linux-kernel - RE: [PATCH v2 08/19] crypto: x86/ghash

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Date:   Thu, 13 Oct 2022 22:52:09 +0000
From:   "Elliott, Robert (Servers)" <elliott@....com>
To:     Eric Biggers <ebiggers@...nel.org>
CC:     "herbert@...dor.apana.org.au" <herbert@...dor.apana.org.au>,
        "davem@...emloft.net" <davem@...emloft.net>,
        "tim.c.chen@...ux.intel.com" <tim.c.chen@...ux.intel.com>,
        "ap420073@...il.com" <ap420073@...il.com>,
        "ardb@...nel.org" <ardb@...nel.org>,
        "linux-crypto@...r.kernel.org" <linux-crypto@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH v2 08/19] crypto: x86/ghash - limit FPU preemption



> > +	while (srclen >= GHASH_BLOCK_SIZE) {
> > +		unsigned int fpulen = min(srclen, FPU_BYTES);
> > +
> > +		kernel_fpu_begin();
> > +		while (fpulen >= GHASH_BLOCK_SIZE) {
> > +			int n = min_t(unsigned int, fpulen, GHASH_BLOCK_SIZE);
> > +
> > +			clmul_ghash_update(dst, src, n, &ctx->shash);
> > +
> > +			srclen -= n;
> > +			fpulen -= n;
> > +			src += n;
> > +		}
> > +		kernel_fpu_end();
> > +	}
> 
> Another loop that doesn't make sense.  Why is this only passing 16 bytes at a
> time into the assembly code?  There shouldn't be an inner loop here at all.

Thanks, copied the pattern from another function whose assembly function
had a size limit. clmul_ghash_update looks ready for all sizes, so I'll
simplify that.