From: Catalin Marinas <catalin.marinas@arm.com>
To: Morten Rasmussen <morten.rasmussen@arm.com>
Cc: Marc Zyngier <maz@kernel.org>,
linux-arch@vger.kernel.org, Will Deacon <will@kernel.org>,
"Peter Zijlstra (Intel)" <peterz@infradead.org>,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
James Morse <james.morse@arm.com>,
Linus Torvalds <torvalds@linux-foundation.org>,
Qais Yousef <qais.yousef@arm.com>,
linux-arm-kernel@lists.infradead.org
Subject: Re: [RFC PATCH v2 4/4] arm64: Export id_aar64fpr0 via sysfs
Date: Wed, 21 Oct 2020 15:09:46 +0100 [thread overview]
Message-ID: <20201021140945.GD3976@gaia> (raw)
In-Reply-To: <20201021133316.GF8004@e123083-lin>
On Wed, Oct 21, 2020 at 03:33:29PM +0200, Morten Rasmussen wrote:
> On Wed, Oct 21, 2020 at 01:15:59PM +0100, Catalin Marinas wrote:
> > one, though not as easy as automatic task placement by the scheduler (my
> > first preference, followed by the id_* regs and the aarch32 mask, though
> > not a strong preference for any).
>
> Automatic task placement by the scheduler would mean giving up the
> requirement that the user-space affinity mask must always be honoured.
> Is that on the table?
I think Peter rejected it but I still find it a nicer interface from a
dumb application perspective. It may interact badly with cpusets though
(at least on Android).
> Killing aarch32 tasks with an empty intersection between the
> user-space mask and aarch32_mask is not really "automatic" and would
> require the aarch32 capability to be exposed anyway.
I agree, especially if overriding the user mask is not desirable. But if
one doesn't play around with cpusets, 32-bit apps would run "fine" with
the scheduler transparently placing them on the correct CPU.
Anyway, if the task placement is entirely off the table, the next thing
is asking applications to set their own mask and kill them if they do
the wrong thing. Here I see two possibilities for killing an app:
1. When it ends up scheduled on a non-AArch32-capable CPU
2. If the user cpumask (bar the offline CPUs) is not a subset of the
aarch32_mask
Option 1 is simpler but 2 would be slightly more consistent.
There's also the question on whether the kernel should allow an ELF32 to
be loaded (and potentially killed subsequently) if the user mask is not
correct on execve().
--
Catalin
WARNING: multiple messages have this Message-ID (diff)
From: Catalin Marinas <catalin.marinas@arm.com>
To: Morten Rasmussen <morten.rasmussen@arm.com>
Cc: linux-arch@vger.kernel.org,
"Peter Zijlstra \(Intel\)" <peterz@infradead.org>,
Marc Zyngier <maz@kernel.org>,
Linus Torvalds <torvalds@linux-foundation.org>,
James Morse <james.morse@arm.com>,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
Will Deacon <will@kernel.org>, Qais Yousef <qais.yousef@arm.com>,
linux-arm-kernel@lists.infradead.org
Subject: Re: [RFC PATCH v2 4/4] arm64: Export id_aar64fpr0 via sysfs
Date: Wed, 21 Oct 2020 15:09:46 +0100 [thread overview]
Message-ID: <20201021140945.GD3976@gaia> (raw)
In-Reply-To: <20201021133316.GF8004@e123083-lin>
On Wed, Oct 21, 2020 at 03:33:29PM +0200, Morten Rasmussen wrote:
> On Wed, Oct 21, 2020 at 01:15:59PM +0100, Catalin Marinas wrote:
> > one, though not as easy as automatic task placement by the scheduler (my
> > first preference, followed by the id_* regs and the aarch32 mask, though
> > not a strong preference for any).
>
> Automatic task placement by the scheduler would mean giving up the
> requirement that the user-space affinity mask must always be honoured.
> Is that on the table?
