On 06/20/2016 04:04 PM, Alex Williamson wrote: > The kernel currently exposes the SR-IOV capability as read-only > through vfio-pci. This is sufficient to protect the host kernel, but > has the potential to confuse guests without further virtualization. > In particular, OVMF tries to size the VF BARs and comes up with absurd > results, ending with an assert. There's not much point in adding > virtualization to a read-only capability, so we simply hide it for > now. If the kernel ever enables SR-IOV virtualization, we should > easily be able to test it through VF BAR sizing or explicit flags. > > Testing whether we should parse extended capabilities is also pulled > into the function to keep these assumptions in one place. > > Signed-off-by: Alex Williamson <alex.william...@redhat.com> > ---
> + * Extended capabilities are chained with each pointing to the next, so > we > + * can drop anything other than the head of the chain simply by modifying > + * the previous next pointer. For the head of the chain, we can modify > the > + * capability ID to something that cannot match a valid capability. ID > + * 0 is reserved for this since absence of capabilities is indicated by > + * 0 for the ID, version, AND next pointer. However, > pcie_add_capability() > + * uses ID 0 as reserved for list management and will incorrectly match > and > + * assert if we attempt to pre-load the head of the chain with with this > + * ID. Use ID 0xFFFF temporarily since it is also seems to be reserved > in > + * part for identifying abscense of capabilities in a root complex > register s/abscense/absence/ -- Eric Blake eblake redhat com +1-919-301-3266 Libvirt virtualization library http://libvirt.org
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