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From: | Anthony Liguori |
Subject: | Re: [Qemu-trivial] [Qemu-devel] [PATCH] Remove PCI class code from virtio balloon device |
Date: | Wed, 21 Mar 2012 11:26:50 -0500 |
User-agent: | Mozilla/5.0 (X11; Linux x86_64; rv:10.0.2) Gecko/20120216 Thunderbird/10.0.2 |
On 03/21/2012 11:11 AM, Michael S. Tsirkin wrote:
On Wed, Mar 21, 2012 at 10:14:35AM -0500, Anthony Liguori wrote:On 03/21/2012 10:10 AM, Michael S. Tsirkin wrote:On Wed, Mar 21, 2012 at 09:42:41AM -0500, Anthony Liguori wrote:On 03/21/2012 08:08 AM, Michael S. Tsirkin wrote:On Wed, Mar 21, 2012 at 11:26:15AM +0000, Stefan Hajnoczi wrote:On Tue, Mar 20, 2012 at 09:19:47PM +1100, David Gibson wrote: Looking at hw/pc_piix.c there are QEMUMachine types for each QEMU release. Legacy machine types (e.g. pc_machine_v0_14) have a .compat_props array that can override qdev properties. Perhaps Michael Tsirkin or someone else can comment on how to wire up hw/virtio-pci.c so that the class code can be overridden. Stefanafaik we already let users over-write it for some other pci devices, look there for examples.From hw/pc_piix.c: .name = "pc-0.10", .desc = "Standard PC, qemu 0.10", .init = pc_init_pci_no_kvmclock, .max_cpus = 255, .compat_props = (GlobalProperty[]) { { .driver = "virtio-blk-pci", .property = "class", .value = stringify(PCI_CLASS_STORAGE_OTHER), },{ And from the earlier part of the thread, yes, it's imperative that we do not change anything in the PCI configuration space for older pc versions regardless of whether it may or may not work. Certain guests (like Windows) use a complex fingerprinting algorithm to determine when hardware changes. It can be hard to detect in simple testing because it's based on a threshold. Regards, Anthony LiguoriWhich reminds me - qemu sticks the release version in guest visible places like CPU version. This is wrong and causes windows guests to print messages about driver updates when you switch. We should find all these places and stop doing this.We could probably get away with doing a query/replace of QEMU_VERSION with qemu_get_version(), make version a static variable that defaults to QEMU_VERSION, and then provide a way for machines to override it. Then pc-0.10 could report a version of 0.10. Regards, Anthony LiguoriFrankly I don't see value in making it visible to the user, at all. We are just triggering windows reactivations without any user benefit. Why not return a fixed value there to avoid that?
I don't see a problem making it fixed for 1.1, but for 1.0 and older, we should expose what we were supposed to expose.
We need to fix the bug first, then we can change the behavior. Regards, Anthony Liguori
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