linux-kernel - Re: [PATCH v11 3/3] crypto: Add Inside Secure SafeXcel EIP-93 crypto engine support

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Message-ID: <Z-vGkbmX2PQ_gt7Z@gondor.apana.org.au>
Date: Tue, 1 Apr 2025 18:57:21 +0800
From: Herbert Xu <herbert@...dor.apana.org.au>
To: "Christian Marangi (Ansuel)" <ansuelsmth@...il.com>
Cc: "David S. Miller" <davem@...emloft.net>, Rob Herring <robh@...nel.org>,
	Krzysztof Kozlowski <krzk+dt@...nel.org>,
	Conor Dooley <conor+dt@...nel.org>,
	Antoine Tenart <atenart@...nel.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Ingo Molnar <mingo@...hat.com>, Will Deacon <will@...nel.org>,
	Waiman Long <longman@...hat.com>, Boqun Feng <boqun.feng@...il.com>,
	Nathan Chancellor <nathan@...nel.org>,
	Nick Desaulniers <ndesaulniers@...gle.com>,
	Bill Wendling <morbo@...gle.com>,
	Justin Stitt <justinstitt@...gle.com>, linux-crypto@...r.kernel.org,
	devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
	llvm@...ts.linux.dev, upstream@...oha.com,
	Richard van Schagen <vschagen@...oud.com>
Subject: Re: [PATCH v11 3/3] crypto: Add Inside Secure SafeXcel EIP-93 crypto
 engine support

On Tue, Apr 01, 2025 at 12:54:05PM +0200, Christian Marangi (Ansuel) wrote:
> Il giorno mar 1 apr 2025 alle ore 12:08 Herbert Xu
> <herbert@...dor.apana.org.au> ha scritto:
> >
> > On Tue, Jan 14, 2025 at 01:36:36PM +0100, Christian Marangi wrote:
> > >
> > > +static int eip93_send_hash_req(struct crypto_async_request *async, u8 *data,
> > > +                            dma_addr_t *data_dma, u32 len, bool last)
> > > +{
> >
> > ...
> >
> > > +again:
> > > +     ret = eip93_put_descriptor(eip93, &cdesc);
> > > +     if (ret) {
> > > +             usleep_range(EIP93_RING_BUSY_DELAY,
> > > +                          EIP93_RING_BUSY_DELAY * 2);
> > > +             goto again;
> > > +     }
> > > +
> > > +     /* Writing new descriptor count starts DMA action */
> > > +     writel(1, eip93->base + EIP93_REG_PE_CD_COUNT);
> >
> > Why is there no locking here? Shouldn't this be under ring->write_lock?
> >
> 
> Hi Herbert,
> this is really to tell DMA that there is new packet to process and
> gets decreased instantly.
> The lock is used to track what descriptor index should be used in the
> ring in the put and get
> functions.

AFAICS it's not safe to call eip93_put_descriptor simultaneously
since it doesn't use atomics.  Without locking in eip93_send_hash_req
two threads hashing into two separate eip93 requests will be calling
eip93_put_descriptor at the same time.

Cheers,
-- 
Email: Herbert Xu <herbert@...dor.apana.org.au>
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt