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From: Peter Zijlstra <peterz@infradead.org>
To: Will Deacon <will@kernel.org>
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>,
	Morten Rasmussen <morten.rasmussen@arm.com>,
	Qais Yousef <qais.yousef@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 v5 00/15] An alternative series for asymmetric AArch32 systems
Date: Thu, 17 Dec 2020 11:55:33 +0100	[thread overview]
Message-ID: <20201217105533.GV3040@hirez.programming.kicks-ass.net> (raw)
In-Reply-To: <20201215185012.GA15566@willie-the-truck>

On Tue, Dec 15, 2020 at 06:50:12PM +0000, Will Deacon wrote:
> On Tue, Dec 15, 2020 at 06:36:45PM +0100, Peter Zijlstra wrote:

> > IOW, any (accidental or otherwise) trip through a 32bit helper, will
> > destroy user state (the affinity mask: 0x3c).
> 
> Yes, that's correct, and I agree that it's a rough edge. If you're happy
> with the idea of adding an extra mask to make this work, then I can start
> hacking that up

Yeah, I'm afraid we'll have to, this asymmetric muck is only going to
get worse from here on.

Anyway, I think we can avoid adding another cpumask_t to task_struct and
do with a cpumask_t * insteads. After all, for 'normal' tasks, the
task_cpu_possible_mask() will be cpu_possible_mask and we don't need to
carry anything extra.

Only once we hit one of these assymetric ISA things, can the task
allocate the additional cpumask and retain the full mask.

> (although I doubt I'll get something out before the new
> year at this point).

Yeah, we're all about to shut down for a bit, I'll not be looking at
email for 2 weeks either, so even if you send it, I might not see it
until the next year.


WARNING: multiple messages have this Message-ID (diff)
From: Peter Zijlstra <peterz@infradead.org>
To: Will Deacon <will@kernel.org>
Cc: linux-arch@vger.kernel.org, Marc Zyngier <maz@kernel.org>,
	kernel-team@android.com,
	Vincent Guittot <vincent.guittot@linaro.org>,
	Juri Lelli <juri.lelli@redhat.com>,
	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>,
	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 v5 00/15] An alternative series for asymmetric AArch32 systems
Date: Thu, 17 Dec 2020 11:55:33 +0100	[thread overview]
Message-ID: <20201217105533.GV3040@hirez.programming.kicks-ass.net> (raw)
In-Reply-To: <20201215185012.GA15566@willie-the-truck>

On Tue, Dec 15, 2020 at 06:50:12PM +0000, Will Deacon wrote:
> On Tue, Dec 15, 2020 at 06:36:45PM +0100, Peter Zijlstra wrote:

> > IOW, any (accidental or otherwise) trip through a 32bit helper, will
> > destroy user state (the affinity mask: 0x3c).
> 
> Yes, that's correct, and I agree that it's a rough edge. If you're happy
> with the idea of adding an extra mask to make this work, then I can start
> hacking that up

Yeah, I'm afraid we'll have to, this asymmetric muck is only going to
get worse from here on.

Anyway, I think we can avoid adding another cpumask_t to task_struct and
do with a cpumask_t * insteads. After all, for 'normal' tasks, the
task_cpu_possible_mask() will be cpu_possible_mask and we don't need to
carry anything extra.

Only once we hit one of these assymetric ISA things, can the task
allocate the additional cpumask and retain the full mask.

> (although I doubt I'll get something out before the new
> year at this point).

Yeah, we're all about to shut down for a bit, I'll not be looking at
email for 2 weeks either, so even if you send it, I might not see it
until the next year.


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  reply	other threads:[~2020-12-17 10:56 UTC|newest]

