On Tue, Apr 11, 2023 at 05:07:11PM +0800, Jason Wang wrote: > On Tue, Apr 11, 2023 at 3:00 PM Michael S. Tsirkin <m...@redhat.com> wrote: > > > > On Tue, Apr 11, 2023 at 10:19:39AM +0800, Jason Wang wrote: > > > On Mon, Apr 10, 2023 at 6:04 PM Michael S. Tsirkin <m...@redhat.com> > > > wrote: > > > > > > > > On Mon, Apr 10, 2023 at 03:16:46PM +0800, Jason Wang wrote: > > > > > On Mon, Apr 10, 2023 at 2:24 PM Michael S. Tsirkin <m...@redhat.com> > > > > > wrote: > > > > > > > > > > > > On Mon, Apr 10, 2023 at 09:36:17AM +0800, Jason Wang wrote: > > > > > > > On Fri, Mar 31, 2023 at 7:00 AM Parav Pandit <pa...@nvidia.com> > > > > > > > wrote: > > > > > > > > > > > > > > > > PCI device configuration space for capabilities is limited to > > > > > > > > only 192 > > > > > > > > bytes shared by many PCI capabilities of generic PCI device and > > > > > > > > virtio > > > > > > > > specific. > > > > > > > > > > > > > > > > Hence, introduce virtio extended capability that uses PCI > > > > > > > > Express > > > > > > > > extended capability. > > > > > > > > Subsequent patch uses this virtio extended capability. > > > > > > > > > > > > > > > > Co-developed-by: Satananda Burla <sbu...@marvell.com> > > > > > > > > Signed-off-by: Parav Pandit <pa...@nvidia.com> > > > > > > > > > > > > > > Can you explain the differences compared to what I've used to > > > > > > > propose? > > > > > > > > > > > > > > https://www.mail-archive.com/virtio-dev@lists.oasis-open.org/msg08078.html > > > > > > > > > > > > > > This can save time for everybody. > > > > > > > > > > > > > > Thanks > > > > > > > > > > > > BTW another advantage of extended capabilities is - these are > > > > > > actually > > > > > > cheaper to access from a VM than classic config space. > > > > > > > > > > Config space/BAR is allowed by both of the proposals or anything I > > > > > missed? > > > > > > > > > > > > > > > > > > > > > > > Several points > > > > > > - I don't like it that yours is 32 bit. We do not need 2 variants > > > > > > just > > > > > > make it all 64 bit > > > > > > > > > > That's fine. > > > > > > > > > > > - We need to document that if driver does not scan extended > > > > > > capbilities it will not find them. > > > > > > > > > > This is implicit since I remember we don't have such documentation for > > > > > pci capability, anything makes pcie special? > > > > > > > > yes - the fact that there are tons of existing drivers expecting > > > > everything in standard space. > > > > > > > > > > > > > > And existing drivers do not scan them. So what is safe > > > > > > to put there? vendor specific? extra access types? > > > > > > > > > > For PASID at least, since it's a PCI-E feature, vendor specific should > > > > > be fine. Not sure about legacy MMIO then. > > > > > > > > > > > Can we make scanning these mandatory in future drivers? future > > > > > > devices? > > > > > > I guess we can add a feature bit to flag that. > > > > > > > > > > For PASID, it doesn't need this, otherwise we may duplicate transport > > > > > specific features. > > > > > > > > i don't get it. what does PASID have to do with it? > > > > > > My proposal is to allow PASID capability to be placed on top. > > > > Assuming you mean a patch applied on top of this one. > > > > > So what > > > I meant is: > > > > > > if the driver needs to use PASID, it needs to scan extend capability > > > > > > So it is only used for future drivers. I think this applies to legacy > > > MMIO as well. > > > > sure > > > > > > A new feature will allow clean split at least: > > > > we make any new features and new devices that expect > > > > express capability depend on this new feature bit. > > > > > > > > > > Is accessing these possible from bios? > > > > > > > > > > Not at least for the two use cases now PASID or legacy MMIO. > > > > > > > > can't parse english here. what does this mean? > > > > > > I meant, it depends on the capability semantics. Both PASID and legacy > > > MMIO don't need to be accessed by BIOS. We can't change legacy BIOS to > > > use legacy MMIO bars. > > > > > > Thanks > > > > makes sense. > > > > > > now, imagine someone building a new device. if existing drivers are not > > a concern, it is possible to move capabilities all to extended space. is > > that possible while keeping the bios working? > > This is possible but I'm not sure it's worthwhile. What happens if the > device puts all capabilities in the extended space but the bios can't > scan there?
that's my question. can seabios access extended caps? > We can place them at both but it then doesn't address the > out of space issue. Things will be easier if we allow new > features/capabilities to be placed on the extended space. > > Thanks > > > > > > > > > > > > > > > > > > > > > > > So I like this one better as a basis - care reviewing it and adding > > > > > > stuff? > > > > > > > > > > There are very few differences and I will have a look. > > > > > > > > > > Thanks > > > > > > > > > > > > > > > > > -- > > > > > > MST > > > > > > > > > > > > --------------------------------------------------------------------- To unsubscribe, e-mail: virtio-dev-unsubscr...@lists.oasis-open.org For additional commands, e-mail: virtio-dev-h...@lists.oasis-open.org