diff options
| author | Zachary Amsden <zach@vmware.com> | 2007-02-13 13:26:21 +0100 |
|---|---|---|
| committer | Andi Kleen <andi@basil.nowhere.org> | 2007-02-13 13:26:21 +0100 |
| commit | 8b15114434998a78aa50f8559d69c7a400cff267 (patch) | |
| tree | 2385fd562d0f625baaf32e75dd7dbedc966e9635 /arch/i386/kernel/process.c | |
| parent | 9226d125d94c7e4964dd41cc5e9ca2ff84091d01 (diff) | |
[PATCH] i386: iOPL handling for paravirt guests
I found a clever way to make the extra IOPL switching invisible to
non-paravirt compiles - since kernel_rpl is statically defined to be zero
there, and only non-zero rpl kernel have a problem restoring IOPL, as popf
does not restore IOPL flags unless run at CPL-0.
Signed-off-by: Zachary Amsden <zach@vmware.com>
Signed-off-by: Andi Kleen <ak@suse.de>
Cc: Andi Kleen <ak@suse.de>
Cc: Jeremy Fitzhardinge <jeremy@xensource.com>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Cc: Chris Wright <chrisw@sous-sol.org>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Diffstat (limited to 'arch/i386/kernel/process.c')
| -rw-r--r-- | arch/i386/kernel/process.c | 9 |
1 files changed, 9 insertions, 0 deletions
diff --git a/arch/i386/kernel/process.c b/arch/i386/kernel/process.c index cfae587bf7d..05be7741335 100644 --- a/arch/i386/kernel/process.c +++ b/arch/i386/kernel/process.c @@ -670,6 +670,15 @@ struct task_struct fastcall * __switch_to(struct task_struct *prev_p, struct tas load_TLS(next, cpu); /* + * Restore IOPL if needed. In normal use, the flags restore + * in the switch assembly will handle this. But if the kernel + * is running virtualized at a non-zero CPL, the popf will + * not restore flags, so it must be done in a separate step. + */ + if (get_kernel_rpl() && unlikely(prev->iopl != next->iopl)) + set_iopl_mask(next->iopl); + + /* * Now maybe handle debug registers and/or IO bitmaps */ if (unlikely((task_thread_info(next_p)->flags & _TIF_WORK_CTXSW) |