From mboxrd@z Thu Jan 1 00:00:00 1970 From: Arnd Bergmann Subject: Re: [RFC] virtio-blk PCI backend Date: Tue, 20 Nov 2007 11:17:16 +0100 Message-ID: <200711201117.17900.arnd@arndb.de> References: <11944902733951-git-send-email-aliguori@us.ibm.com> <200711200939.19410.borntraeger@de.ibm.com> <4742B053.8080301@qumranet.com> Mime-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Cc: Christian Borntraeger , Avi Kivity To: kvm-devel-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f@public.gmane.org Return-path: In-Reply-To: <4742B053.8080301-atKUWr5tajBWk0Htik3J/w@public.gmane.org> Content-Disposition: inline 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 On Tuesday 20 November 2007, Avi Kivity wrote: > = > > > > Sorry for being late in this thread. > > We (s390) will need a hypercall as we do not have port I/O. I think it = should be > > possible to default to hypercall on s390 and use pio everywhere else. > > =A0 = > = > Or be generic: advertise the methods available according to host = > (kvm/x86, qemu/x86, kvm/s390) and let the guest pick. Not sure if I'm following the reasoning here. Shouldn't the method be inherent to the virtio bus driver? When you use a PCI based virtio bus, the natural choice would be PIO in some way, but you could also have a different virtio implementation on PCI that uses hcalls. This choice is completely up to virtio-pci. On s390, you have a different virtio backend altogether, so you always use DIAG or hcall instead of whatever virtio-pci does. The virtio-blk and other high-level drivers don't need to care about what transport the bus uses in the first place. Arnd <>< ------------------------------------------------------------------------- This SF.net email is sponsored by: Microsoft Defy all challenges. Microsoft(R) Visual Studio 2005. http://clk.atdmt.com/MRT/go/vse0120000070mrt/direct/01/