From: Will Deacon <will.deacon@arm.com>
To: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Stephen Rothwell <sfr@canb.auug.org.au>,
Thomas Gleixner <tglx@linutronix.de>, Ingo Molnar <mingo@elte.hu>,
"H. Peter Anvin" <hpa@zytor.com>,
Peter Zijlstra <peterz@infradead.org>,
Linux-Next Mailing List <linux-next@vger.kernel.org>,
linux-kernel <linux-kernel@vger.kernel.org>
Subject: Re: linux-next: manual merge of the tip tree with Linus' tree
Date: Tue, 6 Feb 2018 13:55:12 +0000 [thread overview]
Message-ID: <20180206135512.GB22740@arm.com> (raw)
In-Reply-To: <750091485.16756.1517921554396.JavaMail.zimbra@efficios.com>
On Tue, Feb 06, 2018 at 12:52:34PM +0000, Mathieu Desnoyers wrote:
> ----- On Feb 5, 2018, at 7:40 PM, Stephen Rothwell sfr@canb.auug.org.au wrote:
>
> > Hi all,
> >
> > Today's linux-next merge of the tip tree got a conflict in:
> >
> > arch/arm64/kernel/entry.S
> >
> > between commit:
> >
> > 4bf3286d29f3 ("arm64: entry: Hook up entry trampoline to exception vectors")
> >
> > from Linus' tree and commit:
> >
> > f1e3a12b6543 ("membarrier/arm64: Provide core serializing command")
> >
> > from the tip tree.
> >
> > I fixed it up (probably not completely - see below) and can carry the
> > fix as necessary. This is now fixed as far as linux-next is concerned,
> > but any non trivial conflicts should be mentioned to your upstream
> > maintainer when your tree is submitted for merging. You may also want
> > to consider cooperating with the maintainer of the conflicting tree to
> > minimise any particularly complex conflicts.
>
> The change introduced by 4bf3286d29 "arm64: entry: Hook up entry trampoline
> to exception vectors" adds a trampoline as mechanism for return:
>
> - eret // return to kernel
> +
> +#ifndef CONFIG_UNMAP_KERNEL_AT_EL0
> + eret
> +#else
> + .if \el == 0
> + bne 4f
> + msr far_el1, x30
> + tramp_alias x30, tramp_exit_native
> + br x30
> +4:
> + tramp_alias x30, tramp_exit_compat
> + br x30
> + .else
> + eret
> + .endif
> +#endif
>
> Which means that with CONFIG_UNMAP_KERNEL_AT_EL0, for return to EL0,
> the eret is in the trampoline:
>
> .macro tramp_exit, regsize = 64
> adr x30, tramp_vectors
> msr vbar_el1, x30
> tramp_unmap_kernel x30
> .if \regsize == 64
> mrs x30, far_el1
> .endif
> eret
> .endm
>
> ENTRY(tramp_exit_native)
> tramp_exit
> END(tramp_exit_native)
>
> ENTRY(tramp_exit_compat)
> tramp_exit 32
> END(tramp_exit_compat)
>
>
> One approach I would consider for this is to duplicate this
> comment and add it just above the "eret" instruction within the
> macro:
>
> /*
> * ARCH_HAS_MEMBARRIER_SYNC_CORE rely on eret context synchronization
> * when returning from IPI handler, and when returning to user-space.
> */
>
> Or perhaps Will has something else in mind ?
To be honest with you, I'd just drop the comment entirely. entry.S is
terrifying these days and nobody should have to go in there to understand
why we select ARCH_HAS_MEMBARRIER_SYNC_CORE. If you really feel a justification
is needed, I'd be happy with a line in the Kconfig file.
Will
next prev parent reply other threads:[~2018-02-06 13:55 UTC|newest]
Thread overview: 122+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-02-06 0:40 linux-next: manual merge of the tip tree with Linus' tree Stephen Rothwell
2018-02-06 12:52 ` Mathieu Desnoyers
2018-02-06 13:55 ` Will Deacon [this message]
2018-02-06 14:06 ` Mathieu Desnoyers
2018-02-06 14:11 ` Will Deacon
2018-02-06 17:05 ` Mathieu Desnoyers
2018-02-06 17:21 ` Will Deacon
2018-02-08 7:03 ` Ingo Molnar
2018-02-08 18:56 ` Will Deacon
2018-02-08 19:04 ` Mathieu Desnoyers
2018-02-09 18:25 ` Will Deacon
2018-02-09 20:35 ` Mathieu Desnoyers
-- strict thread matches above, loose matches on Subject: below --
