Re: [PATCH 0/2] iommu: Fix regression in IOMMU grouping

From: Joerg Roedel
Date: Thu Sep 25 2014 - 10:40:43 EST

On Fri, Sep 19, 2014 at 10:03:00AM -0600, Alex Williamson wrote:
> We've had surprisingly little fallout from the DMA alias changes, but
> unfortunately one regression has popped up. We have an AMD system
> that seems to use the SATA controller to master transactions for the
> legacy IDE controller and they are different slots on the root complex.
> The IVRS reports 00:11.0 (SATA) as an alias from 00:14.1 (IDE), which
> doesn't work with the new, converged PCI IOMMU grouping code, where
> we've made a simplifying assumption that aliases will be to the same
> slot.
> To fix this, we need to rip out that assumption and write the alias
> search code that I was unable to come up with previously. I think
> this can now do the chaining of aliases, which I referenced in the
> removed comments. Any sort of multi-level aliases are exceptionally
> unlikely, but I think this code can now handle whatever firmware and
> alias quirks can throw at it.

Applied to core, thanks Alex.

> I know this is late for 3.17, but this is a regression from the prior
> code. If reviews and testing can give us the confidence to put it in
> for 3.17, that would be my preference. I've also marked it for stable
> in case we want to loop back through that way. Thanks,

The change is too big to make it into v3.17 at this point of the
development cycle, so I queued it up for the upcoming merge window.


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