From mboxrd@z Thu Jan 1 00:00:00 1970 From: Anthony Liguori Subject: Re: [PATCH] Inter-VM shared memory PCI device Date: Tue, 09 Mar 2010 11:34:44 -0600 Message-ID: <4B9686B4.9030202@codemonkey.ws> References: <1267833161-25267-1-git-send-email-cam@cs.ualberta.ca> <1267833161-25267-2-git-send-email-cam@cs.ualberta.ca> <4B94C9B3.1060904@redhat.com> <8286e4ee1003080957v9bb4837x187cebb8477348c2@mail.gmail.com> <4B962301.3030008@redhat.com> <8286e4ee1003090724m1ef0b571g8b705a24e36e1753@mail.gmail.com> <8286e4ee1003090727j1d45e5dq3bc5d2ae89c354c@mail.gmail.com> <4B968521.7000208@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Cc: Cam Macdonell , kvm@vger.kernel.org, qemu-devel@nongnu.org To: Avi Kivity Return-path: Received: from mail-wy0-f174.google.com ([74.125.82.174]:36802 "EHLO mail-wy0-f174.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751113Ab0CIRev (ORCPT ); Tue, 9 Mar 2010 12:34:51 -0500 Received: by wya21 with SMTP id 21so3920220wya.19 for ; Tue, 09 Mar 2010 09:34:50 -0800 (PST) In-Reply-To: <4B968521.7000208@redhat.com> Sender: kvm-owner@vger.kernel.org List-ID: On 03/09/2010 11:28 AM, Avi Kivity wrote: > On 03/09/2010 05:27 PM, Cam Macdonell wrote: >> >>> >>>> Registers are used >>>> for synchronization between guests sharing the same memory object when >>>> interrupts are supported (this requires using the shared memory >>>> server). >>>> >>> How does the driver detect whether interrupts are supported or not? >> At the moment, the VM ID is set to -1 if interrupts aren't supported, >> but that may not be the clearest way to do things. With UIO is there >> a way to detect if the interrupt pin is on? > > I suggest not designing the device to uio. Make it a good > guest-independent device, and if uio doesn't fit it, change it. You can always fall back to reading the config space directly. It's not strictly required that you stick to the UIO interface. > Why not support interrupts unconditionally? Is the device useful > without interrupts? You can always just have interrupts enabled and not use them if that's desired. Regards, Anthony Liguori