[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: [Xen-devel] [PATCH] amd iommu: re-enable iommu msi if dom0 disabled it



On 06/08/2012 04:08 PM, Jan Beulich wrote:
On 08.06.12 at 15:41, Wei Wang<wei.wang2@xxxxxxx>  wrote:
On 06/08/2012 03:31 PM, Andrew Cooper wrote:
On 08/06/12 14:28, Wei Wang wrote:
I found that recent dom0 (e.g 3.4 pv_ops) disables iommu msi capability
for some reasons and iommu cannot generate any interrupts in this case.
Attached patch re-enables it in device assignment.

Under which circumstances should dom0 able to play with the IOMMUs ?
Surely the fact that dom0 can play with the IOMMUs is a bug in itself.

It looks like some generic msi/pci codes disable it, not the Linux iommu
driver itself, which is only loaded on bare metal. AMD IOMMU expose
interrupt capability as a normal msi block. So the general pci/msi layer
of dom0 might touch it...

In that case it wouldn't be on pv-ops alone (which your patch
says).

Yes, probably upstream Linux also has this issue. I will check that. But I did not see this issue on 3.2 pv_ops & 2.6 pv_ops.

Also, your patch using IOMMU_CONTROL_ENABLED instead of
PCI_MSI_FLAGS_ENABLE is quite misleading (as it hides the fact
the what you play with is not IOMMU-specific).

Thanks, I will use PCI_MSI_FLAGS_ENABLE in next post.

Wei

Jan





_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxx
http://lists.xen.org/xen-devel


 


Rackspace

Lists.xenproject.org is hosted with RackSpace, monitoring our
servers 24x7x365 and backed by RackSpace's Fanatical Support®.