From: Nicolai Stange <nstange@suse.de>
To: Steven Rostedt <rostedt@goodmis.org>
Cc: Andy Lutomirski <luto@amacapital.net>,
Nicolai Stange <nstange@suse.de>,
Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
"H. Peter Anvin" <hpa@zytor.com>,
x86@kernel.org, Josh Poimboeuf <jpoimboe@redhat.com>,
Jiri Kosina <jikos@kernel.org>, Miroslav Benes <mbenes@suse.cz>,
Petr Mladek <pmladek@suse.com>,
Joe Lawrence <joe.lawrence@redhat.com>,
Shuah Khan <shuah@kernel.org>,
Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>,
Tim Chen <tim.c.chen@linux.intel.com>,
Sebastian Andrzej Siewior <bigeasy@linutronix.de>,
Mimi Zohar <zohar@linux.ibm.com>, Juergen Gross <jgross@suse.com>,
Nick Desaulniers <ndesaulniers@google.com>,
Nayna Jain <nayna@linux.ibm.com>,
Masahiro Yamada <yamada.masahiro@socionext.com>,
Andy Lutomirski <luto@kernel.org>, Joerg Roedel <jroedel@suse.de>,
linux-kernel@vger.kernel.org, live-patching@vger.kernel.org,
linux-kselftest@vger.kernel.org
Subject: Re: [PATCH 1/4] x86/thread_info: introduce ->ftrace_int3_stack member
Date: Sun, 28 Apr 2019 23:22:54 +0200 [thread overview]
Message-ID: <87k1fdygcx.fsf@suse.de> (raw)
In-Reply-To: <20190428135143.09d35bb6@oasis.local.home> (Steven Rostedt's message of "Sun, 28 Apr 2019 13:51:43 -0400")
Steven Rostedt <rostedt@goodmis.org> writes:
> On Sun, 28 Apr 2019 10:41:10 -0700
> Andy Lutomirski <luto@amacapital.net> wrote:
>
>
>> > Note that at any given point
>> > in time, there can be at most four such call insn emulations pending:
>> > namely at most one per "process", "irq", "softirq" and "nmi" context.
>> >
>>
>> That’s quite an assumption. I think your list should also contain
>> exception, exceptions nested inside that exception, and machine
>> check, at the very least. I’m also wondering why irq and softirq are
>> treated separately.
You're right, I missed the machine check case.
> 4 has usually been the context count we choose. But I guess in theory,
> if we get exceptions then I could potentially be more.
After having seen the static_call discussion, I'm in no way defending
this limited approach here, but out of curiosity: can the code between
the push onto the stack from ftrace_int3_handler() and the subsequent
pop from the stub actually trigger an (non-#MC) exception? There's an
iret inbetween, but that can fault only when returning to user space,
correct?
> As for irq vs softirq, an interrupt can preempt a softirq. Interrupts
> are enabled while softirqs are running. When sofirqs run, softirqs are
> disabled to prevent nested softirqs. But interrupts are enabled again,
> and another interrupt may come in while a softirq is executing.
>
Thanks,
Nicolai
--
SUSE Linux GmbH, GF: Felix Imendörffer, Jane Smithard, Graham Norton,
HRB 21284 (AG Nürnberg)
next prev parent reply other threads:[~2019-04-28 21:23 UTC|newest]
Thread overview: 64+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-04-27 10:06 [PATCH 0/4] x86/ftrace: make ftrace_int3_handler() not to skip fops invocation Nicolai Stange
2019-04-27 10:06 ` [PATCH 1/4] x86/thread_info: introduce ->ftrace_int3_stack member Nicolai Stange
2019-04-28 17:41 ` Andy Lutomirski
2019-04-28 17:51 ` Steven Rostedt
2019-04-28 18:08 ` Andy Lutomirski
2019-04-28 19:43 ` Steven Rostedt
2019-04-28 20:56 ` Andy Lutomirski
2019-04-28 21:22 ` Nicolai Stange [this message]
2019-04-28 23:27 ` Andy Lutomirski
2019-04-27 10:06 ` [PATCH 2/4] ftrace: drop 'static' qualifier from ftrace_ops_list_func() Nicolai Stange
