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Re: [Xen-devel] [PATCH] x86/efi: Reserve EFI properties table

Hi Andrew,

On 08/05/17 17:29, Andrew Cooper wrote:
On 08/05/17 17:17, Ross Lagerwall wrote:
Some EFI firmware implementations may place the EFI properties table in
RAM marked as BootServicesData, which Xen does not consider as reserved.
When dom0 tries to access the EFI properties table (which Linux >= 4.4
does), it crashes with a page fault.

The pagefault is just a side effect of Linux blindly assuming that the
ioremap() request succeeded.

From Xen's point of view, Dom0 tries to map a page which doesn't belong
to dom_xen, resulting a permission failure.

  Fix this by unconditionally
marking the EFI properties table as reserved in the E820, much like is
done with the dmi regions.

Signed-off-by: Ross Lagerwall <ross.lagerwall@xxxxxxxxxx>

Reviewed-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>

This is probably also 4.9 material.

It looks like Jan had some comments on this patch. I haven't seen any reply from Ross, I will wait before looking from a release perspective.


Julien Grall

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