From: Ingo Molnar <mingo@kernel.org>
To: Andy Lutomirski <luto@kernel.org>
Cc: x86@kernel.org, LKML <linux-kernel@vger.kernel.org>,
Linus Torvalds <torvalds@linux-foundation.org>,
Kernel Hardening <kernel-hardening@lists.openwall.com>,
Borislav Petkov <bp@alien8.de>
Subject: [kernel-hardening] Re: [PATCH 2/3] x86/asm: Move 'status' from thread_struct to thread_info
Date: Sun, 28 Jan 2018 20:02:43 +0100 [thread overview]
Message-ID: <20180128190243.gp3ner27uhsnnjpb@gmail.com> (raw)
In-Reply-To: <03148bcc1b217100e6e8ecf6a5468c45cf4304b6.1517164461.git.luto@kernel.org>
* Andy Lutomirski <luto@kernel.org> wrote:
> The TS_COMPAT bit is very hot and is accessed from code paths that
> mostly also touch thread_info::flags. Move it into struct
> thread_info to improve cache locality.
>
> The only reason it was in thread_struct is that there was a brief
> period during which we didn't allow arch-specific fields in struct
> thread_info.
>
> Linus suggested further changing:
>
> ti->status &= ~(TS_COMPAT|TS_I386_REGS_POKED);
>
> to:
>
> if (unlikely(ti->status & (TS_COMPAT|TS_I386_REGS_POKED)))
> ti->status &= ~(TS_COMPAT|TS_I386_REGS_POKED);
>
> on the theory that frequently dirtying the cacheline even in pure
> 64-bit code that never needs to modify status hurts performance.
> That could be a reasonable followup patch, but I suspect it matters
> less on top of this patch.
>
> Suggested-by: Linus Torvalds <torvalds@linux-foundation.org>
> Signed-off-by: Andy Lutomirski <luto@kernel.org>
> ---
> arch/x86/entry/common.c | 4 ++--
> arch/x86/include/asm/processor.h | 2 --
> arch/x86/include/asm/syscall.h | 6 +++---
> arch/x86/include/asm/thread_info.h | 3 ++-
> arch/x86/kernel/process_64.c | 4 ++--
> arch/x86/kernel/ptrace.c | 2 +-
> arch/x86/kernel/signal.c | 2 +-
> 7 files changed, 11 insertions(+), 12 deletions(-)
Reviewed-by: Ingo Molnar <mingo@kernel.org>
Thanks,
Ingo
next prev parent reply other threads:[~2018-01-28 19:02 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-01-28 18:38 [kernel-hardening] [PATCH 0/3] x86/pti-ish syscall cleanups Andy Lutomirski
2018-01-28 18:38 ` [kernel-hardening] [PATCH 1/3] x86/entry/64: Remove the SYSCALL64 fast path Andy Lutomirski
2018-01-28 19:00 ` [kernel-hardening] " Ingo Molnar
2018-01-28 18:38 ` [kernel-hardening] [PATCH 2/3] x86/asm: Move 'status' from thread_struct to thread_info Andy Lutomirski
2018-01-28 19:02 ` Ingo Molnar [this message]
2018-01-28 19:19 ` [kernel-hardening] " Linus Torvalds
2018-01-28 18:38 ` [kernel-hardening] [PATCH 3/3] syscalls: Add a bit of documentation to __SYSCALL_DEFINE Andy Lutomirski
2018-01-28 19:15 ` [kernel-hardening] " Linus Torvalds
2018-01-28 20:21 ` Al Viro
2018-01-28 20:42 ` Linus Torvalds
2018-01-28 22:50 ` Al Viro
2018-01-29 6:22 ` Al Viro
2018-01-28 19:21 ` Ingo Molnar
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