- fix arch_memremap_can_ram_remap() which incorrectly passed a PFN to
memblock_is_map_memory rather than the actual address.
- "Disallow kernel mode NEON when IRQs are disabled" - this needs a
better explanation.
"To avoid having to preserve/restore kernel mode NEON state when
such a softirq is taken softirqs are now disabled when using the
NEON from task context." should explain that it's nested kernel
mode. In other words, softirqs from user mode are fine, because
the context will be preserved. softirqs from kernel mode may
be from a context that has already saved the user NEON state, and
thus we would need to preserve the NEON state for the parent kernel
mode context, and this we don't allow.
The problem occurs when the kernel context disables hard IRQs, and
then uses NEON. When it's finished, and restores the userspace NEON
state, we call local_bh_enable() with hard IRQs disabled, which
causes a warning.
This commit addresses that by disallowing the use of NEON with hard
IRQs disabled.
https://lore.kernel.org/all/20250516231858.27899-4-ebiggers@kernel.org/T/#m104841b6e9346b1814c8b0fb9f2340551b0cd3e8
has some further context.
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Merge tag 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/rmk/linux
Pull ARM fixes from Russell King:
- Fix arch_memremap_can_ram_remap() which incorrectly passed a PFN to
memblock_is_map_memory rather than the actual address.
- Disallow kernel mode NEON when IRQs are disabled
Explanation:
"To avoid having to preserve/restore kernel mode NEON state when
such a softirq is taken softirqs are now disabled when using the
NEON from task context."
should explain that it's nested kernel mode.
In other words, softirqs from user mode are fine, because the context
will be preserved. softirqs from kernel mode may be from a context
that has already saved the user NEON state, and thus we would need to
preserve the NEON state for the parent kernel mode context, and this
we don't allow.
The problem occurs when the kernel context disables hard IRQs, and
then uses NEON. When it's finished, and restores the userspace NEON
state, we call local_bh_enable() with hard IRQs disabled, which
causes a warning.
This commit addresses that by disallowing the use of NEON with hard
IRQs disabled.
https://lore.kernel.org/all/20250516231858.27899-4-ebiggers@kernel.org/T/#m104841b6e9346b1814c8b0fb9f2340551b0cd3e8
has some further context
* tag 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/rmk/linux:
ARM: 9446/1: Disallow kernel mode NEON when IRQs are disabled
ARM: 9447/1: arm/memremap: fix arch_memremap_can_ram_remap()
aef7457540