I think Peter rejected it but I still find it a nicer interface from a
dumb application perspective. It may interact badly with cpusets though
(at least on Android).
> Killing aarch32 tasks with an empty intersection between the
> user-space mask and aarch32_mask is not really "automatic" and would
> require the aarch32 capability to be exposed anyway.
I agree, especially if overriding the user mask is not desirable. But if
one doesn't play around with cpusets, 32-bit apps would run "fine" with
the scheduler transparently placing them on the correct CPU.
Anyway, if the task placement is entirely off the table, the next thing
is asking applications to set their own mask and kill them if they do
the wrong thing. Here I see two possibilities for killing an app:
1. When it ends up scheduled on a non-AArch32-capable CPU
2. If the user cpumask (bar the offline CPUs) is not a subset of the
aarch32_mask
Option 1 is simpler but 2 would be slightly more consistent.
There's also the question on whether the kernel should allow an ELF32 to
be loaded (and potentially killed subsequently) if the user mask is not
correct on execve().
--
Catalin
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next prev parent reply other threads:[~2020-10-21 14:09 UTC|newest]
Thread overview: 114+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-10-21 10:46 [RFC PATCH v2 0/4] Add support for Asymmetric AArch32 systems Qais Yousef
2020-10-21 10:46 ` Qais Yousef
2020-10-21 10:46 ` [RFC PATCH v2 1/4] arm64: kvm: Handle " Qais Yousef
2020-10-21 10:46 ` Qais Yousef
2020-10-21 12:02 ` Marc Zyngier
2020-10-21 12:02 ` Marc Zyngier
2020-10-21 13:35 ` Qais Yousef
2020-10-21 13:35 ` Qais Yousef
2020-10-21 13:51 ` Marc Zyngier
2020-10-21 13:51 ` Marc Zyngier
2020-10-21 14:38 ` Qais Yousef
2020-10-21 14:38 ` Qais Yousef
2020-11-02 17:58 ` Qais Yousef
2020-11-02 17:58 ` Qais Yousef
2020-10-21 10:46 ` [RFC PATCH v2 2/4] arm64: Add support for asymmetric AArch32 EL0 configurations Qais Yousef
2020-10-21 10:46 ` Qais Yousef
2020-10-21 15:39 ` Will Deacon
2020-10-21 15:39 ` Will Deacon
2020-10-21 16:21 ` Qais Yousef
2020-10-21 16:21 ` Qais Yousef
2020-10-21 16:52 ` Catalin Marinas
2020-10-21 16:52 ` Catalin Marinas
2020-10-21 17:39 ` Will Deacon
2020-10-21 17:39 ` Will Deacon
2020-10-22 9:53 ` Catalin Marinas
2020-10-22 9:53 ` Catalin Marinas
2020-10-21 10:46 ` [RFC PATCH v2 3/4] arm64: export emulate_sys_reg() Qais Yousef
2020-10-21 10:46 ` Qais Yousef
2020-10-21 10:46 ` [RFC PATCH v2 4/4] arm64: Export id_aar64fpr0 via sysfs Qais Yousef
2020-10-21 10:46 ` Qais Yousef
2020-10-21 11:09 ` Marc Zyngier
2020-10-21 11:09 ` Marc Zyngier
2020-10-21 11:25 ` Greg Kroah-Hartman
2020-10-21 11:25 ` Greg Kroah-Hartman
2020-10-21 11:46 ` Marc Zyngier
