From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from [140.186.70.92] (port=56684 helo=eggs.gnu.org) by lists.gnu.org with esmtp (Exim 4.43) id 1OgdzL-0006hV-7w for qemu-devel@nongnu.org; Wed, 04 Aug 2010 09:26:32 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.69) (envelope-from ) id 1OgdzJ-0005Zj-EG for qemu-devel@nongnu.org; Wed, 04 Aug 2010 09:26:31 -0400 Received: from mx1.redhat.com ([209.132.183.28]:60932) by eggs.gnu.org with esmtp (Exim 4.69) (envelope-from ) id 1OgdzJ-0005ZS-6H for qemu-devel@nongnu.org; Wed, 04 Aug 2010 09:26:29 -0400 Date: Wed, 4 Aug 2010 16:26:25 +0300 From: Gleb Natapov Subject: Re: [Qemu-devel] Anyone seeing huge slowdown launching qemu with Linux 2.6.35? Message-ID: <20100804132625.GN10499@redhat.com> References: <4C586AB9.5040302@codemonkey.ws> <4C586CF9.7030206@redhat.com> <4C588804.5060803@redhat.com> <4C590046.2020705@redhat.com> <4C591D48.9080301@redhat.com> <4C592218.3000901@redhat.com> <4C596549.1070109@codemonkey.ws> <20100804130709.GL10499@redhat.com> <4C5967D8.7080707@codemonkey.ws> <20100804132408.GG28523@amd.home.annexia.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20100804132408.GG28523@amd.home.annexia.org> List-Id: qemu-devel.nongnu.org List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: "Richard W.M. Jones" Cc: qemu-devel@nongnu.org, kvm@vger.kernel.org, Avi Kivity , Gerd Hoffmann On Wed, Aug 04, 2010 at 02:24:08PM +0100, Richard W.M. Jones wrote: > On Wed, Aug 04, 2010 at 08:15:04AM -0500, Anthony Liguori wrote: > > On 08/04/2010 08:07 AM, Gleb Natapov wrote: > > >On Wed, Aug 04, 2010 at 08:04:09AM -0500, Anthony Liguori wrote: > > >>On 08/04/2010 03:17 AM, Avi Kivity wrote: > > >>>For playing games, there are three options: > > >>>- existing fwcfg > > >>>- fwcfg+dma > > >>>- put roms in 4GB-2MB (or whatever we decide the flash size is) > > >>>and have the BIOS copy them > > >>> > > >>>Existing fwcfg is the least amount of work and probably > > >>>satisfactory for isapc. fwcfg+dma is IMO going off a tangent. > > >>>High memory flash is the most hardware-like solution, pretty easy > > >>>from a qemu point of view but requires more work. > > >> > > >>The only trouble I see is that high memory isn't always available. > > >>If it's a 32-bit PC and you've exhausted RAM space, then you're only > > >>left with the PCI hole and it's not clear to me if you can really > > >>pull out 100mb of space there as an option ROM without breaking > > >>something. > > >> > > >We can map it on demand. Guest tells qemu to map rom "A" to address X by > > >writing into some io port. Guest copies rom. Guest tells qemu to unmap > > >it. Better then DMA interface IMHO. > > > > That's what I thought too, but in a 32-bit guest using ~3.5GB of > > RAM, where can you safely get 100MB of memory to full map the ROM? > > If you're going to map chunks at a time, you are basically doing > > DMA. > > It's boot time, so you can just map it over some existing RAM surely? Not with current qemu. This is broken now. > Linuxboot.bin can work out where to map it so it won't be in any > memory either being used or the target for the copy. > -- Gleb.