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From: "tip-bot2 for Thomas Gleixner" <tip-bot2@linutronix.de>
To: linux-tip-commits@vger.kernel.org
Cc: Linus Torvalds <torvalds@linux-foundation.org>,
	Thomas Gleixner <tglx@linutronix.de>,
	"Peter Zijlstra (Intel)" <peterz@infradead.org>,
	Ingo Molnar <mingo@kernel.org>, Borislav Petkov <bp@alien8.de>,
	linux-kernel@vger.kernel.org
Subject: [tip: x86/iopl] x86/ioperm: Add bitmap sequence number
Date: Fri, 15 Nov 2019 21:12:29 -0000
Message-ID: <157385234967.12247.10518024307495865043.tip-bot2@tip-bot2> (raw)
In-Reply-To: <20191113210104.790774205@linutronix.de>

The following commit has been merged into the x86/iopl branch of tip:

Commit-ID:     209c34d3c2de01a5dfe428b8b79fdb913dd76334
Gitweb:        https://git.kernel.org/tip/209c34d3c2de01a5dfe428b8b79fdb913dd76334
Author:        Thomas Gleixner <tglx@linutronix.de>
AuthorDate:    Wed, 13 Nov 2019 21:42:51 +01:00
Committer:     Thomas Gleixner <tglx@linutronix.de>
CommitterDate: Thu, 14 Nov 2019 20:15:04 +01:00

x86/ioperm: Add bitmap sequence number

Add a globally unique sequence number which is incremented when ioperm() is
changing the I/O bitmap of a task. Store the new sequence number in the
io_bitmap structure and compare it with the sequence number of the I/O
bitmap which was last loaded on a CPU. Only update the bitmap if the
sequence is different.

That should further reduce the overhead of I/O bitmap scheduling when there
are only a few I/O bitmap users on the system.

The 64bit sequence counter is sufficient. A wraparound of the sequence
counter assuming an ioperm() call every nanosecond would require about 584
years of uptime.

Suggested-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20191113210104.790774205@linutronix.de


---
 arch/x86/include/asm/io_bitmap.h |  1 +-
 arch/x86/include/asm/processor.h |  3 ++-
 arch/x86/kernel/cpu/common.c     |  1 +-
 arch/x86/kernel/ioport.c         |  5 ++++-
 arch/x86/kernel/process.c        | 38 ++++++++++++++++++++++---------
 5 files changed, 38 insertions(+), 10 deletions(-)

diff --git a/arch/x86/include/asm/io_bitmap.h b/arch/x86/include/asm/io_bitmap.h
index 1a12b9f..d63bd5a 100644
--- a/arch/x86/include/asm/io_bitmap.h
+++ b/arch/x86/include/asm/io_bitmap.h
@@ -5,6 +5,7 @@
 #include <asm/processor.h>
 
 struct io_bitmap {
+	u64		sequence;
 	/* The maximum number of bytes to copy so all zero bits are covered */
 	unsigned int	max;
 	unsigned long	bitmap[IO_BITMAP_LONGS];
diff --git a/arch/x86/include/asm/processor.h b/arch/x86/include/asm/processor.h
index c949e0e..40bb0f7 100644
--- a/arch/x86/include/asm/processor.h
+++ b/arch/x86/include/asm/processor.h
@@ -361,6 +361,9 @@ struct entry_stack_page {
  * All IO bitmap related data stored in the TSS:
  */
 struct x86_io_bitmap {
+	/* The sequence number of the last active bitmap. */
+	u64			prev_sequence;
+
 	/*
 	 * Store the dirty size of the last io bitmap offender. The next
 	 * one will have to do the cleanup as the switch out to a non io
diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c
index 3aee167..79dd544 100644
--- a/arch/x86/kernel/cpu/common.c
+++ b/arch/x86/kernel/cpu/common.c
@@ -1862,6 +1862,7 @@ void cpu_init(void)
 	tss_setup_ist(tss);
 	tss->x86_tss.io_bitmap_base = IO_BITMAP_OFFSET_INVALID;
 	tss->io_bitmap.prev_max = 0;
+	tss->io_bitmap.prev_sequence = 0;
 	memset(tss->io_bitmap.bitmap, 0xff, sizeof(tss->io_bitmap.bitmap));
 	set_tss_desc(cpu, &get_cpu_entry_area(cpu)->tss.x86_tss);
 
diff --git a/arch/x86/kernel/ioport.c b/arch/x86/kernel/ioport.c
index 05f77f3..7c1ab5c 100644
--- a/arch/x86/kernel/ioport.c
+++ b/arch/x86/kernel/ioport.c
@@ -14,6 +14,8 @@
 #include <asm/io_bitmap.h>
 #include <asm/desc.h>
 