2019-04-27 10:06 ` [PATCH 3/4] x86/ftrace: make ftrace_int3_handler() not to skip fops invocation Nicolai Stange
2019-04-27 10:26 ` Peter Zijlstra
2019-04-28 17:38 ` Steven Rostedt
2019-04-29 18:06 ` Linus Torvalds
2019-04-29 18:22 ` Linus Torvalds
2019-04-29 18:42 ` Andy Lutomirski
[not found] ` <CAHk-=whtt4K2f0KPtG-4Pykh3FK8UBOjD8jhXCUKB5nWDj_YRA@mail.gmail.com>
2019-04-29 18:56 ` Andy Lutomirski
[not found] ` <CAHk-=wgewK4eFhF3=0RNtk1KQjMANFH6oDE=8m=84RExn2gxhw@mail.gmail.com>
[not found] ` <CAHk-=whay7eN6+2gZjY-ybRbkbcqAmgrLwwszzHx8ws3c=S-MA@mail.gmail.com>
2019-04-29 19:24 ` Andy Lutomirski
2019-04-29 20:07 ` Linus Torvalds
2019-04-30 13:56 ` Peter Zijlstra
2019-04-30 16:06 ` Linus Torvalds
2019-04-30 16:33 ` Andy Lutomirski
2019-04-30 17:03 ` Steven Rostedt
2019-04-30 17:20 ` Steven Rostedt
2019-04-30 17:49 ` [RFC][PATCH] ftrace/x86: Emulate call function while updating in breakpoint handler Steven Rostedt
2019-04-30 18:33 ` Linus Torvalds
2019-04-30 19:00 ` Steven Rostedt
2019-04-30 21:08 ` Steven Rostedt
2019-05-01 13:11 ` Peter Zijlstra
2019-05-01 18:58 ` Steven Rostedt
2019-05-01 19:03 ` Peter Zijlstra
2019-05-01 19:03 ` Linus Torvalds
2019-05-01 19:13 ` Peter Zijlstra
2019-05-01 19:13 ` Steven Rostedt
2019-05-01 19:33 ` Jiri Kosina
2019-05-01 19:41 ` Peter Zijlstra
2019-04-30 21:53 ` [RFC][PATCH v2] " Steven Rostedt
2019-05-01 1:35 ` Steven Rostedt
2019-05-01 1:58 ` Linus Torvalds
2019-05-01 8:26 ` Nicolai Stange
2019-05-01 13:22 ` Steven Rostedt
2019-04-29 20:16 ` [PATCH 3/4] x86/ftrace: make ftrace_int3_handler() not to skip fops invocation Linus Torvalds
2019-04-29 22:08 ` Sean Christopherson
2019-04-29 22:22 ` Linus Torvalds
2019-04-30 0:08 ` Sean Christopherson
2019-04-30 0:45 ` Sean Christopherson
2019-04-30 2:26 ` Linus Torvalds
2019-04-30 10:40 ` Peter Zijlstra
2019-04-30 11:17 ` Jiri Kosina
2019-04-29 22:06 ` Linus Torvalds
2019-04-30 11:18 ` Peter Zijlstra
2019-04-29 18:52 ` Steven Rostedt
[not found] ` <CAHk-=wjm93jLtVxTX4HZs6K4k1Wqh3ujjmapqaYtcibVk_YnzQ@mail.gmail.com>
2019-04-29 19:07 ` Steven Rostedt
2019-04-29 20:06 ` Linus Torvalds
2019-04-29 20:20 ` Linus Torvalds
2019-04-29 20:30 ` Steven Rostedt
2019-04-29 21:38 ` Linus Torvalds
2019-04-29 22:07 ` Steven Rostedt
2019-04-30 9:24 ` Nicolai Stange
2019-04-30 10:46 ` Peter Zijlstra
2019-04-30 13:44 ` Steven Rostedt
2019-04-30 14:20 ` Peter Zijlstra
2019-04-30 14:36 ` Steven Rostedt
2019-04-27 10:06 ` [PATCH 4/4] selftests/livepatch: add "ftrace a live patched function" test Nicolai Stange
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=87k1fdygcx.fsf@suse.de \
--to=nstange@suse.de \
--cc=bigeasy@linutronix.de \
--cc=bp@alien8.de \
--cc=hpa@zytor.com \
--cc=jgross@suse.com \
--cc=jikos@kernel.org \
--cc=joe.lawrence@redhat.com \
--cc=jpoimboe@redhat.com \
--cc=jroedel@suse.de \
--cc=konrad.wilk@oracle.com \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-kselftest@vger.kernel.org \
--cc=live-patching@vger.kernel.org \
--cc=luto@amacapital.net \
--cc=luto@kernel.org \
--cc=mbenes@suse.cz \
--cc=mingo@redhat.com \
--cc=nayna@linux.ibm.com \
--cc=ndesaulniers@google.com \
--cc=pmladek@suse.com \
--cc=rostedt@goodmis.org \
--cc=shuah@kernel.org \
--cc=tglx@linutronix.de \
--cc=tim.c.chen@linux.intel.com \
--cc=x86@kernel.org \
--cc=yamada.masahiro@socionext.com \
--cc=zohar@linux.ibm.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).