This is an archived copy of the Xen.org mailing list, which we have preserved to ensure that existing links to archives are not broken. The live archive, which contains the latest emails, can be found at http://lists.xen.org/
Home Products Support Community News


Re: [Xen-devel] Re: IOMMU faults

At 14:32 +0100 on 24 Jun (1308925934), Tim Deegan wrote:
> At 11:28 +0100 on 16 Jun (1308223697), Jean Guyader wrote:
> > > Of course, even with this patch, my original question still stands:
> > > should Xen do something more assertive in the IOMMU fault handler?
> > 
> > What we really want to achive here is to stop DMA on this device.
> > One way of doing it is to perform a proper PCI reset (FLR, secondary
> > bus reset, ...) when that happens.
> I think that's more or less a consensus then, that we should try to
> stop the device from the IOMMU fault handler.
> Looking at your patch in a bit more detail, I see two things that worry
> me.  The first is that the new pci_reset_device() function does nothing
> at all if the device isn't one of the particular graphics cards it know
> about!
> The second is this comment: 
> > +    /* Leave CMD MEMORY set otherwise the platform can crashe during FLR */
> > +    pci_conf_write16(bus, d, f, PCI_COMMAND, 2);
> which implies that my current approach of just disabling the card might
> have pretty bad conequences.  Can you expand on that?  Would it be
> better just to mask out PCI_COMMAND_MASTER?  And if I do that do I need
> to try and issue a reset as well (i.e. are there cards that are known to
> ignore this bit?)



Tim Deegan <Tim.Deegan@xxxxxxxxxx>
Principal Software Engineer, Xen Platform Team
Citrix Systems UK Ltd.  (Company #02937203, SL9 0BG)

Xen-devel mailing list