2020-10-21 11:46 ` Marc Zyngier
2020-10-21 12:11 ` Greg Kroah-Hartman
2020-10-21 12:11 ` Greg Kroah-Hartman
2020-10-21 13:18 ` Qais Yousef
2020-10-21 13:18 ` Qais Yousef
2020-10-21 12:15 ` Catalin Marinas
2020-10-21 12:15 ` Catalin Marinas
2020-10-21 13:20 ` Qais Yousef
2020-10-21 13:20 ` Qais Yousef
2020-10-21 13:33 ` Morten Rasmussen
2020-10-21 13:33 ` Morten Rasmussen
2020-10-21 14:09 ` Catalin Marinas [this message]
2020-10-21 14:09 ` Catalin Marinas
2020-10-21 14:41 ` Morten Rasmussen
2020-10-21 14:41 ` Morten Rasmussen
2020-10-21 14:45 ` Will Deacon
2020-10-21 14:45 ` Will Deacon
2020-10-21 15:10 ` Catalin Marinas
2020-10-21 15:10 ` Catalin Marinas
2020-10-21 15:37 ` Will Deacon
2020-10-21 15:37 ` Will Deacon
2020-10-21 16:18 ` Catalin Marinas
2020-10-21 16:18 ` Catalin Marinas
2020-10-21 17:19 ` Will Deacon
2020-10-21 17:19 ` Will Deacon
2020-10-22 9:55 ` Morten Rasmussen
2020-10-22 9:55 ` Morten Rasmussen
2020-10-21 14:31 ` Qais Yousef
2020-10-21 14:31 ` Qais Yousef
2020-10-22 10:16 ` Morten Rasmussen
2020-10-22 10:16 ` Morten Rasmussen
2020-10-22 10:48 ` Qais Yousef
2020-10-22 10:48 ` Qais Yousef
2020-10-21 14:41 ` Will Deacon
2020-10-21 14:41 ` Will Deacon
2020-10-21 15:03 ` Qais Yousef
2020-10-21 15:03 ` Qais Yousef
2020-10-21 15:23 ` Will Deacon
2020-10-21 15:23 ` Will Deacon
2020-10-21 16:07 ` Qais Yousef
2020-10-21 16:07 ` Qais Yousef
2020-10-21 17:23 ` Will Deacon
2020-10-21 17:23 ` Will Deacon
2020-10-21 19:57 ` Qais Yousef
2020-10-21 19:57 ` Qais Yousef
2020-10-21 20:26 ` Will Deacon
2020-10-21 20:26 ` Will Deacon
2020-10-22 8:16 ` Catalin Marinas
2020-10-22 8:16 ` Catalin Marinas
2020-10-22 9:58 ` Qais Yousef
2020-10-22 9:58 ` Qais Yousef
2020-10-22 13:47 ` Qais Yousef
2020-10-22 13:47 ` Qais Yousef
2020-10-22 13:55 ` Greg Kroah-Hartman
2020-10-22 13:55 ` Greg Kroah-Hartman
2020-10-22 14:31 ` Catalin Marinas
2020-10-22 14:31 ` Catalin Marinas
2020-10-22 14:34 ` Qais Yousef
2020-10-22 14:34 ` Qais Yousef
2020-10-26 19:02 ` Qais Yousef
2020-10-26 19:02 ` Qais Yousef
2020-10-26 19:08 ` Greg Kroah-Hartman
2020-10-26 19:08 ` Greg Kroah-Hartman
2020-10-26 19:18 ` Qais Yousef
2020-10-26 19:18 ` Qais Yousef
2020-10-21 11:28 ` Greg Kroah-Hartman
2020-10-21 11:28 ` Greg Kroah-Hartman
2020-10-21 13:22 ` Qais Yousef
2020-10-21 13:22 ` Qais Yousef
2020-10-21 11:26 ` [RFC PATCH v2 0/4] Add support for Asymmetric AArch32 systems Greg Kroah-Hartman
2020-10-21 11:26 ` Greg Kroah-Hartman
2020-10-21 13:15 ` Qais Yousef
2020-10-21 13:15 ` Qais Yousef
2020-10-21 13:31 ` Greg Kroah-Hartman
2020-10-21 13:31 ` Greg Kroah-Hartman
2020-10-21 13:55 ` Qais Yousef
2020-10-21 13:55 ` Qais Yousef
2020-10-21 14:35 ` Catalin Marinas
2020-10-21 14:35 ` Catalin Marinas
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