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From: Will Deacon <will@kernel.org>
To: Peter Zijlstra <peterz@infradead.org>
Cc: linux-arch@vger.kernel.org, Juri Lelli <juri.lelli@redhat.com>,
	kernel-team@android.com,
	Vincent Guittot <vincent.guittot@linaro.org>,
	Quentin Perret <qperret@google.com>,
	Catalin Marinas <catalin.marinas@arm.com>,
	Johannes Weiner <hannes@cmpxchg.org>,
	linux-kernel@vger.kernel.org, Qais Yousef <qais.yousef@arm.com>,
	Ingo Molnar <mingo@redhat.com>, Li Zefan <lizefan@huawei.com>,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	Marc Zyngier <maz@kernel.org>, Tejun Heo <tj@kernel.org>,
	Suren Baghdasaryan <surenb@google.com>,
	Morten Rasmussen <morten.rasmussen@arm.com>,
	linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH v3 08/14] arm64: exec: Adjust affinity for compat tasks with mismatched 32-bit EL0
Date: Thu, 19 Nov 2020 16:30:36 +0000	[thread overview]
Message-ID: <20201119163035.GB4582@willie-the-truck> (raw)
In-Reply-To: <20201119161956.GS3121392@hirez.programming.kicks-ass.net>

On Thu, Nov 19, 2020 at 05:19:56PM +0100, Peter Zijlstra wrote:
> On Thu, Nov 19, 2020 at 11:06:04AM +0000, Will Deacon wrote:
> > On Thu, Nov 19, 2020 at 09:24:07AM +0000, Quentin Perret wrote:
> > > On Friday 13 Nov 2020 at 09:37:13 (+0000), Will Deacon wrote:
> > > > When exec'ing a 32-bit task on a system with mismatched support for
> > > > 32-bit EL0, try to ensure that it starts life on a CPU that can actually
> > > > run it.
> > > > 
> > > > Signed-off-by: Will Deacon <will@kernel.org>
> > > > ---
> > > >  arch/arm64/kernel/process.c | 12 +++++++++++-
> > > >  1 file changed, 11 insertions(+), 1 deletion(-)
> > > > 
> > > > diff --git a/arch/arm64/kernel/process.c b/arch/arm64/kernel/process.c
> > > > index 1540ab0fbf23..17b94007fed4 100644
> > > > --- a/arch/arm64/kernel/process.c
> > > > +++ b/arch/arm64/kernel/process.c
> > > > @@ -625,6 +625,16 @@ unsigned long arch_align_stack(unsigned long sp)
> > > >  	return sp & ~0xf;
> > > >  }
> > > >  
> > > > +static void adjust_compat_task_affinity(struct task_struct *p)
> > > > +{
> > > > +	const struct cpumask *mask = system_32bit_el0_cpumask();
> > > > +
> > > > +	if (restrict_cpus_allowed_ptr(p, mask))
> > > > +		set_cpus_allowed_ptr(p, mask);
> > > 
> > > My understanding of this call to set_cpus_allowed_ptr() is that you're
> > > mimicking the hotplug vs affinity case behaviour in some ways. That is,
> > > if a task is pinned to a CPU and userspace hotplugs that CPU, then the
> > > kernel will reset the affinity of the task to the remaining online CPUs.
> > 
> > Correct. It looks to the 32-bit application like all the 64-bit-only CPUs
> > were hotplugged off at the point of the execve().
> 
> This doesn't respect cpusets though :/

How does that differ from select_fallback_rq()?

