On 23/09/15 16:34, Jan Beulich wrote:
Us extending the GDT limit past the Xen descriptors so far meant that
guests (including user mode programs) accessing any descriptor table
slot above the original OS'es limit but below the first Xen descriptor
caused a #PF, converted to a #GP in our #PF handler. Which is quite
different from the native behavior, where some of such accesses (LAR
and LSL) don't fault. Mimic that behavior by mapping a blank page into
unused slots.
While not strictly required, treat the LDT the same for consistency.
Reported-by: Andrew Cooper <andrew.coop...@citrix.com>
Signed-off-by: Jan Beulich <jbeul...@suse.com>
Oh - thanks for doing this. (Luckily, I hadn't yet had enough time to
look into it.)
Reviewed-by: Andrew Cooper <andrew.coop...@citrix.com>
---
Not sure about 4.6 here: Beyond Andrew noticing I don't think anyone
ran into this issue in a real world environment, and hence it doesn't
seem to be too critical to get this fixed.
This bug causes unexpected #GP faults being handed to PV guests which
would not occur on native, when using the `lsl` and `lsr` instructions.
I expect it is the rarity of those instructions which is why this has
gone unnoticed for so long.
It probably should be backported.
~Andrew
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