Messages in this thread | | | Date | Tue, 29 Oct 2013 15:59:53 +0000 | From | Gordan Bobic <> | Subject | Re: [Xen-devel] [v1 1/2] xen/p2m: Create identity mappings for PFNs beyound E820 and PCI BARs |
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On Tue, 29 Oct 2013 11:11:29 -0400, Konrad Rzeszutek Wilk <konrad.wilk@oracle.com> wrote: > On Tue, Oct 29, 2013 at 02:55:13PM +0000, Jan Beulich wrote: >> >>> On 29.10.13 at 15:45, Konrad Rzeszutek Wilk >> <konrad.wilk@oracle.com> wrote: >> > On Tue, Oct 29, 2013 at 08:23:30AM +0000, Jan Beulich wrote: >> >> >>> On 28.10.13 at 17:58, Konrad Rzeszutek Wilk >> <konrad.wilk@oracle.com> wrote: >> >> > On Fri, Oct 25, 2013 at 04:08:19PM -0600, Bjorn Helgaas wrote: >> >> >> If you can look at PCI host bridge apertures instead of BARs, >> that >> >> >> would solve both problems. Reassigning those apertures is >> >> >> theoretically possible but is not even a gleam in our eyes >> yet. >> >> > >> >> > <nods> I think I have to have both (BARs and host bridge >> apertures) as when >> >> > we do PCI passthrough to a guest - we might do it without a >> bridge. >> >> >> >> Why? Aren't the host bridge ranges necessarily a superset of the >> >> individual devices' BARs? >> > >> > Yes. But when you pass in a PCI device to a PV guest you don't >> pass in the >> > bridge. Just the PCI device itself. >> >> Right you are. Which means that basing the whole logic on the >> PCI device BARs is likely wrong anyway, not just because it >> doesn't account for other MMIO ranges. > > Right, but that is OK. When you pass in a PCI device to a PV guest > you > only care about that specific device driver being able to access its > BARs.
Maybe I'm reading this wrong, but my understanding is that you cannot pass PCI bridges to domU anyway (in HVM - I tried). Is that not the case? I'm particularly interested in this for two reasons:
1) Some GPUs (Nvidia?) use bus resets to reset the GPU
2) Multi-GPU cards (e.g. GTX690/Grid K2) come with a PCIe bridge of their own. I am successfully passing a modified GTX680 (as either a Grid K2 or Quadro K5000) to a domU, but have completely failed to get a modified GTX690 (Grid K2, exact same GPU as the GTX680) to work with passthru. The only theory I have is that the extra PCIe bridge is the problem (possibly a compound problem that only manigests when there is a PLX (as per GTX690) PCIe bridge behind a NF200 PCIe bridge, behind an Intel PCIe bridge.
Gordan
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