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 229B6600783 for ; Fri, 22 Jan 2010 02:25:27 -0500 (EST) Date: Fri, 22 Jan 2010 09:25:10 +0200 From: Gleb Natapov Subject: Re: [PATCH v3 04/12] Add "handle page fault" PV helper. Message-ID: <20100122072510.GD2076@redhat.com> References: <20100118085022.GA30698@redhat.com> <4B5510B1.9010202@zytor.com> <20100119065537.GF14345@redhat.com> <4B55E5D8.1070402@zytor.com> <20100119174438.GA19450@redhat.com> <4B5611A9.4050301@zytor.com> <20100120100254.GC5238@redhat.com> <4B5740CD.4020005@zytor.com> <4B58181B.60405@redhat.com> <4B58770A.3050107@zytor.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <4B58770A.3050107@zytor.com> Sender: owner-linux-mm@kvack.org To: "H. Peter Anvin" Cc: Avi Kivity , Peter Zijlstra , kvm@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, mingo@elte.hu, tglx@linutronix.de, riel@redhat.com, cl@linux-foundation.org List-ID: On Thu, Jan 21, 2010 at 07:47:22AM -0800, H. Peter Anvin wrote: > On 01/21/2010 01:02 AM, Avi Kivity wrote: > >> > >> You can also just emulate the state transition -- since you know > >> you're dealing with a flat protected-mode or long-mode OS (and just > >> make that a condition of enabling the feature) you don't have to deal > >> with all the strange combinations of directions that an unrestricted > >> x86 event can take. Since it's an exception, it is unconditional. > > > > Do you mean create the stack frame manually? I'd really like to avoid > > that for many reasons, one of which is performance (need to do all the > > virt-to-phys walks manually), the other is that we're certain to end up > > with something horribly underspecified. I'd really like to keep as > > close as possible to the hardware. For the alternative approach, see Xen. > > > > I obviously didn't mean to do something which didn't look like a > hardware-delivered exception. That by itself provides a tight spec. > The performance issue is real, of course. > > Obviously, the design of VT-x was before my time at Intel, so I'm not > familiar with why the tradeoffs that were done they way they were. > Is it so out of question to reserver exception below 32 for PV use? -- 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