From: hpa@zytor.com
To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>,
Nadav Amit <namit@vmware.com>, Andy Lutomirski <luto@kernel.org>,
Peter Zijlstra <peterz@infradead.org>,
the arch/x86 maintainers <x86@kernel.org>,
Linux List Kernel Mailing <linux-kernel@vger.kernel.org>,
Ard Biesheuvel <ard.biesheuvel@linaro.org>,
Steven Rostedt <rostedt@goodmis.org>,
Ingo Molnar <mingo@kernel.org>,
Thomas Gleixner <tglx@linutronix.de>,
Masami Hiramatsu <mhiramat@kernel.org>,
Jason Baron <jbaron@akamai.com>, Jiri Kosina <jkosina@suse.cz>,
David Laight <David.Laight@aculab.com>,
Borislav Petkov <bp@alien8.de>, Julia Cartwright <julia@ni.com>,
Jessica Yu <jeyu@kernel.org>,
Rasmus Villemoes <linux@rasmusvillemoes.dk>,
Edward Cree <ecree@solarflare.com>,
Daniel Bristot de Oliveira <bristot@redhat.com>
Subject: Re: [PATCH v3 0/6] Static calls
Date: Sat, 12 Jan 2019 16:36:38 -0800 [thread overview]
Message-ID: <E2076BDA-FED4-449F-805F-F255755C78A2@zytor.com> (raw)
In-Reply-To: <CAHk-=wgQR1RfjA9V70cL-vTrhYBF9FWhPRaZahQuDaSazL+kAQ@mail.gmail.com>
On January 11, 2019 11:34:34 AM PST, Linus Torvalds <torvalds@linux-foundation.org> wrote:
>On Fri, Jan 11, 2019 at 11:24 AM <hpa@zytor.com> wrote:
>>
>> I still don't see why can't simply spin in the #BP handler until the
>patch is complete.
>
>So here's at least one problem:
>
>text_poke_bp()
> text_poke(addr, &int3, sizeof(int3));
> *interrupt*
> interrupt has a static call
> *BP*
> poke_int3_handler
> *BOOM*
>
>Note how at BOOM we cannot just spin (or return) to wait for the
>'int3' to be switched back. Becuase it never will. Because we are
>interrupting the thing that would do that switch-back.
>
>So we'd have to do the 'text_poke_bp()' sequence with interrupts
>disabled. Which we can't do right now at least, because part of that
>sequence involves that on_each_cpu(do_sync_core) thing, which needs
>interrupts enabled.
>
>See?
>
>Or am I missing something?
>
> Linus
Ok, I was thinking far more about spinning with an IRET and letting the exception be delivered. Patching with interrupts disabled have other problems...
--
Sent from my Android device with K-9 Mail. Please excuse my brevity.
next prev parent reply other threads:[~2019-01-13 0:37 UTC|newest]
Thread overview: 90+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-01-09 22:59 [PATCH v3 0/6] Static calls Josh Poimboeuf
2019-01-09 22:59 ` [PATCH v3 1/6] compiler.h: Make __ADDRESSABLE() symbol truly unique Josh Poimboeuf
2019-01-09 22:59 ` [PATCH v3 2/6] static_call: Add basic static call infrastructure Josh Poimboeuf
2019-01-10 14:03 ` Edward Cree
2019-01-10 18:37 ` Josh Poimboeuf
2019-01-09 22:59 ` [PATCH v3 3/6] x86/static_call: Add out-of-line static call implementation Josh Poimboeuf
2019-01-10 0:16 ` Nadav Amit
2019-01-10 16:28 ` Josh Poimboeuf
2019-01-09 22:59 ` [PATCH v3 4/6] static_call: Add inline static call infrastructure Josh Poimboeuf
