From: Ingo Molnar <mingo@kernel.org>
To: Thomas Gleixner <tglx@linutronix.de>
Cc: LKML <linux-kernel@vger.kernel.org>,
x86@kernel.org, Linus Torvalds <torvalds@linuxfoundation.org>,
Andy Lutomirski <luto@kernel.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>
Subject: [PATCH] x86/iopl: Clear up the role of the two bitmap copying fields
Date: Tue, 12 Nov 2019 09:11:53 +0100 [thread overview]
Message-ID: <20191112081153.GG100264@gmail.com> (raw)
In-Reply-To: <20191112074052.GD100264@gmail.com>
Here's another one, which makes the pointer-caching logic a bit clearer
IMO:
Firstly, it lines up the two related fields in the namespace:
x86_io_bitmap.last_bitmap => bitmap_copied_ptr
x86_io_bitmap.last_sequence => bitmap_copied_seq
It also constifies the pointer to better signal that it should never
actually be used for anything but comparison
I think the 'bitmap_copied_' ptr/seq pairing makes it more obvious, and
removing the 'last' language makes it a tiny bit clearer that this bitmap
is special because we copied its contents into the TSS.
This makes code like this a tiny bit easier to read IMHO:
+ if (tss->io_bitmap.bitmap_copied_ptr != iobm ||
+ tss->io_bitmap.bitmap_copied_seq != iobm->sequence)
I marked it RFC because you might not agree. :-)
Only build tested.
Thanks,
Ingo
---
arch/x86/include/asm/processor.h | 10 +++++-----
arch/x86/kernel/cpu/common.c | 2 +-
arch/x86/kernel/process.c | 8 ++++----
3 files changed, 10 insertions(+), 10 deletions(-)
diff --git a/arch/x86/include/asm/processor.h b/arch/x86/include/asm/processor.h
index d1f2c1eb14e9..b45ff7c1419f 100644
--- a/arch/x86/include/asm/processor.h
+++ b/arch/x86/include/asm/processor.h
@@ -367,12 +367,12 @@ struct entry_stack_page {
struct x86_io_bitmap
{
/*
- * The bitmap pointer and the sequence number of the last active
- * bitmap. last_bitmap cannot be dereferenced. It's solely for
- * comparison.
+ * The bitmap pointer and the sequence number of the last copied
+ * bitmap. bitmap_copied_ptr must not be dereferenced, it's solely
+ * for comparison.
*/
- struct io_bitmap *last_bitmap;
- u64 last_sequence;
+ const struct io_bitmap *bitmap_copied_ptr;
+ u64 bitmap_copied_seq;
/*
* Store the dirty size of the last io bitmap offender. The next
diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c
index a35a557429e7..5a74c5b11b1c 100644
--- a/arch/x86/kernel/cpu/common.c
+++ b/arch/x86/kernel/cpu/common.c
@@ -1861,7 +1861,7 @@ void cpu_init(void)
/* Initialize the TSS. */
tss_setup_ist(tss);
tss->x86_tss.io_bitmap_base = IO_BITMAP_OFFSET_INVALID;
- tss->io_bitmap.last_bitmap = NULL;
+ tss->io_bitmap.bitmap_copied_ptr = NULL;
tss->io_bitmap.bytes_max = 0;
memset(tss->io_bitmap.map_bytes, 0xff, sizeof(tss->io_bitmap.map_bytes));
set_tss_desc(cpu, &get_cpu_entry_area(cpu)->tss.x86_tss);
diff --git a/arch/x86/kernel/process.c b/arch/x86/kernel/process.c
index c4e76a540b51..ecf97855ed68 100644
--- a/arch/x86/kernel/process.c
+++ b/arch/x86/kernel/process.c
@@ -358,8 +358,8 @@ static void tss_copy_io_bitmap(struct tss_struct *tss, struct io_bitmap *iobm)
* and a pointer to the bitmap itself.
*/
tss->io_bitmap.bytes_max = iobm->bytes_max;
- tss->io_bitmap.last_sequence = iobm->sequence;
- tss->io_bitmap.last_bitmap = iobm;
+ tss->io_bitmap.bitmap_copied_seq = iobm->sequence;
+ tss->io_bitmap.bitmap_copied_ptr = iobm;
}
/**
@@ -388,8 +388,8 @@ void tss_update_io_bitmap(void)
* sequence number differs. The update time is
* accounted to the incoming task.
