iommu/amd: Apply workaround for ATS write permission check

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commit 358875fd52 upstream.

The AMD Family 15h Models 30h-3Fh (Kaveri) BIOS and Kernel Developer's
Guide omitted part of the BIOS IOMMU L2 register setup specification.
Without this setup the IOMMU L2 does not fully respect write permissions
when handling an ATS translation request.

The IOMMU L2 will set PTE dirty bit when handling an ATS translation with
write permission request, even when PTE RW bit is clear. This may occur by
direct translation (which would cause a PPR) or by prefetch request from
the ATC.

This is observed in practice when the IOMMU L2 modifies a PTE which maps a
pagecache page. The ext4 filesystem driver BUGs when asked to writeback
these (non-modified) pages.

Enable ATS write permission check in the Kaveri IOMMU L2 if BIOS has not.

Signed-off-by: Jay Cornwall <jay@jcornwall.me>
Signed-off-by: Joerg Roedel <jroedel@suse.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

...

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Jay Cornwall 2016-02-10 15:48:01 -06:00 • committed by Greg Kroah-Hartman

parent d1c623c9c2

commit ad0f9dade9

1 changed files with 29 additions and 0 deletions

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drivers/iommu/amd_iommu_init.c

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