Re: [dm-devel] AMD-Vi IO_PAGE_FAULTs and ata3.00: failed command: READ FPDMA QUEUED errors since Linux 4.0

[Joerg Roedel <joro@8bytes.org>]

On Tue, Sep 29, 2015 at 11:58:10AM -0400, Mikulas Patocka wrote:
> On Tue, 29 Sep 2015, Joerg Roedel wrote:
> There was a patch (34b48db66e08ca1c1bc07cf305d672ac940268dc) that 
> increased default block request size. That patch triggers AMD-Vi page 
> faults. The bug may be in ATA driver, in ATA controller on in AMD-Vi 
> driver or hardware. I didn't see anything in that thread that proves that 
> the bug in not in AMD-Vi IOMMU.
> 
> The bug probably existed even before kernel 3.19, but it was masked by the 
> fact that I/O request size was artifically capped. Bisecting probably 
> won't find it, as it may have existed since ever.

Okay, I see. But as long as the request-size is not bigger than 128MB
(the biggest chunk the AMD IOMMU driver can map at once), I don't see
how the IOMMU driver could be at fault.

Which ATA driver is in use when this happens and are there instructions
on how to reproduce the issue?

Alternativly someone who can reproduce it should trace the calls to
__map_single and __unmap_single in the AMD IOMMU driver to find out
whether the addresses which the faults happen on are really mapped, or
at least requested from the AMD IOMMU driver.



	Joerg