xen: use iret for return from 64b kernel to 32b usermode
authorJeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
Wed, 25 Nov 2009 21:15:38 +0000 (13:15 -0800)
committerJeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
Thu, 3 Dec 2009 19:14:54 +0000 (11:14 -0800)
commit6aaf5d633bb6cead81b396d861d7bae4b9a0ba7e
tree3bd503d3e7b9aa84c1ab618c53c1b1eadad87c83
parent922cc38ab71d1360978e65207e4a4f4988987127
xen: use iret for return from 64b kernel to 32b usermode

If Xen wants to return to a 32b usermode with sysret it must use the
right form.  When using VCGF_in_syscall to trigger this, it looks at
the code segment and does a 32b sysret if it is FLAT_USER_CS32.
However, this is different from __USER32_CS, so it fails to return
properly if we use the normal Linux segment.

So avoid the whole mess by dropping VCGF_in_syscall and simply use
plain iret to return to usermode.

Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
Acked-by: Jan Beulich <jbeulich@novell.com>
Cc: Stable Kernel <stable@kernel.org>
arch/x86/xen/xen-asm_64.S