From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from [140.186.70.92] (port=42211 helo=eggs.gnu.org) by lists.gnu.org with esmtp (Exim 4.43) id 1OgdoP-0000PY-IZ for qemu-devel@nongnu.org; Wed, 04 Aug 2010 09:15:18 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.69) (envelope-from ) id 1OgdoK-00039L-AU for qemu-devel@nongnu.org; Wed, 04 Aug 2010 09:15:13 -0400 Received: from mail-qw0-f45.google.com ([209.85.216.45]:64858) by eggs.gnu.org with esmtp (Exim 4.69) (envelope-from ) id 1OgdoK-000398-36 for qemu-devel@nongnu.org; Wed, 04 Aug 2010 09:15:08 -0400 Received: by qwf6 with SMTP id 6so915599qwf.4 for ; Wed, 04 Aug 2010 06:15:07 -0700 (PDT) Message-ID: <4C5967D8.7080707@codemonkey.ws> Date: Wed, 04 Aug 2010 08:15:04 -0500 From: Anthony Liguori MIME-Version: 1.0 Subject: Re: [Qemu-devel] Anyone seeing huge slowdown launching qemu with Linux 2.6.35? References: <4C585F5B.5070502@codemonkey.ws> <4C58635B.7020407@redhat.com> <20100803190525.GB16570@redhat.com> <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> In-Reply-To: <20100804130709.GL10499@redhat.com> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit List-Id: qemu-devel.nongnu.org List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Gleb Natapov Cc: qemu-devel@nongnu.org, "Richard W.M. Jones" , Avi Kivity , kvm@vger.kernel.org, Gerd Hoffmann 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. And what's the upper limit on ROM size that we impose? 100MB is already at the ridiculously large size. Regards, Anthony Liguori > -- > Gleb. >