Hi folks, I noticed that the ARM implementation [1] of chacha20 makes a check to may_use_simd(), but the ARM64 implementation [2] does not. Question 1: is this a bug, in which case I'll submit a patch shortly, or is this intentional? In case of the latter, could somebody explain the reasoning? On a similar note, the only ARM64 glue code that uses may_use_simd() is sha256; everything else does not. Shall I submit a substantial patch series to fix this up everywhere?
Secondly, I noticed that may_use_simd() is essentially aliased to !in_interrupt(), since it uses the asm-generic variety. Question 2: Isn't this overkill? Couldn't we make an arm/arm64 variant of this that only checks in_irq()? Lastly, APIs like pcrypts and padata execute with bottom halves disabled, even though their actual execution environment is process context, via a workqueue. Thus, here, in_interrupt() will always be true, even though this is likely a place where we want to use simd. Question 3: is there something better that could be done? Thanks, Jason [1] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/arch/arm/crypto/chacha20-neon-glue.c#n67 [2] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/arch/arm64/crypto/chacha20-neon-glue.c#n66
