From: Marc Zyngier <maz@kernel.org>
To: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Catalin Marinas <catalin.marinas@arm.com>,
Will Deacon <will@kernel.org>,
linux-arm-kernel@lists.infradead.org, linux-arch@vger.kernel.org,
Peter Zijlstra <peterz@infradead.org>,
Morten Rasmussen <morten.rasmussen@arm.com>,
Qais Yousef <qais.yousef@arm.com>,
Suren Baghdasaryan <surenb@google.com>,
Quentin Perret <qperret@google.com>,
kernel-team@android.com
Subject: Re: [PATCH v2 5/6] arm64: Advertise CPUs capable of running 32-bit applications in sysfs
Date: Tue, 10 Nov 2020 09:53:53 +0000 [thread overview]
Message-ID: <e09e755dd5058103241c1c919d6af076@kernel.org> (raw)
In-Reply-To: <X6pfISu1PE5lelNL@kroah.com>
On 2020-11-10 09:36, Greg Kroah-Hartman wrote:
[...]
> While punting the logic out to userspace is simple for the kernel, and
> of course my first option, I think this isn't going to work in the
> long-run and the kernel will have to "know" what type of process it is
> scheduling in order to correctly deal with this nightmare as userspace
> can't do that well, if at all.
For that to happen, we must first decide which part of the userspace
ABI we are prepared to compromise on. The most obvious one would be to
allow overriding the affinity on exec, but I'm pretty sure it has bad
interactions with cgroups, on top of violating the existing ABI which
mandates that the affinity is inherited across exec.
There may be other options (always make at least one 32bit-capable CPU
part of the process affinity?), but they all imply some form of
userspace
visible regressions.
Pick your poison... :-/
M.
--
Jazz is not dead. It just smells funny...
next prev parent reply other threads:[~2020-11-10 9:53 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-11-09 21:30 [PATCH v2 0/6] An alternative series for asymmetric AArch32 systems Will Deacon
2020-11-09 21:30 ` [PATCH v2 1/6] arm64: cpuinfo: Split AArch32 registers out into a separate struct Will Deacon
2020-11-09 21:30 ` [PATCH v2 2/6] arm64: Allow mismatched 32-bit EL0 support Will Deacon
2020-11-11 19:10 ` Catalin Marinas
2020-11-13 9:36 ` Will Deacon
2020-11-13 10:26 ` Catalin Marinas
2020-11-09 21:30 ` [PATCH v2 3/6] KVM: arm64: Kill 32-bit vCPUs on systems with mismatched " Will Deacon
2020-11-10 9:33 ` Marc Zyngier
2020-11-09 21:30 ` [PATCH v2 4/6] arm64: Kill 32-bit applications scheduled on 64-bit-only CPUs Will Deacon
2020-11-09 21:30 ` [PATCH v2 5/6] arm64: Advertise CPUs capable of running 32-bit applications in sysfs Will Deacon
2020-11-10 7:04 ` Greg Kroah-Hartman
2020-11-10 9:28 ` Catalin Marinas
2020-11-10 9:36 ` Greg Kroah-Hartman
2020-11-10 9:53 ` Marc Zyngier [this message]
2020-11-10 10:10 ` Greg Kroah-Hartman
2020-11-10 10:46 ` Marc Zyngier
2020-11-10 10:57 ` Catalin Marinas
2020-11-09 21:30 ` [PATCH v2 6/6] arm64: Hook up cmdline parameter to allow mismatched 32-bit EL0 Will Deacon
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