Thread overview: 58+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-12-08 13:28 [PATCH v5 00/15] An alternative series for asymmetric AArch32 systems Will Deacon
2020-12-08 13:28 ` Will Deacon
2020-12-08 13:28 ` [PATCH v5 01/15] arm64: cpuinfo: Split AArch32 registers out into a separate struct Will Deacon
2020-12-08 13:28   ` Will Deacon
2020-12-08 13:28 ` [PATCH v5 02/15] arm64: Allow mismatched 32-bit EL0 support Will Deacon
2020-12-08 13:28   ` Will Deacon
2020-12-08 13:28 ` [PATCH v5 03/15] KVM: arm64: Kill 32-bit vCPUs on systems with mismatched " Will Deacon
2020-12-08 13:28   ` Will Deacon
2020-12-08 13:28 ` [PATCH v5 04/15] arm64: Kill 32-bit applications scheduled on 64-bit-only CPUs Will Deacon
2020-12-08 13:28   ` Will Deacon
2020-12-08 13:28 ` [PATCH v5 05/15] arm64: Advertise CPUs capable of running 32-bit applications in sysfs Will Deacon
2020-12-08 13:28   ` Will Deacon
2020-12-08 13:28 ` [PATCH v5 06/15] sched: Introduce task_cpu_possible_mask() to limit fallback rq selection Will Deacon
2020-12-08 13:28   ` Will Deacon
2020-12-08 13:28 ` [PATCH v5 07/15] cpuset: Don't use the cpu_possible_mask as a last resort for cgroup v1 Will Deacon
2020-12-08 13:28   ` Will Deacon
2020-12-17 12:15   ` Qais Yousef
2020-12-17 12:15     ` Qais Yousef
2020-12-17 13:44     ` Peter Zijlstra
2020-12-17 13:44       ` Peter Zijlstra
2020-12-17 14:59       ` Will Deacon
2020-12-17 14:59         ` Will Deacon
2020-12-17 15:00       ` Qais Yousef
2020-12-17 15:00         ` Qais Yousef
2020-12-08 13:28 ` [PATCH v5 08/15] cpuset: Honour task_cpu_possible_mask() in guarantee_online_cpus() Will Deacon
2020-12-08 13:28   ` Will Deacon
2020-12-28  3:54   ` Suren Baghdasaryan
2020-12-28  3:54     ` Suren Baghdasaryan
2020-12-08 13:28 ` [PATCH v5 09/15] sched: Reject CPU affinity changes based on task_cpu_possible_mask() Will Deacon
2020-12-08 13:28   ` Will Deacon
2020-12-08 13:28 ` [PATCH v5 10/15] sched: Introduce force_compatible_cpus_allowed_ptr() to limit CPU affinity Will Deacon
2020-12-08 13:28   ` Will Deacon
2020-12-28  4:29   ` Suren Baghdasaryan
2020-12-28  4:29     ` Suren Baghdasaryan
2020-12-08 13:28 ` [PATCH v5 11/15] arm64: Implement task_cpu_possible_mask() Will Deacon
2020-12-08 13:28   ` Will Deacon
2020-12-08 13:28 ` [PATCH v5 12/15] arm64: exec: Adjust affinity for compat tasks with mismatched 32-bit EL0 Will Deacon
2020-12-08 13:28   ` Will Deacon
2020-12-08 13:28 ` [PATCH v5 13/15] arm64: Prevent offlining first CPU with 32-bit EL0 on mismatched system Will Deacon
2020-12-08 13:28   ` Will Deacon
2020-12-08 13:28 ` [PATCH v5 14/15] arm64: Hook up cmdline parameter to allow mismatched 32-bit EL0 Will Deacon
2020-12-08 13:28   ` Will Deacon
2020-12-08 13:28 ` [PATCH v5 15/15] arm64: Remove logic to kill 32-bit tasks on 64-bit-only cores Will Deacon
2020-12-08 13:28   ` Will Deacon
2020-12-15 17:36 ` [PATCH v5 00/15] An alternative series for asymmetric AArch32 systems Peter Zijlstra
2020-12-15 17:36   ` Peter Zijlstra
2020-12-15 18:50   ` Will Deacon
2020-12-15 18:50     ` Will Deacon
2020-12-17 10:55     ` Peter Zijlstra [this message]
2020-12-17 10:55       ` Peter Zijlstra
2020-12-16 11:16 ` Qais Yousef
2020-12-16 11:16   ` Qais Yousef
2020-12-16 14:14   ` Will Deacon
2020-12-16 14:14     ` Will Deacon
2020-12-16 16:48     ` Qais Yousef
2020-12-16 16:48       ` Qais Yousef
2020-12-16 18:21       ` Suren Baghdasaryan
2020-12-16 18:21         ` Suren Baghdasaryan

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