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arm64/sve: Clarify vq map semantics

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Currently the meanings of sve_vq_map and the ancillary helpers
__bit_to_vq() and __vq_to_bit() are not clearly explained.

This patch makes the explanatory comment clearer, and removes the
duplicate comment from fpsimd.h.

The WARN_ON() currently present in __bit_to_vq() confuses the
intended use of this helper.  Since these are low-level helpers not
intended for general-purpose use anyway, it is better not to make
guesses about how these functions will be used: rather, this patch
removes the WARN_ON() and relies on callers to use the helpers
sensibly.

Suggested-by: Andrew Jones <drjones@redhat.com>
Signed-off-by: Dave Martin <Dave.Martin@arm.com>
Reviewed-by: Andrew Jones <drjones@redhat.com>
Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
This commit is contained in:
Dave Martin 2019-04-11 16:53:18 +01:00 committed by Marc Zyngier
parent 5d8d4af244
commit 624835abf9
2 changed files with 6 additions and 5 deletions
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4
arch/arm64/include/asm/fpsimd.h
View File

@ -92,7 +92,6 @@ extern u64 read_zcr_features(void);
extern int __ro_after_init sve_max_vl;
extern int __ro_after_init sve_max_virtualisable_vl;
/* Set of available vector lengths, as vq_to_bit(vq): */
extern __ro_after_init DECLARE_BITMAP(sve_vq_map, SVE_VQ_MAX);
/*
@ -107,9 +106,6 @@ static inline unsigned int __vq_to_bit(unsigned int vq)
static inline unsigned int __bit_to_vq(unsigned int bit)
{
if (WARN_ON(bit >= SVE_VQ_MAX))
bit = SVE_VQ_MAX - 1;
return SVE_VQ_MAX - bit;
}

7
arch/arm64/kernel/fpsimd.c
View File

@ -135,10 +135,15 @@ static int sve_default_vl = -1;
/* Maximum supported vector length across all CPUs (initially poisoned) */
int __ro_after_init sve_max_vl = SVE_VL_MIN;
int __ro_after_init sve_max_virtualisable_vl = SVE_VL_MIN;
/* Set of available vector lengths, as vq_to_bit(vq): */
/*
* Set of available vector lengths,
* where length vq encoded as bit __vq_to_bit(vq):
*/
__ro_after_init DECLARE_BITMAP(sve_vq_map, SVE_VQ_MAX);
/* Set of vector lengths present on at least one cpu: */
static __ro_after_init DECLARE_BITMAP(sve_vq_partial_map, SVE_VQ_MAX);
static void __percpu *efi_sve_state;
#else /* ! CONFIG_ARM64_SVE */