[PATCH 3.13 044/187] x86_64/entry/xen: Do not invoke espfix64 on Xen
ben at decadent.org.uk
Wed Sep 17 11:25:51 UTC 2014
On Mon, 2014-09-15 at 15:07 -0700, Kamal Mostafa wrote:
> 126.96.36.199 -stable review patch. If anyone has any objections, please let me know.
> From: Andy Lutomirski <luto at amacapital.net>
> commit 7209a75d2009dbf7745e2fd354abf25c3deb3ca3 upstream.
> This moves the espfix64 logic into native_iret. To make this work,
> it gets rid of the native patch for INTERRUPT_RETURN:
> INTERRUPT_RETURN on native kernels is now 'jmp native_iret'.
> This changes the 16-bit SS behavior on Xen from OOPSing to leaking
> some bits of the Xen hypervisor's RSP (I think).
> [ hpa: this is a nonzero cost on native, but probably not enough to
> measure. Xen needs to fix this in their own code, probably doing
> something equivalent to espfix64. ]
> Signed-off-by: Andy Lutomirski <luto at amacapital.net>
> Link: http://email@example.com
> Signed-off-by: H. Peter Anvin <hpa at linux.intel.com>
> Signed-off-by: Kamal Mostafa <kamal at canonical.com>
There's another fix related to espfix on Xen, commit 8762e5092828
("x86/espfix/xen: Fix allocation of pages for paravirt page tables").
But I'm not sure whether it's actually needed after this.
Beware of programmers who carry screwdrivers. - Leonard Brandwein
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