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Date: Mon, 3 Jun 2024 17:28:56 +0900
From: Sergey Senozhatsky <senozhatsky@chromium.org>
To: Herbert Xu <herbert@gondor.apana.org.au>
Cc: Linux Crypto Mailing List <linux-crypto@vger.kernel.org>,
	Sergey Senozhatsky <senozhatsky@chromium.org>
Subject: Re: [PATCH 1/3] crypto: scomp - Add setparam interface
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On (24/06/03 11:34), Sergey Senozhatsky wrote:
> On (24/06/01 11:54), Herbert Xu wrote:
> > On Sat, Jun 01, 2024 at 09:24:15AM +0900, Sergey Senozhatsky wrote:
> > >
> > > Is it possible to share a tfm? I thought that tfm-s carry some state
> > > (compression workmem/scratch buffer) so one cannot do parallel compressions
> > > on different CPUs using the same tfm.
> > 
> > Yes the tfm can be shared.  The data state is kept in the request
> > object.
> 
> Oh, nice, thanks.

Herbert, I'm not sure I see how tfm sharing is working.

crypto_tfm carries a pointer to __crt_ctx, which e.g. for zstd
is struct zstd_ctx, where it keeps all the state (zstd_cctx, zstd_dctx,
and compression/decompression workmem buffers).

When we call crypto_comp_compress()->zstd_compress() we just pass tfm,
then the driver gets tfm-s state/ctx via crypto_tfm_ctx() and uses it
for underlying compression library call.