Commit:     8b15114434998a78aa50f8559d69c7a400cff267
Parent:     9226d125d94c7e4964dd41cc5e9ca2ff84091d01
Author:     Zachary Amsden <[EMAIL PROTECTED]>
AuthorDate: Tue Feb 13 13:26:21 2007 +0100
Committer:  Andi Kleen <[EMAIL PROTECTED]>
CommitDate: Tue Feb 13 13:26:21 2007 +0100

    [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 <[EMAIL PROTECTED]>
    Signed-off-by: Andi Kleen <[EMAIL PROTECTED]>
    Cc: Andi Kleen <[EMAIL PROTECTED]>
    Cc: Jeremy Fitzhardinge <[EMAIL PROTECTED]>
    Cc: Rusty Russell <[EMAIL PROTECTED]>
    Cc: Chris Wright <[EMAIL PROTECTED]>
    Signed-off-by: Andrew Morton <[EMAIL PROTECTED]>
 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 cfae587..05be774 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)
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