On Sun, 2 Oct 2011 11:09:00 +0200, "Michael S. Tsirkin" <mst@xxxxxxxxxx> wrote: > On Mon, Sep 19, 2011 at 05:19:49PM +0930, Rusty Russell wrote: > > On Mon, 19 Sep 2011 09:01:50 +0300, "Michael S. Tsirkin" <mst@xxxxxxxxxx> wrote: > > > On Mon, Sep 19, 2011 at 01:05:17PM +0930, Rusty Russell wrote: > > > > On Sat, 20 Aug 2011 23:00:44 +0300, "Michael S. Tsirkin" <mst@xxxxxxxxxx> wrote: > > > > > On Fri, Aug 19, 2011 at 07:33:07PM +0300, Sasha Levin wrote: > > > > > > Maybe this is better solved by copying the way it was done in PCI itself > > > > > > with capability linked list? > > > > > > > > > > There are any number of ways to lay out the structure. I went for what > > > > > seemed a simplest one. For MSI-X the train has left the station. We > > > > > can probably still tweak where the high 32 bit features > > > > > for 64 bit features are. No idea if it's worth it. > > > > > > > > Sorry, this has been in the back of my mind. I think it's a good idea; > > > > can we use the capability linked list for pre-device specific stuff from > > > > now on? > > > > > > > > Thanks, > > > > Rusty. > > > > > > Do we even want capability bits then? > > > We can give each capability an ack flag ... > > > > We could have, and if I'd known PCI when I designed virtio I might have. > > > > But it's not easy now to map structure offsets to that scheme, and we > > can't really force such a change on the non-PCI users. So I'd say we > > should only do it for the non-device-specific options. ie. we'll still > > have the MSI-X case move the device-specific config, but we'll use a > > linked list from now on, eg. for the next 32 features bits... > > > > Thoughts? > > Rusty. > > So I thought about this some more. It probably makes sense to > stop adding info in the io space, and start adding new stuff in > memory space which is much less contrained. > > As we need to keep compatibility, and also because memory access is > much slower with kvm so we prefer io for datapath, we could have the > first X bytes still mirrored in io space. > > MSIX is there, and it's pointed to from config space, > so we could just put our stuff at offset 0. > > Or if we wanted a lot of flexibility, we could add pointers, in config > space, to device specific and non device specific regions in memory > space. > > Makes sense? I've cc'd David Gibson who has noted in the past that I/O space on PPC is icky. I think a linked list for future virtio-pci extensions makes sense (not device-specific stuff, that's great as a simple structure). I think mirroring everything in mem space makes sense, too. Thanks, Rusty. -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