Will

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  reply	other threads:[~2020-11-19 16:31 UTC|newest]

Thread overview: 52+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-11-13  9:37 [PATCH v3 00/14] An alternative series for asymmetric AArch32 systems Will Deacon
2020-11-13  9:37 ` [PATCH v3 01/14] arm64: cpuinfo: Split AArch32 registers out into a separate struct Will Deacon
2020-11-13  9:37 ` [PATCH v3 02/14] arm64: Allow mismatched 32-bit EL0 support Will Deacon
2020-11-19 11:27   ` Valentin Schneider
2020-11-19 13:12     ` Will Deacon
2020-11-13  9:37 ` [PATCH v3 03/14] KVM: arm64: Kill 32-bit vCPUs on systems with mismatched " Will Deacon
2020-11-13  9:37 ` [PATCH v3 04/14] arm64: Kill 32-bit applications scheduled on 64-bit-only CPUs Will Deacon
2020-11-13  9:37 ` [PATCH v3 05/14] arm64: Advertise CPUs capable of running 32-bit applications in sysfs Will Deacon
2020-11-13  9:37 ` [PATCH v3 06/14] arm64: Hook up cmdline parameter to allow mismatched 32-bit EL0 Will Deacon
2020-11-13  9:37 ` [PATCH v3 07/14] sched: Introduce restrict_cpus_allowed_ptr() to limit task CPU affinity Will Deacon
2020-11-19  9:18   ` Quentin Perret
2020-11-19 11:03     ` Quentin Perret
2020-11-19 11:05     ` Will Deacon
2020-11-19 11:27       ` Valentin Schneider
2020-11-19 13:13         ` Will Deacon
2020-11-19 14:54           ` Valentin Schneider
2020-11-19 16:41             ` Will Deacon
2020-11-19 12:47   ` Valentin Schneider
2020-11-19 13:13     ` Will Deacon
2020-11-19 14:54       ` Valentin Schneider
2020-11-19 16:09       ` Peter Zijlstra
2020-11-19 16:57         ` Valentin Schneider
2020-11-19 19:25           ` Will Deacon
2020-11-13  9:37 ` [PATCH v3 08/14] arm64: exec: Adjust affinity for compat tasks with mismatched 32-bit EL0 Will Deacon
2020-11-19  9:24   ` Quentin Perret
2020-11-19 11:06     ` Will Deacon
2020-11-19 16:19       ` Peter Zijlstra
2020-11-19 16:30         ` Will Deacon [this message]
2020-11-19 16:44           ` Peter Zijlstra
2020-11-19 16:51             ` Will Deacon
2020-11-19 16:14   ` Peter Zijlstra
2020-11-19 16:28     ` Will Deacon
2020-11-19 16:42       ` Peter Zijlstra
2020-11-19 16:48         ` Will Deacon
2020-11-13  9:37 ` [PATCH v3 09/14] cpuset: Don't use the cpu_possible_mask as a last resort for cgroup v1 Will Deacon
2020-11-19  9:29   ` Quentin Perret
2020-11-19 11:06     ` Will Deacon
2020-11-13  9:37 ` [PATCH v3 10/14] sched: Introduce arch_cpu_allowed_mask() to limit fallback rq selection Will Deacon
2020-11-19  9:38   ` Quentin Perret
2020-11-19 11:07     ` Will Deacon
2020-11-19 20:39       ` Will Deacon
2020-11-23 14:48         ` Quentin Perret
2020-11-13  9:37 ` [PATCH v3 11/14] sched: Reject CPU affinity changes based on arch_cpu_allowed_mask() Will Deacon
2020-11-19  9:47   ` Quentin Perret
2020-11-19 11:07     ` Will Deacon
2020-11-19 14:30       ` Quentin Perret
2020-11-19 16:44         ` Will Deacon
2020-11-13  9:37 ` [PATCH v3 12/14] arm64: Prevent offlining first CPU with 32-bit EL0 on mismatched system Will Deacon
2020-11-13  9:37 ` [PATCH v3 13/14] arm64: Implement arch_cpu_allowed_mask() Will Deacon
2020-11-13  9:37 ` [PATCH v3 14/14] arm64: Remove logic to kill 32-bit tasks on 64-bit-only cores Will Deacon
2020-11-19 16:11 ` [PATCH v3 00/14] An alternative series for asymmetric AArch32 systems Peter Zijlstra
2020-11-19 16:39   ` Will Deacon

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