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.
_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
WARNING: multiple messages have this Message-ID (diff)
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.
next prev parent reply other threads:[~2021-10-27 12:21 UTC|newest]
Thread overview: 8+ 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
2021-10-18 14:47 ` Nicolas Saenz Julienne
2021-10-27 11:26 ` Mark Rutland
2021-10-27 11:26 ` Mark Rutland
2021-10-27 12:20 ` Marc Zyngier [this message]
2021-10-27 12:20 ` Marc Zyngier
2021-10-28 9:20 ` Will Deacon
2021-10-28 9:20 ` Will Deacon
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=875ytibqwo.wl-maz@kernel.org \
--to=maz@kernel.org \
--cc=catalin.marinas@arm.com \
--cc=linux-arm-kernel@lists.infradead.org \
--cc=linux-kernel@vger.kernel.org \
--cc=mark.rutland@arm.com \
--cc=nsaenzju@redhat.com \
--cc=tglx@linutronix.de \
--cc=will@kernel.org \
/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 an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.