Re: [PATCH 00/19] Fix Intel IOMMU breakage in kdump kernel

[David Woodhouse]

On Sat, 2015-06-13 at 08:47 +0200, Joerg Roedel wrote:
> Hi,
> 
> as David Woodhouse pointed out, my fixes and cleanups for
> the original patch-set turned out to be a complete rewrite.
> So to have a cleaner history of the feature and to make
> backporting easier, here is a rewrite of my changes based on
> v4.1-rc7.
> 
> Some additional issues have been fixed by this rewrite, like
> a kdump-kernel boot panic with 'iommu=pt' and support for
> copying the extended root-entry and context table formats
> has been added.

This looks much better than before; thanks.

However, it's still fairly gratuitous for all non-broken hardware, and
will tend to hide hardware and driver bugs during testing of new
hardware.

I'd much rather see this limited to a blacklist of known-broken
devices, an accompanied by a kernel message along the lines of

 'Preserving VT-d page tables for broken HP device xxxx:xxxx'

For *any* device which isn't so broken that it craps itself on taking a
DMA fault and cannot be reset, this page table copy shouldn't be
needed, right?


-- 
David Woodhouse                            Open Source Technology Centre
David.Woodhouse@xxxxxxxxx                              Intel Corporation

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