From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([208.118.235.92]:35703) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1TRSgt-0006SM-7p for qemu-devel@nongnu.org; Thu, 25 Oct 2012 15:02:07 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1TRSgq-0000Ew-W7 for qemu-devel@nongnu.org; Thu, 25 Oct 2012 15:02:02 -0400 Received: from goliath.siemens.de ([192.35.17.28]:18137) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1TRSgq-0000Em-9m for qemu-devel@nongnu.org; Thu, 25 Oct 2012 15:02:00 -0400 Message-ID: <50898C39.8080201@siemens.com> Date: Thu, 25 Oct 2012 21:00:09 +0200 From: Jan Kiszka MIME-Version: 1.0 References: <1350897839-29593-1-git-send-email-pingfank@linux.vnet.ibm.com> <508971E2.9050309@redhat.com> <20121025181311.GA9988@amt.cnet> In-Reply-To: <20121025181311.GA9988@amt.cnet> Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Subject: Re: [Qemu-devel] [patch v4 00/16] push mmio dispatch out of big lock List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Marcelo Tosatti Cc: Peter Maydell , Liu Ping Fan , Stefan Hajnoczi , "qemu-devel@nongnu.org" , Avi Kivity , Anthony Liguori , Paolo Bonzini On 2012-10-25 20:13, Marcelo Tosatti wrote: > On Thu, Oct 25, 2012 at 06:13:51PM +0100, Peter Maydell wrote: >> On 25 October 2012 18:07, Avi Kivity wrote: >>> On 10/25/2012 04:04 PM, Peter Maydell wrote: >>>> Is there a clear up to date description somewhere of the design and >>>> locking strategy here somewhere? I'd rather not have to try to >>>> reconstitute it by reading the whole patchset... >>> >>> It was described somewhere in a document by Marcelo and myself. >>> Basically the goal is to arrive at >>> >>> address_space_write(): >>> rcu_read_lock() >>> mr = lookup() >>> mr->ref() >>> rcu_read_unlock() >>> >>> mr->dispatch() >>> >>> mr->unref() >>> >>> This is the same strategy used in many places in the kernel. >> >> Yes, but this is rather short on the details (eg, does every >> device have its own lock, what are we doing with irqs, how about >> dma from devices, etc etc). It's the details of the design I'd >> like to see described... >> >> -- PMM > > A document should be maintained and updated to reflect ongoing > agreement of problems and solutions... Jan/Liu, someone steps up > to do that? I can pick this up as I have to anyway. First results will be pushed to the wiki, around or after the KVM forum. Jan > > The original is: > http://lists.gnu.org/archive/html/qemu-devel/2012-06/msg04315.html > > For one thing, inter-device DMA issue discussed on the list is not > covered and probably large parts of it are obsolete by now (and > should be deleted). -- Siemens AG, Corporate Technology, CT RTC ITP SDP-DE Corporate Competence Center Embedded Linux