+static atomic64_t io_bitmap_sequence;
+
 /*
  * this changes the io permissions bitmap in the current task.
  */
@@ -72,6 +74,9 @@ long ksys_ioperm(unsigned long from, unsigned long num, int turn_on)
 
 	/* Update the thread data */
 	iobm->max = bytes;
+	/* Update the sequence number to force an update in switch_to() */
+	iobm->sequence = atomic64_add_return(1, &io_bitmap_sequence);
+
 	/*
 	 * Store the bitmap pointer (might be the same if the task already
 	 * head one). Set the TIF flag, just in case this is the first
diff --git a/arch/x86/kernel/process.c b/arch/x86/kernel/process.c
index 39c495d..eec7987 100644
--- a/arch/x86/kernel/process.c
+++ b/arch/x86/kernel/process.c
@@ -354,6 +354,28 @@ void arch_setup_new_exec(void)
 	}
 }
 
+static void switch_to_update_io_bitmap(struct tss_struct *tss,
+				       struct io_bitmap *iobm)
+{
+	/*
+	 * Copy at least the byte range of the incoming tasks bitmap which
+	 * covers the permitted I/O ports.
+	 *
+	 * If the previous task which used an I/O bitmap had more bits
+	 * permitted, then the copy needs to cover those as well so they
+	 * get turned off.
+	 */
+	memcpy(tss->io_bitmap.bitmap, iobm->bitmap,
+	       max(tss->io_bitmap.prev_max, iobm->max));
+
+	/*
+	 * Store the new max and the sequence number of this bitmap
+	 * and a pointer to the bitmap itself.
+	 */
+	tss->io_bitmap.prev_max = iobm->max;
+	tss->io_bitmap.prev_sequence = iobm->sequence;
+}
+
 static inline void switch_to_bitmap(struct thread_struct *next,
 				    unsigned long tifp, unsigned long tifn)
 {
@@ -363,18 +385,14 @@ static inline void switch_to_bitmap(struct thread_struct *next,
 		struct io_bitmap *iobm = next->io_bitmap;
 
 		/*
-		 * Copy at least the size of the incoming tasks bitmap
-		 * which covers the last permitted I/O port.
-		 *
-		 * If the previous task which used an io bitmap had more
-		 * bits permitted, then the copy needs to cover those as
-		 * well so they get turned off.
+		 * Only copy bitmap data when the sequence number
+		 * differs. The update time is accounted to the incoming
+		 * task.
 		 */
-		memcpy(tss->io_bitmap.bitmap, next->io_bitmap->bitmap,
-		       max(tss->io_bitmap.prev_max, next->io_bitmap->max));
+		if (tss->io_bitmap.prev_sequence != iobm->sequence)
+			switch_to_update_io_bitmap(tss, iobm);
 
-		/* Store the new max and set io_bitmap_base valid */
-		tss->io_bitmap.prev_max = next->io_bitmap->max;
+		/* Enable the bitmap */
 		tss->x86_tss.io_bitmap_base = IO_BITMAP_OFFSET_VALID;
 
