From: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
To: Michael Ellerman <mpe@ellerman.id.au>, Boqun Feng <boqun.feng@gmail.com>
Cc: Will Deacon <will.deacon@arm.com>,
Peter Zijlstra <peterz@infradead.org>,
"Paul E. McKenney" <paulmck@linux.vnet.ibm.com>,
Andy Lutomirski <luto@amacapital.net>,
Dave Watson <davejwatson@fb.com>,
linux-kernel <linux-kernel@vger.kernel.org>,
linux-api <linux-api@vger.kernel.org>,
Paul Turner <pjt@google.com>,
Andrew Morton <akpm@linux-foundation.org>,
Russell King <linux@arm.linux.org.uk>,
Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@redhat.com>, "H. Peter Anvin" <hpa@zytor.com>,
Andrew Hunter <ahh@google.com>, Andi Kleen <andi@firstfloor.org>,
Chris Lameter <cl@linux.com>, Ben Maurer <bmaurer@fb.com>,
rostedt <rostedt@goodmis.org>,
Josh Triplett <josh@joshtriplett.org>,
Linus Torvalds <torvalds@linux-foundation.org>,
Catalin Marinas <catalin.marinas@arm.com>,
Michael Kerrisk <mtk.manpages@gmail.com>,
Joel Fernandes <joelaf@google.com>,
Benjamin Herrenschmidt <benh@kernel.crashing.org>,
Paul Mackerras <paulus@samba.org>,
linuxppc-dev <linuxppc-dev@lists.ozlabs.org>
Subject: Re: [PATCH 07/14] powerpc: Add support for restartable sequences
Date: Mon, 28 May 2018 03:00:19 -0400 (EDT) [thread overview]
Message-ID: <284936908.600.1527490819532.JavaMail.zimbra@efficios.com> (raw)
In-Reply-To: <87o9h5sw4e.fsf@concordia.ellerman.id.au>
----- On May 24, 2018, at 3:03 AM, Michael Ellerman mpe@ellerman.id.au wrote:
> Mathieu Desnoyers <mathieu.desnoyers@efficios.com> writes:
>> ----- On May 23, 2018, at 4:14 PM, Mathieu Desnoyers
>> mathieu.desnoyers@efficios.com wrote:
> ...
>>>
>>> Hi Boqun,
>>>
>>> I tried your patch in a ppc64 le environment, and it does not survive boot
>>> with CONFIG_DEBUG_RSEQ=y. init gets killed right away.
>
>
> Sorry this code is super gross and hard to deal with.
>
>> The following fixup gets ppc64 to work:
>>
>> --- a/arch/powerpc/kernel/entry_64.S
>> +++ b/arch/powerpc/kernel/entry_64.S
>> @@ -208,6 +208,7 @@ system_call_exit:
>> /* Check whether the syscall is issued inside a restartable sequence */
>> addi r3,r1,STACK_FRAME_OVERHEAD
>> bl rseq_syscall
>> + ld r3,RESULT(r1)
>> #endif
>> /*
>> * Disable interrupts so current_thread_info()->flags can't change,
>
> I don't think that's safe.
>
> If you look above that, we have r3, r8 and r12 all live:
>
> .Lsyscall_exit:
> std r3,RESULT(r1)
> CURRENT_THREAD_INFO(r12, r1)
>
> ld r8,_MSR(r1)
> #ifdef CONFIG_PPC_BOOK3S
> /* No MSR:RI on BookE */
> andi. r10,r8,MSR_RI
> beq- .Lunrecov_restore
> #endif
>
>
> They're all volatile across function calls:
>
> http://openpowerfoundation.org/wp-content/uploads/resources/leabi/content/dbdoclet.50655240_68174.html
>
>
> The system_call_exit symbol is actually there for kprobes and cosmetic
> purposes. The actual syscall return flow starts at .Lsyscall_exit.
>
> So I think this would work:
>
> diff --git a/arch/powerpc/kernel/entry_64.S b/arch/powerpc/kernel/entry_64.S
> index db4df061c33a..e19f377a25e0 100644
> --- a/arch/powerpc/kernel/entry_64.S
> +++ b/arch/powerpc/kernel/entry_64.S
> @@ -184,6 +184,14 @@ system_call: /* label this so stack traces look sane */
>
> .Lsyscall_exit:
> std r3,RESULT(r1)
> +
> +#ifdef CONFIG_DEBUG_RSEQ
> + /* Check whether the syscall is issued inside a restartable sequence */
> + addi r3,r1,STACK_FRAME_OVERHEAD
> + bl rseq_syscall
> + ld r3,RESULT(r1)
> +#endif
> +
> CURRENT_THREAD_INFO(r12, r1)
>
> ld r8,_MSR(r1)
>
>
> I'll try and get this series into my test setup at some point, been a
> bit busy lately :)
Yes, this was needed. I had this in my tree already, but there is still
a kernel OOPS when running the rseq selftests on ppc64 with CONFIG_DEBUG_RSEQ=y.