*/
- if (tss->io_bitmap.last_bitmap != iobm ||
- tss->io_bitmap.last_sequence != iobm->sequence)
+ if (tss->io_bitmap.bitmap_copied_ptr != iobm ||
+ tss->io_bitmap.bitmap_copied_seq != iobm->sequence)
tss_copy_io_bitmap(tss, iobm);
/* Enable the bitmap */
next prev parent reply other threads:[~2019-11-12 8:12 UTC|newest]
Thread overview: 57+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-11-11 22:03 [patch V2 00/16] x86/iopl: Prevent user space from using CLI/STI with iopl(3) Thomas Gleixner
2019-11-11 22:03 ` [patch V2 01/16] x86/ptrace: Prevent truncation of bitmap size Thomas Gleixner
2019-11-12 15:34 ` Andy Lutomirski
2019-11-11 22:03 ` [patch V2 02/16] x86/process: Unify copy_thread_tls() Thomas Gleixner
2019-11-11 22:03 ` [patch V2 03/16] x86/cpu: Unify cpu_init() Thomas Gleixner
2019-11-11 22:03 ` [patch V2 04/16] x86/tss: Fix and move VMX BUILD_BUG_ON() Thomas Gleixner
2019-11-11 22:44 ` Paolo Bonzini
2019-11-12 15:37 ` Andy Lutomirski
2019-11-11 22:03 ` [patch V2 05/16] x86/iopl: Cleanup include maze Thomas Gleixner
2019-11-12 15:37 ` Andy Lutomirski
2019-11-11 22:03 ` [patch V2 06/16] x86/io: Speedup schedule out of I/O bitmap user Thomas Gleixner
2019-11-12 16:00 ` Andy Lutomirski
2019-11-12 17:08 ` Thomas Gleixner
2019-11-11 22:03 ` [patch V2 07/16] x86/ioperm: Move iobitmap data into a struct Thomas Gleixner
2019-11-12 16:02 ` Andy Lutomirski
2019-11-12 17:08 ` Thomas Gleixner
2019-11-11 22:03 ` [patch V2 08/16] x86/ioperm: Add bitmap sequence number Thomas Gleixner
2019-11-12 9:22 ` Peter Zijlstra
2019-11-12 9:55 ` [patch V2 08/16] x86/ioperm: Add bitmap sequence numberc Thomas Gleixner
2019-11-12 16:08 ` [patch V2 08/16] x86/ioperm: Add bitmap sequence number Andy Lutomirski
2019-11-12 17:10 ` Thomas Gleixner
2019-11-11 22:03 ` [patch V2 09/16] x86/ioperm: Move TSS bitmap update to exit to user work Thomas Gleixner
2019-11-12 16:16 ` Andy Lutomirski
2019-11-12 17:20 ` Thomas Gleixner
2019-11-12 17:41 ` Andy Lutomirski
2019-11-12 17:46 ` Linus Torvalds
2019-11-13 8:30 ` Peter Zijlstra
2019-11-11 22:03 ` [patch V2 10/16] x86/ioperm: Remove bitmap if all permissions dropped Thomas Gleixner
2019-11-12 17:43 ` Andy Lutomirski
2019-11-11 22:03 ` [patch V2 11/16] x86/ioperm: Share I/O bitmap if identical Thomas Gleixner
2019-11-12 7:14 ` Ingo Molnar
2019-11-12 7:17 ` Thomas Gleixner
2019-11-12 7:52 ` Ingo Molnar
2019-11-12 9:15 ` Peter Zijlstra
2019-11-12 9:51 ` Thomas Gleixner
2019-11-14 11:02 ` David Laight
2019-11-14 12:39 ` Thomas Gleixner
2019-11-14 13:09 ` Peter Zijlstra
2019-11-14 13:22 ` David Laight
2019-11-12 18:12 ` Andy Lutomirski
2019-11-11 22:03 ` [patch V2 12/16] selftests/x86/ioperm: Extend testing so the shared bitmap is exercised Thomas Gleixner
2019-11-11 22:03 ` [patch V2 13/16] x86/iopl: Fixup misleading comment Thomas Gleixner
2019-11-12 18:14 ` Andy Lutomirski
2019-11-11 22:03 ` [patch V2 14/16] x86/iopl: Restrict iopl() permission scope Thomas Gleixner
2019-11-11 23:03 ` Thomas Gleixner
2019-11-12 6:32 ` Ingo Molnar
2019-11-12 8:42 ` Ingo Molnar
2019-11-12 10:07 ` Thomas Gleixner
2019-11-12 18:35 ` Andy Lutomirski
2019-11-11 22:03 ` [patch V2 15/16] x86/iopl: Remove legacy IOPL option Thomas Gleixner
2019-11-12 18:37 ` Andy Lutomirski
2019-11-12 19:40 ` Thomas Gleixner
2019-11-11 22:03 ` [patch V2 16/16] selftests/x86/iopl: Extend test to cover IOPL emulation Thomas Gleixner
2019-11-12 7:40 ` [PATCH] x86/iopl: Factor out IO-bitmap related TSS fields into 'struct x86_io_bitmap' Ingo Molnar
2019-11-12 7:59 ` [PATCH] x86/iopl: Harmonize 'struct io_bitmap' and 'struct x86_io_bitmap' nomenclature Ingo Molnar
2019-11-12 8:11 ` Ingo Molnar [this message]
2019-11-12 8:15 ` [PATCH] x86/iopl: Rename <asm/iobitmap.h> to <asm/io_bitmap.h> Ingo Molnar
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