2019-01-09 22:59 ` [PATCH v3 5/6] x86/alternative: Use a single access in text_poke() where possible Josh Poimboeuf
2019-01-10 9:32 ` Nadav Amit
2019-01-10 17:20 ` Josh Poimboeuf
2019-01-10 17:29 ` Nadav Amit
2019-01-10 17:32 ` Steven Rostedt
2019-01-10 17:42 ` Sean Christopherson
2019-01-10 17:57 ` Steven Rostedt
2019-01-10 18:04 ` Sean Christopherson
2019-01-10 18:21 ` Josh Poimboeuf
2019-01-10 18:24 ` Steven Rostedt
2019-01-11 12:10 ` Alexandre Chartre
2019-01-11 15:28 ` Josh Poimboeuf
2019-01-11 16:46 ` Alexandre Chartre
2019-01-11 16:57 ` Josh Poimboeuf
2019-01-11 17:41 ` Jason Baron
2019-01-11 17:54 ` Nadav Amit
2019-01-15 11:10 ` Alexandre Chartre
2019-01-15 16:19 ` Steven Rostedt
2019-01-15 16:45 ` Alexandre Chartre
2019-01-11 0:59 ` hpa
2019-01-11 1:34 ` Sean Christopherson
2019-01-11 8:13 ` hpa
2019-01-09 22:59 ` [PATCH v3 6/6] x86/static_call: Add inline static call implementation for x86-64 Josh Poimboeuf
2019-01-10 1:21 ` [PATCH v3 0/6] Static calls Nadav Amit
2019-01-10 16:44 ` Josh Poimboeuf
2019-01-10 17:32 ` Nadav Amit
2019-01-10 18:18 ` Josh Poimboeuf
2019-01-10 19:45 ` Nadav Amit
2019-01-10 20:32 ` Josh Poimboeuf
2019-01-10 20:48 ` Nadav Amit
2019-01-10 20:57 ` Josh Poimboeuf
2019-01-10 21:47 ` Nadav Amit
2019-01-10 17:31 ` Linus Torvalds
2019-01-10 20:51 ` H. Peter Anvin
2019-01-10 20:30 ` Peter Zijlstra
2019-01-10 20:52 ` Josh Poimboeuf
2019-01-10 23:02 ` Linus Torvalds
2019-01-11 0:56 ` Andy Lutomirski
2019-01-11 1:47 ` Nadav Amit
2019-01-11 15:15 ` Josh Poimboeuf
2019-01-11 15:48 ` Nadav Amit
2019-01-11 16:07 ` Josh Poimboeuf
2019-01-11 17:23 ` Nadav Amit
2019-01-11 19:03 ` Linus Torvalds
2019-01-11 19:17 ` Nadav Amit
2019-01-11 19:23 ` hpa
2019-01-11 19:33 ` Nadav Amit
2019-01-11 19:34 ` Linus Torvalds
2019-01-13 0:34 ` hpa
2019-01-13 0:36 ` hpa [this message]
2019-01-11 19:39 ` Jiri Kosina
2019-01-14 2:31 ` H. Peter Anvin
2019-01-14 2:40 ` H. Peter Anvin
2019-01-14 20:11 ` Andy Lutomirski
2019-01-14 22:00 ` H. Peter Anvin
2019-01-14 22:54 ` H. Peter Anvin
2019-01-15 3:05 ` Andy Lutomirski
2019-01-15 5:01 ` H. Peter Anvin
2019-01-15 5:37 ` H. Peter Anvin
2019-01-14 23:27 ` Andy Lutomirski
2019-01-14 23:51 ` Nadav Amit
2019-01-15 2:28 ` hpa
2019-01-11 20:04 ` Josh Poimboeuf
2019-01-11 20:12 ` Linus Torvalds
2019-01-11 20:31 ` Josh Poimboeuf
2019-01-11 20:46 ` Linus Torvalds
2019-01-11 21:05 ` Andy Lutomirski
2019-01-11 21:10 ` Linus Torvalds
2019-01-11 21:32 ` Josh Poimboeuf
2019-01-14 12:28 ` Peter Zijlstra
2019-01-11 21:22 ` Josh Poimboeuf
2019-01-11 21:23 ` Josh Poimboeuf
2019-01-11 21:25 ` Josh Poimboeuf
2019-01-11 21:36 ` Nadav Amit
2019-01-11 21:41 ` Josh Poimboeuf
2019-01-11 21:55 ` Steven Rostedt
2019-01-11 21:59 ` Nadav Amit
2019-01-11 21:56 ` Nadav Amit
2019-01-12 23:54 ` Andy Lutomirski
2020-02-17 21:10 ` Jann Horn
2020-02-17 21:57 ` Steven Rostedt
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