 		/*

  reply index

Thread overview: 53+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-11-13 20:42 [patch V3 00/20] x86/iopl: Prevent user space from using CLI/STI with iopl(3) Thomas Gleixner
2019-11-13 20:42 ` [patch V3 01/20] x86/ptrace: Prevent truncation of bitmap size Thomas Gleixner
2019-11-15 21:12   ` [tip: x86/iopl] " tip-bot2 for Thomas Gleixner
2019-11-13 20:42 ` [patch V3 02/20] x86/process: Unify copy_thread_tls() Thomas Gleixner
2019-11-13 21:10   ` Linus Torvalds
2019-11-13 21:41     ` Thomas Gleixner
2019-11-13 22:10       ` Linus Torvalds
2019-11-13 22:33         ` Thomas Gleixner
2019-11-13 21:44     ` Brian Gerst
2019-11-15 21:12   ` [tip: x86/iopl] " tip-bot2 for Thomas Gleixner
2019-11-13 20:42 ` [patch V3 03/20] x86/cpu: Unify cpu_init() Thomas Gleixner
2019-11-15 21:12   ` [tip: x86/iopl] " tip-bot2 for Thomas Gleixner
2019-11-13 20:42 ` [patch V3 04/20] x86/tss: Fix and move VMX BUILD_BUG_ON() Thomas Gleixner
2019-11-15 21:12   ` [tip: x86/iopl] " tip-bot2 for Thomas Gleixner
2019-11-13 20:42 ` [patch V3 05/20] x86/iopl: Cleanup include maze Thomas Gleixner
2019-11-15 21:12   ` [tip: x86/iopl] " tip-bot2 for Thomas Gleixner
2019-11-13 20:42 ` [patch V3 06/20] x86/ioperm: Simplify first ioperm() invocation logic Thomas Gleixner
2019-11-15 21:12   ` [tip: x86/iopl] " tip-bot2 for Thomas Gleixner
2019-11-13 20:42 ` [patch V3 07/20] x86/ioperm: Avoid bitmap allocation if no permissions are set Thomas Gleixner
2019-11-15 21:12   ` [tip: x86/iopl] " tip-bot2 for Thomas Gleixner
2019-11-13 20:42 ` [patch V3 08/20] x86/io: Speedup schedule out of I/O bitmap user Thomas Gleixner
2019-11-15 21:12   ` [tip: x86/iopl] " tip-bot2 for Thomas Gleixner
2019-11-13 20:42 ` [patch V3 09/20] x86/tss: Move I/O bitmap data into a seperate struct Thomas Gleixner
2019-11-15 21:12   ` [tip: x86/iopl] " tip-bot2 for Thomas Gleixner
2019-11-13 20:42 ` [patch V3 10/20] x86/ioperm: Move iobitmap data into a struct Thomas Gleixner
2019-11-15 21:12   ` [tip: x86/iopl] " tip-bot2 for Thomas Gleixner
2019-11-13 20:42 ` [patch V3 11/20] x86/ioperm: Add bitmap sequence number Thomas Gleixner
2019-11-15 21:12   ` tip-bot2 for Thomas Gleixner [this message]
2019-11-13 20:42 ` [patch V3 12/20] x86/ioperm: Move TSS bitmap update to exit to user work Thomas Gleixner
2019-11-13 21:19   ` Linus Torvalds
2019-11-13 21:21     ` Linus Torvalds
2019-11-13 21:44       ` Thomas Gleixner
2019-11-15 21:12   ` [tip: x86/iopl] " tip-bot2 for Thomas Gleixner
2019-11-13 20:42 ` [patch V3 13/20] x86/ioperm: Remove bitmap if all permissions dropped Thomas Gleixner
2019-11-15 21:12   ` [tip: x86/iopl] " tip-bot2 for Thomas Gleixner
2019-11-13 20:42 ` [patch V3 14/20] x86/ioperm: Share I/O bitmap if identical Thomas Gleixner
2019-11-15 21:12   ` [tip: x86/iopl] " tip-bot2 for Thomas Gleixner
2019-11-13 20:42 ` [patch V3 15/20] selftests/x86/ioperm: Extend testing so the shared bitmap is exercised Thomas Gleixner
2019-11-15 21:12   ` [tip: x86/iopl] " tip-bot2 for Thomas Gleixner
2019-11-13 20:42 ` [patch V3 16/20] x86/iopl: Fixup misleading comment Thomas Gleixner
2019-11-15 21:12   ` [tip: x86/iopl] " tip-bot2 for Thomas Gleixner
2019-11-13 20:42 ` [patch V3 17/20] x86/iopl: Restrict iopl() permission scope Thomas Gleixner
2019-11-14 18:13   ` Borislav Petkov
2019-11-14 18:39     ` Thomas Gleixner
2019-11-15 21:12   ` [tip: x86/iopl] " tip-bot2 for Thomas Gleixner
2019-11-13 20:42 ` [patch V3 18/20] x86/iopl: Remove legacy IOPL option Thomas Gleixner
2019-11-15 21:12   ` [tip: x86/iopl] " tip-bot2 for Thomas Gleixner
2019-11-13 20:42 ` [patch V3 19/20] x86/ioperm: Extend IOPL config to control ioperm() as well Thomas Gleixner
2019-11-15 21:12   ` [tip: x86/iopl] " tip-bot2 for Thomas Gleixner
2019-11-13 20:43 ` [patch V3 20/20] selftests/x86/iopl: Extend test to cover IOPL emulation Thomas Gleixner
2019-11-15 21:12   ` [tip: x86/iopl] " tip-bot2 for Thomas Gleixner
2019-11-14  8:43 ` [patch V3 00/20] x86/iopl: Prevent user space from using CLI/STI with iopl(3) Peter Zijlstra
2019-11-16 11:51 [tip: x86/iopl] x86/ioperm: Add bitmap sequence number tip-bot2 for Thomas Gleixner

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