From: Catalin Marinas <catalin.marinas@arm.com>
To: Peter Zijlstra <peterz@infradead.org>
Cc: linux-arch@vger.kernel.org, Marc Zyngier <maz@kernel.org>,
Qais Yousef <qais.yousef@arm.com>,
Linus Torvalds <torvalds@linux-foundation.org>,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
Will Deacon <will@kernel.org>,
Morten Rasmussen <morten.rasmussen@arm.com>,
linux-arm-kernel@lists.infradead.org
Subject: Re: [RFC PATCH 3/3] arm64: Handle AArch32 tasks running on non AArch32 cpu
Date: Fri, 9 Oct 2020 10:51:12 +0100 [thread overview]
Message-ID: <20201009095112.GE23638@gaia> (raw)
In-Reply-To: <20201009092559.GE2628@hirez.programming.kicks-ass.net>
On Fri, Oct 09, 2020 at 11:25:59AM +0200, Peter Zijlstra wrote:
> On Fri, Oct 09, 2020 at 10:13:12AM +0200, Morten Rasmussen wrote:
> > On Fri, Oct 09, 2020 at 09:29:43AM +0200, Peter Zijlstra wrote:
>
> > > Fundamentally, you're not supposed to change the userspace provided
> > > affinity mask. If we want to do something like this, we'll have to teach
> > > the scheduler about this second mask such that it can compute an
> > > effective mask as the intersection between the 'feature' and user mask.
> >
> > I agree that we shouldn't mess wit the user-space mask directly. Would it
> > be unthinkable to go down the route of maintaining a new mask which is
> > the intersection of the feature mask (controlled and updated by arch
> > code) and the user-space mask?
> >
> > It shouldn't add overhead in the scheduler as it would use the
> > intersection mask instead of the user-space mask, the main complexity
> > would be around making sure the intersection mask is updated correctly
> > (cpusets, hotplug, ...).
>
> IFF we _need_ to go there, then yes that was the plan, compose the
> intersection when either the (arch) feature(set) mask or the userspace
> mask changes.
Another thought: should the arm64 compat_elf_check_arch() and
sys_arm64_personality(PER_LINUX32) validate the user cpumask before
returning success/failure? It won't prevent the user from changing the
affinity at run-time but at least it won't randomly get killed just
because the kernel advertises 32-bit support.
--
Catalin
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prev parent reply other threads:[~2020-10-09 9:52 UTC|newest]
Thread overview: 33+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-10-08 18:16 [RFC PATCH 0/3] Add support for Asymmetric AArch32 systems Qais Yousef
2020-10-08 18:16 ` [RFC PATCH 1/3] arm64: kvm: Handle " Qais Yousef
2020-10-09 8:12 ` Marc Zyngier
2020-10-09 9:58 ` Qais Yousef
2020-10-09 12:34 ` Marc Zyngier
2020-10-09 12:48 ` Qais Yousef
2020-10-12 15:32 ` James Morse
2020-10-13 10:32 ` Marc Zyngier
2020-10-13 11:51 ` James Morse
2020-10-13 11:59 ` Qais Yousef
2020-10-13 12:09 ` Marc Zyngier
2020-10-13 12:16 ` Qais Yousef
2020-10-08 18:16 ` [RFC PATCH 2/3] arm64: Add support for asymmetric AArch32 EL0 configurations Qais Yousef
2020-10-08 18:22 ` Randy Dunlap
2020-10-12 10:22 ` Qais Yousef
2020-10-09 6:13 ` Greg Kroah-Hartman
2020-10-09 8:40 ` Will Deacon
2020-10-09 8:50 ` Catalin Marinas
2020-10-09 9:39 ` Catalin Marinas
2020-10-12 12:46 ` Qais Yousef
2020-10-08 18:16 ` [RFC PATCH 3/3] arm64: Handle AArch32 tasks running on non AArch32 cpu Qais Yousef
2020-10-09 7:29 ` Peter Zijlstra
2020-10-09 8:13 ` Morten Rasmussen
2020-10-09 8:31 ` Will Deacon
2020-10-09 8:50 ` Morten Rasmussen
2020-10-09 9:33 ` Catalin Marinas
2020-10-09 9:42 ` Greg Kroah-Hartman
2020-10-09 11:31 ` Qais Yousef
2020-10-09 12:40 ` Catalin Marinas
2020-10-13 14:23 ` Qais Yousef
2020-10-09 9:25 ` Peter Zijlstra
2020-10-09 9:39 ` Qais Yousef
2020-10-09 9:51 ` Catalin Marinas [this message]
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