --- a/arch/x86/kvm/x86.c > +++ b/arch/x86/kvm/x86.c > @@ -3109,6 +3109,8 @@ static int vcpu_enter_guest(struct kvm_vcpu *vcpu, struct kvm_run *kvm_run) > kvm_write_guest_time(vcpu); > if (test_and_clear_bit(KVM_REQ_MMU_SYNC, &vcpu->requests)) > kvm_mmu_sync_roots(vcpu); > + if (test_and_clear_bit(KVM_REQ_MMU_GLOBAL_SYNC, &vcpu->requests)) > + kvm_mmu_sync_global(vcpu); > if (test_and_clear_bit(KVM_REQ_TLB_FLUSH, &vcpu->requests)) > kvm_x86_ops->tlb_flush(vcpu); > if (test_and_clear_bit(KVM_REQ_REPORT_TPR_ACCESS Windows will (I think) write a PDE on every context switch, so this effectively disables global unsync for that guest. What about recursively syncing the newly linked page in FNAME(fetch)()? If the page isn't global, this becomes a no-op, so no new overhead. The only question is the expense when linking a populated top-level page, especially in long mode. -- Do not meddle in the internals of kernels, for they are subtle and quick to panic.