Hi! On Fri, May 09, 2025 at 10:33:08PM -0700, Eric Biggers wrote: > On Sat, May 10, 2025 at 01:10:22PM +0800, Herbert Xu wrote: > > On Fri, May 09, 2025 at 09:44:50PM -0700, Eric Biggers wrote: > > > > > > This fixes "-cpu Power10", but older CPUs (e.g. "-cpu POWER9") are still > > > failing. > > > > You're right. I'll revert this and apply the following patch > > instead. > > > > BTW this thing is still hopelessly broken if it's called from > > softirq context because there is no SIMD fallback. Yes I removed > > the SIMD check but it was already broken before that as it simply > > switched from the 4-block version to the 1-block version if SIMD > > is not available rather than actually doing something that is > > safe in softirq context. > > > > Perhaps we should just remove this altogether until it's fixed. > > Yes, the PowerPC Poly1305 code incorrectly uses VSX without first checking > crypto_simd_usable(). And PowerPC also doesn't support VSX in softirqs, or at > least it doesn't claim to (it doesn't override may_use_simd(), so it gets the > default from include/asm-generic/simd.h which returns false in softirq > context). > Maybe add 'depends on BROKEN' to CRYPTO_POLY1305_P10 for now, and give the > PowerPC folks (Cc'ed) a chance to fix this before removing the code.
What doe "may_use_simd" even *mean*? At its declaration site it says "whether it is allowable at this time to issue SIMD instructions or access the SIMD register file", but that is 100% meaningless, you can do SIMD in GPRs. On PowerPC we have two separate register files dedicated to SIMD-like stuff, the VMX and the VSX register files. Which of those is this function supposed to care about? It looks like the whole "may_use_simd" thing is a misguided abstraction unfortunately :-( Segher
