From: Peter Zijlstra <peterz@infradead.org>
To: Mark Rutland <mark.rutland@arm.com>
Cc: Ard Biesheuvel <ardb@kernel.org>,
Frederic Weisbecker <frederic@kernel.org>,
LKML <linux-kernel@vger.kernel.org>,
James Morse <james.morse@arm.com>,
David Laight <David.Laight@aculab.com>,
Quentin Perret <qperret@google.com>,
Catalin Marinas <catalin.marinas@arm.com>,
Will Deacon <will@kernel.org>
Subject: Re: [PATCH 2/4] arm64: implement support for static call trampolines
Date: Tue, 26 Oct 2021 12:45:55 +0200 [thread overview]
Message-ID: <YXfcY7PPAvOK9E+8@hirez.programming.kicks-ass.net> (raw)
In-Reply-To: <20211026103655.GB30152@C02TD0UTHF1T.local>
On Tue, Oct 26, 2021 at 11:36:55AM +0100, Mark Rutland wrote:
> My preference overall is to keep the trampoline self-contained, and I'd
> prefer to keep the RET inline in the trampoline rather than trying to
> factor it out so that all the control-flow is clearly in one place.
>
> So I'd prefer that we have the sequence as-is:
>
> | 0: .quad 0x0
> | bti c
> | < insn >
> | ldr x16, 0b
> | cbz x16, 1f
> | br x16
> | 1: ret
OK, fair enough. In that case:
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Although I do think that function can use a comment to explain the magic
involved.
> If we knew these were only called with IRQs enabled (and so we can take
> an IPI to generate a context synchronization event), we could patch
> <insn> to a RET and point the literal back at the BTI, e.g.
Given the static_call() usage on x86 I'm pretty sure you'll want them
with IRQs disabled.
next prev parent reply other threads:[~2021-10-26 10:46 UTC|newest]
Thread overview: 30+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-10-25 12:20 [PATCH 0/4] arm64: Support dynamic preemption v2 Frederic Weisbecker
2021-10-25 12:20 ` [PATCH 1/4] sched/preempt: Prepare for supporting !CONFIG_GENERIC_ENTRY dynamic preemption Frederic Weisbecker
2021-10-25 12:21 ` [PATCH 2/4] arm64: implement support for static call trampolines Frederic Weisbecker
2021-10-25 13:56 ` Peter Zijlstra
2021-10-25 14:08 ` Ard Biesheuvel
2021-10-25 14:19 ` Peter Zijlstra
2021-10-25 14:44 ` Peter Zijlstra
2021-10-25 14:55 ` Ard Biesheuvel
2021-10-25 15:03 ` Peter Zijlstra
2021-10-25 15:10 ` Ard Biesheuvel
2021-10-26 10:36 ` Mark Rutland
2021-10-26 10:45 ` Peter Zijlstra [this message]
2021-10-26 11:06 ` David Laight
2021-10-27 12:47 ` Mark Rutland
2021-10-25 15:03 ` David Laight
2021-10-25 14:25 ` David Laight
2021-10-25 14:31 ` Ard Biesheuvel
2021-10-25 14:38 ` David Laight
2021-10-25 12:21 ` [PATCH 3/4] arm64: Implement IRQ exit preemption static call for dynamic preemption Frederic Weisbecker
2021-10-25 12:21 ` [PATCH 4/4] arm64: Implement HAVE_PREEMPT_DYNAMIC Frederic Weisbecker
-- strict thread matches above, loose matches on Subject: below --
2021-09-20 23:32 [PATCH 0/4] arm64: Support dynamic preemption Frederic Weisbecker
2021-09-20 23:32 ` [PATCH 2/4] arm64: implement support for static call trampolines Frederic Weisbecker
2021-09-21 7:09 ` Peter Zijlstra
2021-09-21 14:44 ` Ard Biesheuvel
2021-09-21 15:08 ` Peter Zijlstra
2021-09-21 15:33 ` Mark Rutland
2021-09-21 15:55 ` Ard Biesheuvel
2021-09-21 16:28 ` Mark Rutland
2021-09-25 17:46 ` David Laight
2021-09-27 8:58 ` Mark Rutland
2021-09-21 16:10 ` Ard Biesheuvel
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