From mboxrd@z Thu Jan 1 00:00:00 1970 From: Avi Kivity Subject: Re: [PATCH] Add shared memory PCI device that shares a memory object betweens VMs Date: Thu, 02 Apr 2009 10:07:36 +0300 Message-ID: <49D46438.7040501@redhat.com> References: <1238600608-9120-1-git-send-email-cam@cs.ualberta.ca> <49D3965C.1030503@codemonkey.ws> <49D3AD79.7080708@redhat.com> <49D3B7ED.4030303@codemonkey.ws> <49D3CF4B.7050500@cs.ualberta.ca> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Cc: Anthony Liguori , kvm@vger.kernel.org To: Cam Macdonell Return-path: Received: from mx2.redhat.com ([66.187.237.31]:50425 "EHLO mx2.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751539AbZDBHHB (ORCPT ); Thu, 2 Apr 2009 03:07:01 -0400 In-Reply-To: <49D3CF4B.7050500@cs.ualberta.ca> Sender: kvm-owner@vger.kernel.org List-ID: Cam Macdonell wrote: > I think there is value for static memory sharing. It can be used for > fast, simple synchronization and communication between guests (and the > host) that use need to share data that needs to be updated frequently > (such as a simple cache or notification system). It may not be a > common task, but I think static sharing has its place and that's what > this device is for at this point. It would be good to detail a use case for reference. >> Then you need a side channel to communicate the information to the >> guest. > > Couldn't one of the registers in BAR0 be used to store the actual > (non-power-of-two) size? The PCI config space (where the BARs reside) is a good place for it. Registers 0x40+ are device specific IIRC. -- I have a truly marvellous patch that fixes the bug which this signature is too narrow to contain.