Graphics workaround for AMD IOMMU systems
Joerg Roedel
joerg.roedel at amd.com
Mon Jun 15 03:08:25 PDT 2009
On Sat, Jun 13, 2009 at 04:01:30PM -0700, Chris Wright wrote:
> * Joerg Roedel (joro at 8bytes.org) wrote:
> > On Fri, Jun 12, 2009 at 12:28:02PM -0700, Chris Wright wrote:
> > > * Bhavna Sarathy (bnagendr at redhat.com) wrote:
> > > > +#define IS_GFX_DEVICE(pdev) ((pdev->class >> 16) == PCI_BASE_CLASS_DISPLAY)
> > >
> > > I think this is too permissive for upstream, and a blacklist would
> > > be better. So more like:
> >
> > Better would be if there were no workaround at all for this. Not for
> > VT-d and not for AMD IOMMU. But VT-d has it upstream and it doesn't look
> > like it will be removed anytime soon. This somehow forces such a nasty
> > workaround for AMD IOMMU in upstream code too :-(
>
> I agree, it's nasty, you don't have to take it ;-) I'm just looking for
> a way to limit the damage if you want to accept a work around.
Having no one at all is also no way to go in this situation :)
> > > static const struct pci_device_id pci_broken_gfx_ids[] = {
> > > /* Add your favorite busted card here */
> > > { } /* terminate list */
> > > };
> > >
> > > static inline bool is_broken_gfx_device(struct pci_device *pdev)
> > > {
> > > struct pci_device_id *broken = NULL
> > >
> > > broken = pci_id_match(pci_broken_gfx_ids, pdev);
> > > WARN(broken, "IOMMU: graphics device %s is broken with IOMMU, "
> > > "disabling IOMMU protection for this device\n",
> > > pci_name(pdev));
> > > return !!broken;
> > > }
> > >
> > > This should be sharable between VT-d and AMD IOMMU.
> >
> > I think its better to match against the driver name instead of device
> > ids because we only need this for crappy drivers.
>
> Ah, you mean for devices where there's a reasonably functional open
> source driver as well as a busted proprietary driver? Makes sense.
Yes, somehow this way. Current idea is to count the dma-mappings per
dma_ops domain to make sure there are no mappings pending when a broken
driver binds to the gfx device. Then we could check in the driver bind
path for the driver names on the blacklist and put the device into a
direct mapped domain if there are no mappings pending for the device.
Joerg
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