From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail202.messagelabs.com (mail202.messagelabs.com [216.82.254.227]) by kanga.kvack.org (Postfix) with SMTP id 6F1DB6007E9 for ; Mon, 23 Aug 2010 11:29:27 -0400 (EDT) Date: Mon, 23 Aug 2010 18:29:17 +0300 From: Gleb Natapov Subject: Re: [PATCH v5 02/12] Add PV MSR to enable asynchronous page faults delivery. Message-ID: <20100823152917.GT10499@redhat.com> References: <1279553462-7036-1-git-send-email-gleb@redhat.com> <1279553462-7036-3-git-send-email-gleb@redhat.com> <4C72921A.8000308@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <4C72921A.8000308@redhat.com> Sender: owner-linux-mm@kvack.org To: Avi Kivity Cc: kvm@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, mingo@elte.hu, a.p.zijlstra@chello.nl, tglx@linutronix.de, hpa@zytor.com, riel@redhat.com, cl@linux-foundation.org, mtosatti@redhat.com List-ID: On Mon, Aug 23, 2010 at 06:22:02PM +0300, Avi Kivity wrote: > On 07/19/2010 06:30 PM, Gleb Natapov wrote: > >Guess enables async PF vcpu functionality using this MSR. > > > > > > > >+static int kvm_pv_enable_async_pf(struct kvm_vcpu *vcpu, u64 data) > >+{ > >+ u64 gpa = data& ~0x3f; > >+ int offset = offset_in_page(gpa); > >+ unsigned long addr; > >+ > >+ /* Bits 1:5 are resrved, Should be zero */ > >+ if (data& 0x3e) > >+ return 1; > >+ > >+ vcpu->arch.apf_msr_val = data; > >+ > >+ if (!(data& KVM_ASYNC_PF_ENABLED)) { > >+ vcpu->arch.apf_data = NULL; > >+ return 0; > >+ } > >+ > >+ addr = gfn_to_hva(vcpu->kvm, gpa>> PAGE_SHIFT); > >+ if (kvm_is_error_hva(addr)) > >+ return 1; > >+ > >+ vcpu->arch.apf_data = (u32 __user*)(addr + offset); > > This can be invalidated by host userspace playing with memory > regions. It needs to be recalculated on memory map changes, and it > may disappear from under the guest's feet (in which case we're > allowed to KVM_REQ_TRIPLE_FAULT it). > > (note: this is a much better approach than kvmclock's and vapic's, > we should copy it there) > apf_put_user() tracks memory slot changes and revalidate the address if needed. > >+ > >+ /* check if address is mapped */ > >+ if (get_user(offset, vcpu->arch.apf_data)) { > >+ vcpu->arch.apf_data = NULL; > >+ return 1; > >+ } > > So, this check can succeed today but fail tomorrow. > > >+ return 0; > >+} > >+ > > -- > error compiling committee.c: too many arguments to function -- Gleb. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org