arm64: cpufeatures: Correctly handle signed values

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Although we've had signed values for some features such as PMUv3
and FP, the code that handles the comparaison with some limit
has a couple of annoying issues:

- the min_field_value is always unsigned, meaning that we cannot
  easily compare it with a negative value

- it is not possible to have a range of values, let alone a range
  of negative values

Fix this by:

- adding an upper limit to the comparison, defaulting to all bits
  being set to the maximum positive value

- ensuring that the signess of the min and max values are taken into
  account

A ARM64_CPUID_FIELDS_NEG() macro is provided for signed features, but
nothing is using it yet.

Signed-off-by: Marc Zyngier <maz@kernel.org>
Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
Link: https://lore.kernel.org/r/20240122181344.258974-3-maz@kernel.org
Signed-off-by: Oliver Upton <oliver.upton@linux.dev>

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This commit is contained in:

Marc Zyngier 2024-01-22 18:13:36 +00:00 • committed by Oliver Upton

parent 53eaeb7fbe

commit d9a065914d

2 changed files with 57 additions and 9 deletions

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arch/arm64/include/asm/cpufeature.h

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65

arch/arm64/kernel/cpufeature.c

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