2024-02-08 1:30 Stephen Rothwell
2023-10-16 1:38 Stephen Rothwell
2023-08-09 2:15 Stephen Rothwell
2023-02-15 1:08 Stephen Rothwell
2023-02-15 11:15 ` Ingo Molnar
2022-07-13 5:08 Stephen Rothwell
2022-05-09 3:59 Stephen Rothwell
2022-01-04 2:45 Stephen Rothwell
2021-10-11 2:21 Stephen Rothwell
2021-10-11 20:48 ` Borislav Petkov
2020-11-06 2:39 Stephen Rothwell
2020-11-06 2:46 ` Steven Rostedt
2020-08-12 1:21 Stephen Rothwell
2020-06-11 1:00 Stephen Rothwell
2020-06-11 0:52 Stephen Rothwell
2020-06-11 10:43 ` Thomas Gleixner
2020-06-11 11:03 ` Stephen Rothwell
2020-06-10 1:49 Stephen Rothwell
2020-06-10 1:42 Stephen Rothwell
2020-05-18 5:10 Stephen Rothwell
2020-05-18 7:12 ` Borislav Petkov
2020-01-06 2:17 Stephen Rothwell
2020-01-06 6:53 ` Ingo Molnar
2019-12-20 1:53 Stephen Rothwell
2019-12-16 2:43 Stephen Rothwell
2019-12-03 2:10 Stephen Rothwell
2019-12-03 6:57 ` Ingo Molnar
2019-12-03 8:56 ` Stephen Rothwell
2019-09-02 7:31 Stephen Rothwell
2019-09-02 18:07 ` Ingo Molnar
2019-07-29 2:00 Stephen Rothwell
2019-03-06 5:53 Stephen Rothwell
2018-10-12 2:14 Stephen Rothwell
2018-10-12 2:18 ` Kees Cook
2018-10-12 10:47 ` Ingo Molnar
2018-10-12 18:56 ` Kees Cook
2018-06-07 1:53 Stephen Rothwell
2018-02-12 1:27 Stephen Rothwell
2018-02-12 7:19 ` Ingo Molnar
2018-02-06 0:54 Stephen Rothwell
2018-02-06 9:14 ` Peter Zijlstra
2018-02-06 0:44 Stephen Rothwell
2017-11-10 1:27 Stephen Rothwell
2017-05-22 3:27 Stephen Rothwell
2017-05-22 8:32 ` Mark Rutland
2017-05-22 21:44 ` Stephen Rothwell
2017-05-23 8:37 ` Mark Rutland
2016-02-03 0:09 Stephen Rothwell
2016-02-03 0:32 ` Toshi Kani
2015-09-18 1:12 Stephen Rothwell
2015-08-17 5:57 Stephen Rothwell
2015-07-06 0:08 Stephen Rothwell
2015-07-06 7:49 ` Paolo Bonzini
2015-07-06 21:34 ` Stephen Rothwell
2014-05-21 4:12 Stephen Rothwell
2014-05-21 4:24 ` H. Peter Anvin
2014-05-21 6:01 ` Ingo Molnar
2014-05-21 6:02 ` H. Peter Anvin
2014-05-21 6:05 ` Ingo Molnar
2014-05-21 6:10 ` Ingo Molnar
2014-05-21 4:12 Stephen Rothwell
2014-03-21 4:23 Stephen Rothwell
2014-03-21 8:47 ` Srivatsa S. Bhat
2014-02-18 3:09 Stephen Rothwell
2014-02-18 8:06 ` Hans-Christian Egtvedt
2014-02-18 14:15 ` Chen Gang
2014-01-30 1:42 Stephen Rothwell
2014-01-30 1:49 ` Andi Kleen
2014-01-30 1:58 ` Stephen Rothwell
2014-01-30 2:05 ` Andi Kleen
2014-01-28 0:43 Stephen Rothwell
2014-01-17 3:30 Stephen Rothwell
2014-01-17 17:27 ` Sören Brinkmann
2013-12-16 3:18 Stephen Rothwell
2013-09-04 4:24 Stephen Rothwell
2013-07-09 4:36 Stephen Rothwell
2012-12-03 4:19 Stephen Rothwell
2012-10-16 1:00 Stephen Rothwell
2012-10-21 16:29 ` Ingo Molnar
2012-10-15 0:32 Stephen Rothwell
2012-10-10 2:51 Stephen Rothwell
2012-10-10 2:45 Stephen Rothwell
2012-06-26 4:36 Stephen Rothwell
2012-06-22 5:01 Stephen Rothwell
2012-06-04 3:52 Stephen Rothwell
2012-05-22 5:44 Stephen Rothwell
2012-01-03 5:16 Stephen Rothwell
2012-01-03 5:08 Stephen Rothwell
2012-01-03 8:06 ` Ingo Molnar
2012-01-03 8:36 ` Stephen Rothwell
2011-04-14 3:14 Stephen Rothwell
2011-04-14 9:02 ` Peter Zijlstra
2011-04-14 9:25 ` Ingo Molnar
2011-04-08 5:02 Stephen Rothwell
2011-03-16 5:08 Stephen Rothwell
2011-03-16 8:50 ` Sebastian Andrzej Siewior
2011-03-16 11:02 ` Stephen Rothwell
2010-10-22 2:08 Stephen Rothwell
2010-10-06 2:47 Stephen Rothwell
2010-09-23 3:32 Stephen Rothwell
2010-07-26 3:39 Stephen Rothwell
2010-01-18 7:08 Stephen Rothwell
2010-01-18 7:50 ` Ingo Molnar
2010-01-18 8:59 ` Stephen Rothwell
2009-12-09 4:06 Stephen Rothwell
2009-09-24 4:07 Stephen Rothwell
2009-09-24 8:33 ` Ingo Molnar
2009-09-24 9:23 ` Stephen Rothwell
2009-08-19 6:07 Stephen Rothwell
2009-08-19 10:37 ` Ingo Molnar
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