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 ESMTP id CBDB36B006A for ; Tue, 19 Jan 2010 15:13:54 -0500 (EST) Message-ID: <4B5611A9.4050301@zytor.com> Date: Tue, 19 Jan 2010 12:10:17 -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> <4B55E5D8.1070402@zytor.com> <20100119174438.GA19450@redhat.com> In-Reply-To: <20100119174438.GA19450@redhat.com> Content-Type: text/plain; charset=ISO-8859-1 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 01/19/2010 09:44 AM, Gleb Natapov wrote: > > Yes it can be done this way and I'll look into it once more. Using > exception vector is more convenient for three reasons: it allows to pass > additional data in error code, it doesn't require guest to issue EOI, > exception can be injected when interrupts are disabled by a guest. The > last one is not important for now since host doesn't inject notifications > when interrupts are disabled currently. Having Intel allocate one > exception vector for hypervisor use would be really nice though. > That's probably not going to happen, for the rather obvious reason: *you already have 224 of them*. You seem to be thinking here that vectors 0-31 have to be exceptions and 32-255 have to be interrupts. *There is no such distinction*; the only thing special about 0-31 is that we (Intel) reserve the right to control the assignments; for 32-255 the platform and OS control the assignment. You can have the guest OS take an exception on a vector above 31 just fine; you just need it to tell the hypervisor which vector it, the OS, assigned for this purpose. -hpa -- 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