On Mon, 20 Jun 2016 16:23:07 -0600
Eric Blake <ebl...@redhat.com> wrote:
> 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/
>
Thanks, updated:
diff --git a/hw/vfio/pci.c b/hw/vfio/pci.c
index 36d5e00..2418b93 100644
--- a/hw/vfio/pci.c
+++ b/hw/vfio/pci.c
@@ -1796,7 +1796,7 @@ static int vfio_add_ext_cap(VFIOPCIDevice *vdev)
* 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
+ * part for identifying absence of capabilities in a root complex register
* block. If the ID still exists after adding capabilities, switch back to
* zero. We'll mark this entire first dword as emulated for this purpose.
*/
