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Date: Sat, 16 Nov 2019 11:51:23 -0000
From: "tip-bot2 for Thomas Gleixner" <tip-bot2@...utronix.de>
To: linux-tip-commits@...r.kernel.org
Cc: Linus Torvalds <torvalds@...ux-foundation.org>,
Thomas Gleixner <tglx@...utronix.de>,
Ingo Molnar <mingo@...nel.org>, Borislav Petkov <bp@...en8.de>,
linux-kernel@...r.kernel.org
Subject: [tip: x86/iopl] x86/ioperm: Add bitmap sequence number
The following commit has been merged into the x86/iopl branch of tip:
Commit-ID: 060aa16fdb7c5078a4159a76e5dc87d6a493af9b
Gitweb: https://git.kernel.org/tip/060aa16fdb7c5078a4159a76e5dc87d6a493af9b
Author: Thomas Gleixner <tglx@...utronix.de>
AuthorDate: Mon, 11 Nov 2019 23:03:22 +01:00
Committer: Thomas Gleixner <tglx@...utronix.de>
CommitterDate: Sat, 16 Nov 2019 11:24:02 +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@...ux-foundation.org>
Signed-off-by: Thomas Gleixner <tglx@...utronix.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 1504fd2..7c49be9 100644
--- a/arch/x86/kernel/process.c
+++ b/arch/x86/kernel/process.c
@@ -360,6 +360,28 @@ 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)
{
@@ -369,18 +391,14 @@ 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;
/*
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