[Xen-devel] [PATCH v4 07/10] x86: process: Introduce helper to switch iopl mask

[Josh Triplett <josh@xxxxxxxxxxxxxxxx>]

This simplifies __switch_to a bit, and will make it easier to make iopl
optional later.

Signed-off-by: Josh Triplett <josh@xxxxxxxxxxxxxxxx>
---
 arch/x86/kernel/process-io.h | 13 +++++++++++++
 arch/x86/kernel/process_32.c |  9 +--------
 2 files changed, 14 insertions(+), 8 deletions(-)

diff --git a/arch/x86/kernel/process-io.h b/arch/x86/kernel/process-io.h
index ffa65e8..6d4f147 100644
--- a/arch/x86/kernel/process-io.h
+++ b/arch/x86/kernel/process-io.h
@@ -24,4 +24,17 @@ static inline int copy_io_bitmap(struct task_struct *me,
        return 0;
 }
 
+static inline void switch_iopl_mask(struct thread_struct *prev,
+                                   struct thread_struct *next)
+{
+        /*
+         * 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);
+}
+
 #endif /* _X86_KERNEL_PROCESS_IO_H */
diff --git a/arch/x86/kernel/process_32.c b/arch/x86/kernel/process_32.c
index b55f78e..3b82293 100644
--- a/arch/x86/kernel/process_32.c
+++ b/arch/x86/kernel/process_32.c
@@ -265,14 +265,7 @@ __switch_to(struct task_struct *prev_p, struct task_struct 
*next_p)
         */
        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);
+       switch_iopl_mask(prev, next);
 
        /*
         * If it were not for PREEMPT_ACTIVE we could guarantee that the
-- 
2.1.1


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