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From: Will Deacon <will@kernel.org>
To: Qais Yousef <qais.yousef@arm.com>
Cc: linux-arm-kernel@lists.infradead.org, linux-arch@vger.kernel.org,
	linux-kernel@vger.kernel.org,
	Catalin Marinas <catalin.marinas@arm.com>,
	Marc Zyngier <maz@kernel.org>,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	Peter Zijlstra <peterz@infradead.org>,
	Morten Rasmussen <morten.rasmussen@arm.com>,
	Suren Baghdasaryan <surenb@google.com>,
	Quentin Perret <qperret@google.com>, Tejun Heo <tj@kernel.org>,
	Li Zefan <lizefan@huawei.com>,
	Johannes Weiner <hannes@cmpxchg.org>,
	Ingo Molnar <mingo@redhat.com>,
	Juri Lelli <juri.lelli@redhat.com>,
	Vincent Guittot <vincent.guittot@linaro.org>,
	kernel-team@android.com
Subject: Re: [PATCH v4 04/14] arm64: Kill 32-bit applications scheduled on 64-bit-only CPUs
Date: Wed, 2 Dec 2020 17:42:48 +0000	[thread overview]
Message-ID: <20201202174247.GB29939@willie-the-truck> (raw)
In-Reply-To: <20201202135216.7jilpcvocnqqp5aj@e107158-lin.cambridge.arm.com>

On Wed, Dec 02, 2020 at 01:52:16PM +0000, Qais Yousef wrote:
> On 12/01/20 16:56, Will Deacon wrote:
> > On Fri, Nov 27, 2020 at 01:12:17PM +0000, Qais Yousef wrote:
> > > On 11/24/20 15:50, Will Deacon wrote:
> > > > Scheduling a 32-bit application on a 64-bit-only CPU is a bad idea.
> > > > 
> > > > Ensure that 32-bit applications always take the slow-path when returning
> > > > to userspace on a system with mismatched support at EL0, so that we can
> > > > avoid trying to run on a 64-bit-only CPU and force a SIGKILL instead.
> > > > 
> > > > Signed-off-by: Will Deacon <will@kernel.org>
> > > > ---
> > > 
> > > nit: We drop this patch at the end. Can't we avoid it altogether instead?
> > 
> > I did it like this so that the last patch can be reverted for
> > testing/debugging, but also because I think it helps the structure of the
> > series.
> 
> Cool. I had a comment about the barrier(), you were worried about
> cpu_affinity_invalid() being inlined by the compiler and then things get
> mangled such that TIF_NOTIFY_RESUME clearing is moved after the call as you
> described? Can the compiler move things if cpu_affinity_invalid() is a proper
> function call (not inlined)?

I think function calls implicitly clobber memory, but you'd have to annotate
the thing as noinline to prevent it being inlined.

Will

  reply	other threads:[~2020-12-02 17:43 UTC|newest]

Thread overview: 61+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-11-24 15:50 [PATCH v4 00/14] An alternative series for asymmetric AArch32 systems Will Deacon
2020-11-24 15:50 ` [PATCH v4 01/14] arm64: cpuinfo: Split AArch32 registers out into a separate struct Will Deacon
2020-11-24 15:50 ` [PATCH v4 02/14] arm64: Allow mismatched 32-bit EL0 support Will Deacon
2020-11-27 10:25   ` Marc Zyngier
2020-11-27 11:50     ` Will Deacon
2020-11-27 13:09   ` Qais Yousef
2020-12-01 16:56     ` Will Deacon
2020-12-02 13:16       ` Qais Yousef
2020-11-24 15:50 ` [PATCH v4 03/14] KVM: arm64: Kill 32-bit vCPUs on systems with mismatched " Will Deacon
2020-11-27 10:26   ` Marc Zyngier
2020-11-27 11:53     ` Will Deacon
2020-11-27 17:14       ` Marc Zyngier
2020-11-27 17:24         ` Quentin Perret
2020-11-27 18:16           ` Marc Zyngier
2020-12-01 16:57             ` Will Deacon
2020-12-02  8:18               ` Marc Zyngier
2020-12-02 17:27                 ` Will Deacon
2020-11-24 15:50 ` [PATCH v4 04/14] arm64: Kill 32-bit applications scheduled on 64-bit-only CPUs Will Deacon
2020-11-27 13:12   ` Qais Yousef
2020-12-01 16:56     ` Will Deacon
2020-12-02 13:52       ` Qais Yousef
2020-12-02 17:42         ` Will Deacon [this message]
2020-11-24 15:50 ` [PATCH v4 05/14] arm64: Advertise CPUs capable of running 32-bit applications in sysfs Will Deacon
2020-11-24 15:50 ` [PATCH v4 06/14] arm64: Hook up cmdline parameter to allow mismatched 32-bit EL0 Will Deacon
2020-11-27 13:17   ` Qais Yousef
2020-12-01 16:56     ` Will Deacon
2020-11-24 15:50 ` [PATCH v4 07/14] sched: Introduce restrict_cpus_allowed_ptr() to limit task CPU affinity Will Deacon
2020-11-27  9:49   ` Quentin Perret
2020-11-27 13:19   ` Qais Yousef
2020-12-01 16:56     ` Will Deacon
2020-12-02 13:06       ` Qais Yousef
2020-11-24 15:50 ` [PATCH v4 08/14] arm64: exec: Adjust affinity for compat tasks with mismatched 32-bit EL0 Will Deacon
2020-11-27 10:01   ` Quentin Perret
2020-11-27 13:23   ` Qais Yousef
2020-12-01 16:55     ` Will Deacon
2020-12-02 14:07       ` Qais Yousef
2020-11-24 15:50 ` [PATCH v4 09/14] cpuset: Don't use the cpu_possible_mask as a last resort for cgroup v1 Will Deacon
2020-11-27 13:32   ` Qais Yousef
2020-11-30 17:05     ` Qais Yousef
2020-11-30 17:36       ` Quentin Perret
2020-12-01 11:58         ` Qais Yousef
2020-12-01 12:37           ` Quentin Perret
2020-12-01 14:11             ` Qais Yousef
2020-12-01 15:56               ` Quentin Perret
2020-12-01 22:30                 ` Will Deacon
2020-12-02 11:34                   ` Qais Yousef
2020-12-02 11:33                 ` Qais Yousef
2020-11-24 15:50 ` [PATCH v4 10/14] sched: Introduce arch_task_cpu_possible_mask() to limit fallback rq selection Will Deacon
2020-11-24 15:50 ` [PATCH v4 11/14] sched: Reject CPU affinity changes based on arch_task_cpu_possible_mask() Will Deacon
2020-11-27  9:54   ` Quentin Perret
2020-11-24 15:50 ` [PATCH v4 12/14] arm64: Prevent offlining first CPU with 32-bit EL0 on mismatched system Will Deacon
2020-11-27 13:41   ` Qais Yousef
2020-12-01 22:13     ` Will Deacon
2020-12-02 12:59       ` Qais Yousef
2020-12-02 17:42         ` Will Deacon
2020-12-02 18:08           ` Qais Yousef
2020-11-24 15:50 ` [PATCH v4 13/14] arm64: Implement arch_task_cpu_possible_mask() Will Deacon
2020-11-27 13:41   ` Qais Yousef
2020-11-24 15:50 ` [PATCH v4 14/14] arm64: Remove logic to kill 32-bit tasks on 64-bit-only cores Will Deacon
2020-11-27 13:58 ` [PATCH v4 00/14] An alternative series for asymmetric AArch32 systems Qais Yousef
2020-12-05 20:43 ` Pavel Machek

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