My current dev tree is at: https://github.com/compudj/linux-percpu-dev/tree/rseq/dev-local
So considering we are at rc7 now, should I plan to removing the powerpc bits
for merge window submission, or is there someone planning to spend time on
fixing and testing ppc integration before the merge window opens ?
Thanks,
Mathieu
>
> cheers
--
Mathieu Desnoyers
EfficiOS Inc.
http://www.efficios.com
next prev parent reply other threads:[~2018-05-28 7:00 UTC|newest]
Thread overview: 56+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-04-30 22:44 [RFC PATCH for 4.18 00/14] Restartable Sequences Mathieu Desnoyers
2018-04-30 22:44 ` [PATCH 01/14] uapi headers: Provide types_32_64.h (v2) Mathieu Desnoyers
2018-04-30 22:44 ` [PATCH 02/14] rseq: Introduce restartable sequences system call (v13) Mathieu Desnoyers
2018-05-16 16:24 ` Peter Zijlstra
2018-05-16 20:18 ` Mathieu Desnoyers
2018-04-30 22:44 ` [PATCH 03/14] arm: Add restartable sequences support Mathieu Desnoyers
2018-05-16 16:18 ` Peter Zijlstra
2018-05-16 20:13 ` Mathieu Desnoyers
2018-05-17 13:32 ` Will Deacon
2018-05-17 15:30 ` Mathieu Desnoyers
2018-05-22 18:19 ` Mathieu Desnoyers
2018-04-30 22:44 ` [PATCH 04/14] arm: Wire up restartable sequences system call Mathieu Desnoyers
2018-04-30 22:44 ` [PATCH 05/14] x86: Add support for restartable sequences (v2) Mathieu Desnoyers
2018-04-30 22:44 ` [PATCH 06/14] x86: Wire up restartable sequence system call Mathieu Desnoyers
2018-04-30 22:44 ` [PATCH 07/14] powerpc: Add support for restartable sequences Mathieu Desnoyers
2018-05-16 16:18 ` Peter Zijlstra
2018-05-16 20:13 ` Mathieu Desnoyers
2018-05-17 1:19 ` Boqun Feng
2018-05-17 7:43 ` Peter Zijlstra
2018-05-17 15:28 ` Mathieu Desnoyers
2018-05-17 23:50 ` Boqun Feng
2018-05-18 18:17 ` Mathieu Desnoyers
2018-05-20 14:08 ` Boqun Feng
2018-05-23 20:14 ` Mathieu Desnoyers
2018-05-23 20:46 ` Paul E. McKenney
2018-05-23 21:29 ` Mathieu Desnoyers
2018-05-24 1:03 ` Michael Ellerman
2018-05-28 7:00 ` Mathieu Desnoyers [this message]
2018-05-18 12:38 ` Michael Ellerman
2018-04-30 22:44 ` [PATCH 08/14] powerpc: Wire up restartable sequences system call Mathieu Desnoyers
2018-04-30 22:44 ` [PATCH 09/14] selftests: lib.mk: Introduce OVERRIDE_TARGETS Mathieu Desnoyers
2018-04-30 22:44 ` [PATCH 10/14] rseq: selftests: Provide rseq library (v5) Mathieu Desnoyers
2018-04-30 22:44 ` [PATCH 11/14] rseq: selftests: Provide basic test Mathieu Desnoyers
2018-04-30 22:44 ` [PATCH 12/14] rseq: selftests: Provide basic percpu ops test (v2) Mathieu Desnoyers
2018-04-30 22:44 ` [PATCH 13/14] rseq: selftests: Provide parametrized tests (v2) Mathieu Desnoyers
2018-04-30 22:44 ` [PATCH 14/14] rseq: selftests: Provide Makefile, scripts, gitignore (v2) Mathieu Desnoyers
2018-05-02 3:53 ` [RFC PATCH for 4.18 00/14] Restartable Sequences Daniel Colascione
2018-05-02 8:43 ` Peter Zijlstra
2018-05-02 16:03 ` Mathieu Desnoyers
2018-05-02 16:07 ` Daniel Colascione
2018-05-02 16:42 ` Steven Rostedt
2018-05-02 16:55 ` Daniel Colascione
2018-05-03 16:12 ` Mathieu Desnoyers
2018-05-03 16:22 ` Daniel Colascione
2018-05-03 18:04 ` Mathieu Desnoyers
2018-05-03 16:48 ` Joel Fernandes
2018-05-03 17:18 ` Daniel Colascione
2018-05-03 17:46 ` Joel Fernandes
2018-05-04 22:17 ` Ben Maurer
2018-05-02 17:22 ` Peter Zijlstra
2018-05-02 18:27 ` Daniel Colascione
2018-05-02 20:22 ` Peter Zijlstra
2018-05-02 20:37 ` Daniel Colascione
2018-05-03 1:15 ` Steven Rostedt
2018-05-03 8:49 ` Peter Zijlstra
2018-05-06 10:03 ` Thomas Gleixner
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