From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail144.messagelabs.com (mail144.messagelabs.com [216.82.254.51]) by kanga.kvack.org (Postfix) with ESMTP id 061926B0078 for ; Tue, 19 Jan 2010 12:06:53 -0500 (EST) Message-ID: <4B55E5D8.1070402@zytor.com> Date: Tue, 19 Jan 2010 09:03:20 -0800 From: "H. Peter Anvin" MIME-Version: 1.0 Subject: Re: [PATCH v3 04/12] Add "handle page fault" PV helper. References: <1262700774-1808-1-git-send-email-gleb@redhat.com> <1262700774-1808-5-git-send-email-gleb@redhat.com> <1263490267.4244.340.camel@laptop> <20100117144411.GI31692@redhat.com> <4B541D08.9040802@zytor.com> <20100118085022.GA30698@redhat.com> <4B5510B1.9010202@zytor.com> <20100119065537.GF14345@redhat.com> In-Reply-To: <20100119065537.GF14345@redhat.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org To: Gleb Natapov Cc: Peter Zijlstra , kvm@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, avi@redhat.com, mingo@elte.hu, tglx@linutronix.de, riel@redhat.com, cl@linux-foundation.org List-ID: On 01/18/2010 10:55 PM, Gleb Natapov wrote: >> >> What I mean is that vector 14 is page faults -- that's what it is all >> about. Why on Earth do you need another vector? >> > Because this is not usual pagefault that tell the OS that page is not > mapped. This is a notification to a guest OS that the page it is trying > to access is swapped out by the host OS. There is nothing guest can do > about it except schedule another task. So the guest should handle both > type of exceptions: usual #PF when page is not mapped by the guest and > new type of notifications. Ideally we would use one of unused exception > vectors for new type of notifications. > Ah, this kind of stuff. We have talked about this in the past, and the right way to do that is to have the guest OS pick a vector our of the standard 0x20-0xff range, and then notify the hypervisor via a hypercall which vector to use. In Linux this means marking it as a system vector. Note that there are real hardware system vectors which will be mutually exclusive with this, e.g. the UV one. -hpa -- H. Peter Anvin, Intel Open Source Technology Center I work for Intel. I don't speak on their behalf. -- 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