linux-kernel - [PATCH v4 09/10] x86: process: Introduce helper to switch IO bitmap

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Date:	Sun, 2 Nov 2014 09:32:55 -0800
From:	Josh Triplett <josh@...htriplett.org>
To:	"H. Peter Anvin" <hpa@...or.com>, Ingo Molnar <mingo@...hat.com>,
	Kees Cook <keescook@...omium.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	linux-kernel@...r.kernel.org,
	virtualization@...ts.linux-foundation.org, x86@...nel.org,
	xen-devel@...ts.xenproject.org
Subject: [PATCH v4 09/10] x86: process: Introduce helper to switch IO bitmap

This simplifies __switch_to_xtra, and will make it easier to make IO
optional later.

Signed-off-by: Josh Triplett <josh@...htriplett.org>
---
 arch/x86/kernel/process-io.h | 23 +++++++++++++++++++++++
 arch/x86/kernel/process.c    | 14 +-------------
 2 files changed, 24 insertions(+), 13 deletions(-)

diff --git a/arch/x86/kernel/process-io.h b/arch/x86/kernel/process-io.h
index 012c1d5..e48d5c9 100644
--- a/arch/x86/kernel/process-io.h
+++ b/arch/x86/kernel/process-io.h
@@ -57,4 +57,27 @@ static inline void switch_iopl_mask(struct thread_struct *prev,
                 set_iopl_mask(next->iopl);
 }
 
+static inline void switch_io_bitmap(struct tss_struct *tss,
+				    struct task_struct *prev_p,
+				    struct task_struct *next_p)
+{
+        struct thread_struct *prev, *next;
+        prev = &prev_p->thread;
+        next = &next_p->thread;
+
+        if (test_tsk_thread_flag(next_p, TIF_IO_BITMAP)) {
+                /*
+                 * Copy the relevant range of the IO bitmap.
+                 * Normally this is 128 bytes or less:
+                 */
+                memcpy(tss->io_bitmap, next->io_bitmap_ptr,
+                       max(prev->io_bitmap_max, next->io_bitmap_max));
+        } else if (test_tsk_thread_flag(prev_p, TIF_IO_BITMAP)) {
+                /*
+                 * Clear any possible leftover bits:
+                 */
+                memset(tss->io_bitmap, 0xff, prev->io_bitmap_max);
+        }
+}
+
 #endif /* _X86_KERNEL_PROCESS_IO_H */
diff --git a/arch/x86/kernel/process.c b/arch/x86/kernel/process.c
index 37b45ca..7ac01bf 100644
--- a/arch/x86/kernel/process.c
+++ b/arch/x86/kernel/process.c
@@ -211,19 +211,7 @@ void __switch_to_xtra(struct task_struct *prev_p, struct task_struct *next_p,
 			hard_enable_TSC();
 	}
 
-	if (test_tsk_thread_flag(next_p, TIF_IO_BITMAP)) {
-		/*
-		 * Copy the relevant range of the IO bitmap.
-		 * Normally this is 128 bytes or less:
-		 */
-		memcpy(tss->io_bitmap, next->io_bitmap_ptr,
-		       max(prev->io_bitmap_max, next->io_bitmap_max));
-	} else if (test_tsk_thread_flag(prev_p, TIF_IO_BITMAP)) {
-		/*
-		 * Clear any possible leftover bits:
-		 */
-		memset(tss->io_bitmap, 0xff, prev->io_bitmap_max);
-	}
+	switch_io_bitmap(tss, prev_p, next_p);
 	propagate_user_return_notify(prev_p, next_p);
 }
 
-- 
2.1.1

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