From mboxrd@z Thu Jan 1 00:00:00 1970 From: Avi Kivity Subject: Re: [ANNOUNCE] kvm-14 release Date: Thu, 22 Feb 2007 19:29:49 +0200 Message-ID: <45DDD30D.4000809@qumranet.com> References: <45D98390.6060001@qumranet.com> <45DA25D9.1060509@aurel32.net> <45DA9FFA.2020009@qumranet.com> <45DB7514.3040409@aurel32.net> <45DBFD6E.2060507@qumranet.com> <45DC51E3.7010205@aurel32.net> <45DC54B5.9080608@qumranet.com> <45DC5D4E.5000300@bull.net> <45DC65C9.6010104@codemonkey.ws> <45DDC641.3030001@bull.net> <45DDC6F3.8080104@qumranet.com> <45DDD21F.4080202@codemonkey.ws> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Cc: kvm-devel , Laurent Vivier To: Anthony Liguori Return-path: In-Reply-To: <45DDD21F.4080202-rdkfGonbjUSkNkDKm+mE6A@public.gmane.org> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: kvm-devel-bounces-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f@public.gmane.org Errors-To: kvm-devel-bounces-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f@public.gmane.org List-Id: kvm.vger.kernel.org Anthony Liguori wrote: > Avi Kivity wrote: >> Laurent Vivier wrote: >>> There are remaining issues : libposix-aio uses kernel AIO, so files >>> must be >>> opened using O_DIRECT and buffers must be aligned. libposix-aio is >>> able to >>> manage other cases but this has a performance cost. >>> >>> >> >> Because the guest is also doing dma, the buffers are expected to be >> aligned (it might be different if using pio, but unlikely). > > The IDE emulation always uses a temporary buffer. This is partially > because you cannot always rely on being able to use an offset on > phys_ram_base (when doing user only emulation). Why is that? > > We can pretty easily patch this code though to use the DMA address > directly instead of the temporary buffer in the non PIO case. We > still have to define a raw_pread() that is capable of emulating sector > alignment though since Linux will use PIO at first. Sure. It seems worthwhile for mainline qemu too. -- error compiling committee.c: too many arguments to function ------------------------------------------------------------------------- Take Surveys. Earn Cash. Influence the Future of IT Join SourceForge.net's Techsay panel and you'll get the chance to share your opinions on IT & business topics through brief surveys-and earn cash http://www.techsay.com/default.php?page=join.php&p=sourceforge&CID=DEVDEV