From: Linus Torvalds <torvalds@linux-foundation.org>
To: Andy Lutomirski <luto@amacapital.net>
Cc: Peter Zijlstra <peterz@infradead.org>,
Thomas Gleixner <tglx@linutronix.de>,
Borislav Petkov <bp@alien8.de>, Ingo Molnar <mingo@kernel.org>,
Steven Rostedt <rostedt@goodmis.org>,
Andrew Lutomirski <luto@kernel.org>, Peter Anvin <hpa@zytor.com>,
Dave Hansen <dave.hansen@linux.intel.com>,
Juergen Gross <jgross@suse.com>,
Linux List Kernel Mailing <linux-kernel@vger.kernel.org>,
He Zhe <zhe.he@windriver.com>,
Joel Fernandes <joel@joelfernandes.org>,
devel@etsukata.com
Subject: Re: [PATCH v2 5/7] x86/mm, tracing: Fix CR2 corruption
Date: Fri, 5 Jul 2019 12:27:49 +0900 [thread overview]
Message-ID: <CAHk-=whzQDR+hjhontUhsCbQOryU7VZ9K79EVjL2KCduZWDc1Q@mail.gmail.com> (raw)
In-Reply-To: <41D6F2E2-C4CF-41DF-A843-FCBD03B7BEEB@amacapital.net>
On Fri, Jul 5, 2019 at 12:16 PM Andy Lutomirski <luto@amacapital.net> wrote:
>
> If nothing else, MOV to CR2 is architecturally serializing, so, unless there’s some fancy unwinding involved, this will be quite slow.
That's why the NMI code does this:
if (unlikely(this_cpu_read(nmi_cr2) != read_cr2()))
write_cr2(this_cpu_read(nmi_cr2));
so that it normally only does a read. Only if you actually took a page
fault will it restore cr2 to the old value (and if you took a page
fault the performance issues will be _there_, not in the "restore cr2"
part)
Linus
next prev parent reply other threads:[~2019-07-05 3:28 UTC|newest]
Thread overview: 42+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-07-04 19:55 [PATCH v2 0/7] Tracing vs CR2 (and cleanups) Peter Zijlstra
2019-07-04 19:55 ` [PATCH v2 1/7] x86/paravirt: Make read_cr2() CALLEE_SAVE Peter Zijlstra
2019-07-04 21:49 ` Andy Lutomirski
2019-07-10 19:53 ` Steven Rostedt
2019-07-04 19:55 ` [PATCH v2 2/7] x86/entry/32: Simplify common_exception Peter Zijlstra
2019-07-04 21:51 ` Andy Lutomirski
2019-07-10 20:11 ` Steven Rostedt
2019-07-10 20:14 ` Peter Zijlstra
2019-07-04 19:55 ` [PATCH v2 3/7] x86/entry/64: Simplify idtentry a little Peter Zijlstra
2019-07-04 21:54 ` Andy Lutomirski
2019-07-10 20:23 ` Steven Rostedt
2019-07-04 19:55 ` [PATCH v2 4/7] x86/entry/64: Update comments and sanity tests for create_gap Peter Zijlstra
2019-07-04 21:55 ` Andy Lutomirski
2019-07-10 20:24 ` Steven Rostedt
2019-07-04 19:56 ` [PATCH v2 5/7] x86/mm, tracing: Fix CR2 corruption Peter Zijlstra
2019-07-05 2:18 ` Linus Torvalds
2019-07-05 3:16 ` Andy Lutomirski
2019-07-05 3:27 ` Linus Torvalds [this message]
2019-07-05 13:49 ` Peter Zijlstra
2019-07-06 21:41 ` Linus Torvalds
2019-07-06 22:27 ` Steven Rostedt
2019-07-06 22:41 ` Linus Torvalds
2019-07-07 0:08 ` Linus Torvalds
2019-07-07 0:36 ` Andy Lutomirski
2019-07-06 23:50 ` Andy Lutomirski
2019-07-07 3:44 ` Eiichi Tsukata
2019-07-06 11:07 ` Eiichi Tsukata
2019-07-08 7:48 ` Peter Zijlstra
2019-07-08 8:58 ` Eiichi Tsukata
2019-07-08 9:42 ` Eiichi Tsukata
2019-07-09 5:17 ` Eiichi Tsukata
2019-07-07 15:10 ` Andy Lutomirski
2019-07-07 15:11 ` Andy Lutomirski
2019-07-07 18:17 ` Linus Torvalds
2019-07-10 20:27 ` Steven Rostedt
2019-07-11 6:45 ` Greg Kroah-Hartman
2019-07-11 12:12 ` Sasha Levin
2019-07-11 12:21 ` Peter Zijlstra
2019-07-04 19:56 ` [PATCH v2 6/7] x86/entry/64: Remove TRACE_IRQS_*_DEBUG Peter Zijlstra
2019-07-11 3:24 ` Steven Rostedt
2019-07-11 8:05 ` Peter Zijlstra
2019-07-04 19:56 ` [RFC][PATCH v2 7/7] x86/entry/64: Pull bits into C Peter Zijlstra
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