From: Marc Zyngier <maz@kernel.org>
To: Mark Rutland <mark.rutland@arm.com>
Cc: Nicolas Saenz Julienne <nsaenzju@redhat.com>,
catalin.marinas@arm.com, will@kernel.org, tglx@linutronix.de,
linux-arm-kernel@lists.infradead.org,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH] arm64: Select POSIX_CPU_TIMERS_TASK_WORK
Date: Wed, 27 Oct 2021 13:20:23 +0100 [thread overview]
Message-ID: <875ytibqwo.wl-maz@kernel.org> (raw)
In-Reply-To: <20211027112658.GA54628@C02TD0UTHF1T.local>
On Wed, 27 Oct 2021 12:26:58 +0100,
Mark Rutland <mark.rutland@arm.com> wrote:
>
> [adding Marc Z to Cc, since this affects KVM]
>
> On Mon, Oct 18, 2021 at 04:47:13PM +0200, Nicolas Saenz Julienne wrote:
> > With 6caa5812e2d1 ("KVM: arm64: Use generic KVM xfer to guest work
> > function") all arm64 exit paths are properly equipped to handle the
> > POSIX timers' task work.
> >
> > Deferring timer callbacks to thread context, not only limits the amount
> > of time spent in hard interrupt context, but is a safer
> > implementation[1], and will allow PREEMPT_RT setups to use KVM[2].
> >
> > So let's enable POSIX_CPU_TIMERS_TASK_WORK on arm64.
> >
> > [1] https://lore.kernel.org/all/20200716201923.228696399@linutronix.de/
> > [2] https://www.spinics.net/lists/linux-rt-users/msg24860.html
>
> Trivial nit: could we please make that second link:
>
> https://lore.kernel.org/linux-rt-users/87v92bdnlx.ffs@tglx/
>
> > Signed-off-by: Nicolas Saenz Julienne <nsaenzju@redhat.com>
>
> Regardless, this makes sense to me, and given you've tested it:
>
> Acked-by: Mark Rutland <mark.rutland@arm.com>
>
> Thanks,
> Mark.
>
> >
> > ---
> >
> > This was tested by running all relevant kernel timer self-tests and
> > making sure KVM still works as expected.
> >
> > arch/arm64/Kconfig | 1 +
> > 1 file changed, 1 insertion(+)
> >
> > diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
> > index 789036cf74f5..ce0d0d254542 100644
> > --- a/arch/arm64/Kconfig
> > +++ b/arch/arm64/Kconfig
> > @@ -191,6 +191,7 @@ config ARM64
> > select HAVE_PERF_REGS
> > select HAVE_PERF_USER_STACK_DUMP
> > select HAVE_REGS_AND_STACK_ACCESS_API
> > + select HAVE_POSIX_CPU_TIMERS_TASK_WORK
> > select HAVE_FUNCTION_ARG_ACCESS_API
> > select HAVE_FUTEX_CMPXCHG if FUTEX
> > select MMU_GATHER_RCU_TABLE_FREE
Looks reasonable to me.
Acked-by: Marc Zyngier <maz@kernel.org>
M.
--
Without deviation from the norm, progress is not possible.
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next prev parent reply other threads:[~2021-10-27 12:21 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-10-18 14:47 [PATCH] arm64: Select POSIX_CPU_TIMERS_TASK_WORK Nicolas Saenz Julienne
2021-10-27 11:26 ` Mark Rutland
2021-10-27 12:20 ` Marc Zyngier [this message]
2021-10-28 9:20 ` Will Deacon
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