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 <[email protected]> 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 <[email protected]> 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 <[email protected]> > > > > Signed-off-by: Parav Pandit <[email protected]> > > > > > > Can you explain the differences compared to what I've used to propose? > > > > > > https://www.mail-archive.com/[email protected]/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? 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? > > > > 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: [email protected] For additional commands, e-mail: [email protected]
