From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1760425Ab0JIStP (ORCPT ); Sat, 9 Oct 2010 14:49:15 -0400 Received: from mx1.redhat.com ([209.132.183.28]:19230 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756091Ab0JIStO (ORCPT ); Sat, 9 Oct 2010 14:49:14 -0400 Message-ID: <4CB0B8EF.3050702@redhat.com> Date: Sat, 09 Oct 2010 20:48:15 +0200 From: Avi Kivity User-Agent: Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv:1.9.2.9) Gecko/20100921 Fedora/3.1.4-1.fc13 Thunderbird/3.1.4 MIME-Version: 1.0 To: Gleb Natapov 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 Subject: Re: [PATCH v6 08/12] Handle async PF in a guest. References: <1286207794-16120-1-git-send-email-gleb@redhat.com> <1286207794-16120-9-git-send-email-gleb@redhat.com> <4CADC6C3.3040305@redhat.com> <20101007171418.GA2397@redhat.com> <4CAE00CB.1070400@redhat.com> <20101007180340.GI2397@redhat.com> In-Reply-To: <20101007180340.GI2397@redhat.com> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 10/07/2010 08:03 PM, Gleb Natapov wrote: > > >> > > >Host side keeps track of outstanding apfs and will not send apf for the > > >same phys address twice. It will halt vcpu instead. > > > > What about different pages, running the scheduler code? > > > We can get couple of nested apfs, just like we can get nested > interrupts. Since scheduler disables preemption second apf will halt. How much is a couple? Consider: SIGSTOP Entire process swapped out SIGCONT We can get APF's on the current code, the scheduler code, the stack, any debugging code in between (e.g. ftrace), and the page tables for all of these. -- I have a truly marvellous patch that fixes the bug which this signature is too narrow to contain.