Re: [Xen-devel] Failure to get memory for GATT table, again

[Jacob Gorm Hansen <jacobg@xxxxxxx>]

Ian Pratt wrote:
> > Just to recap, this seems like a bug in Xen or Xenlinux. 
> > MMUEXT_SET_FOREIGNDOM seems to expect the granted pages to be 
> > owned by 
> > the grantee already, instead of the granter. I've disabled 
> > the check in 
> > Xen, and fglrx now proceeds to take down the machine when I start X. 
> > Perhaps it would be better to spend the time on the open drivers at 
> > http://r300.sourceforge.net/ , or wait for ATI to discover Xen.
>
> It sounds rather more like an agp driver that's taking liberties to me.
> The fact that disabling the check takes the machine down seems to
> suggest its there for a purpose :-)
Could you explain what MMUEXT_SET_FOREIGNDOM is supposed to do, and in
particular who should own the pages before and after the call? Still,
this check fail _before_ fglrx is loaded. Right now intel-agp refuses to
load on my machine with an ATI card inside, and all the software on the
machine at that point comes from the xen-tree.

What happens is:

1) the xen_contig_mem function frees some mem.
2) the xen_contig_mem function allocs some other mem instead. dom0 now 
owns that mem.
3) dom0 tries to give that mem away to some mysterious other domain
using MMU_SET_FOREIGNDOM (if I understand the purpose of that call
correctly).
4) Xen complains because the to-be-given-away mem is owned by dom0
rather than the mysterious foreign domain.

I agree that fglrx is also buggy, but the failing ownership check has
nothing to do with that.

Thanks,

Jacob




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