From: Thomas Gleixner <tglx@linutronix.de>
To: LKML <linux-kernel@vger.kernel.org>
Cc: x86@kernel.org, Andy Lutomirski <luto@kernel.org>,
Linus Torvalds <torvalds@linuxfoundation.org>,
Stephen Hemminger <stephen@networkplumber.org>,
Willy Tarreau <w@1wt.eu>, Juergen Gross <jgross@suse.com>,
Sean Christopherson <sean.j.christopherson@intel.com>,
"H. Peter Anvin" <hpa@zytor.com>,
Linus Torvalds <torvalds@linux-foundation.org>
Subject: [patch V3 11/20] x86/ioperm: Add bitmap sequence number
Date: Wed, 13 Nov 2019 21:42:51 +0100 [thread overview]
Message-ID: <20191113210104.790774205@linutronix.de> (raw)
In-Reply-To: 20191113204240.767922595@linutronix.de
From: Thomas Gleixner <tglx@linutronix.de>
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>
---
V3: Remove the pointer comparison (Peter, Andy)
V2: New patch
---
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(-)
--- 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];
--- 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
--- 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);
--- 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, uns
/* 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
--- 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(stru
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;
/*
next prev parent reply other threads:[~2019-11-13 21:03 UTC|newest]
Thread overview: 52+ 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 ` Thomas Gleixner [this message]
2019-11-15 21:12 ` [tip: x86/iopl] x86/ioperm: Add bitmap sequence number tip-bot2 for Thomas Gleixner
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
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