linux-kernel - RE: :Re: [PATCH v2 04/19] crypto: x86/sha

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Message-ID: <MW5PR84MB18425B011CA1E206921DD539AB259@MW5PR84MB1842.NAMPRD84.PROD.OUTLOOK.COM>
Date:   Thu, 13 Oct 2022 22:41:58 +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: :Re: [PATCH v2 04/19] crypto: x86/sha - limit FPU preemption



> > diff --git a/arch/x86/crypto/sha1_ssse3_glue.c
...
> > +	do {
> > +		unsigned int chunk = min(len, FPU_BYTES);
> > +
> > +		if (chunk) {
> > +			kernel_fpu_begin();
> > +			sha1_base_do_update(desc, data, chunk, sha1_xform);
> > +			kernel_fpu_end();
> > +		}
> > +
> > +		len -= chunk;
> > +		data += chunk;
> > +	} while (len);
> 
> 'len' can't be 0 at the beginning of this loop, so the 'if (chunk)' check
> isn't needed.  And it wouldn't make sense even if 'len' could be 0, since
> a while loop could just be used in that case.

Thanks, I'll remove that if from all the sha functions, since they do
have that protective check upfront. I'll review the 0 byte handling in
all of them.