Re: [PATCH v6 21/21] Documentation: arm64: describe asymmetric 32-bit support
From: Qais Yousef
Date: Fri May 21 2021 - 13:37:36 EST
On 05/18/21 10:47, Will Deacon wrote:
> Document support for running 32-bit tasks on asymmetric 32-bit systems
> and its impact on the user ABI when enabled.
> Signed-off-by: Will Deacon <will@xxxxxxxxxx>
> .../admin-guide/kernel-parameters.txt | 3 +
> Documentation/arm64/asymmetric-32bit.rst | 149 ++++++++++++++++++
> Documentation/arm64/index.rst | 1 +
> 3 files changed, 153 insertions(+)
> create mode 100644 Documentation/arm64/asymmetric-32bit.rst
> +The affinity of a 32-bit task may include CPUs that are not explicitly
> +allowed by the cpuset to which it is attached. This can occur as a
> +result of the following two situations:
> + - A 64-bit task attached to a cpuset which allows only 64-bit CPUs
> + executes a 32-bit program.
> + - All of the 32-bit-capable CPUs allowed by a cpuset containing a
> + 32-bit task are offlined.
> +In both of these cases, the new affinity is calculated according to step
> +(2) of the process described in `execve(2)`_ and the cpuset hierarchy is
> +unchanged irrespective of the cgroup version.
nit: Should we call out that we're breaking cpuset-v1 behavior? Don't feel
strongly about it.