linux-kernel - Re: [PATCH v1] crypto: iaa - Fix IAA disabling that occurs when sync

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Message-ID: <Z2_md-qdzb4b77gy@gondor.apana.org.au>
Date: Sat, 28 Dec 2024 19:52:23 +0800
From: Herbert Xu <herbert@...dor.apana.org.au>
To: Kanchana P Sridhar <kanchana.p.sridhar@...el.com>
Cc: linux-kernel@...r.kernel.org, linux-mm@...ck.org, hannes@...xchg.org,
	yosryahmed@...gle.com, nphamcs@...il.com, chengming.zhou@...ux.dev,
	usamaarif642@...il.com, ryan.roberts@....com, 21cnbao@...il.com,
	akpm@...ux-foundation.org, linux-crypto@...r.kernel.org,
	davem@...emloft.net, clabbe@...libre.com, ardb@...nel.org,
	ebiggers@...gle.com, surenb@...gle.com, kristen.c.accardi@...el.com,
	wajdi.k.feghali@...el.com, vinodh.gopal@...el.com,
	kanchana.p.sridhar@...el.com
Subject: Re: [PATCH v1] crypto: iaa - Fix IAA disabling that occurs when
 sync_mode is set to 'async'.

Kanchana P Sridhar <kanchana.p.sridhar@...el.com> wrote:
> With the latest mm-unstable, setting the iaa_crypto sync_mode to 'async'
> causes crypto testmgr.c test_acomp() failure and dmesg call traces, and
> zswap being unable to use 'deflate-iaa' as a compressor:
> 
> echo async > /sys/bus/dsa/drivers/crypto/sync_mode
> 
> [  255.271030] zswap: compressor deflate-iaa not available
> [  369.960673] INFO: task cryptomgr_test:4889 blocked for more than 122 seconds.
> [  369.970127]       Not tainted 6.13.0-rc1-mm-unstable-12-16-2024+ #324
> [  369.977411] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
> [  369.986246] task:cryptomgr_test  state:D stack:0     pid:4889  tgid:4889  ppid:2      flags:0x00004000
> [  369.986253] Call Trace:
> [  369.986256]  <TASK>
> [  369.986260]  __schedule+0x45c/0xfa0
> [  369.986273]  schedule+0x2e/0xb0
> [  369.986277]  schedule_timeout+0xe7/0x100
> [  369.986284]  ? __prepare_to_swait+0x4e/0x70
> [  369.986290]  wait_for_completion+0x8d/0x120
> [  369.986293]  test_acomp+0x284/0x670
> [  369.986305]  ? __pfx_cryptomgr_test+0x10/0x10
> [  369.986312]  alg_test_comp+0x263/0x440
> [  369.986315]  ? sched_balance_newidle+0x259/0x430
> [  369.986320]  ? __pfx_cryptomgr_test+0x10/0x10
> [  369.986323]  alg_test.part.27+0x103/0x410
> [  369.986326]  ? __schedule+0x464/0xfa0
> [  369.986330]  ? __pfx_cryptomgr_test+0x10/0x10
> [  369.986333]  cryptomgr_test+0x20/0x40
> [  369.986336]  kthread+0xda/0x110
> [  369.986344]  ? __pfx_kthread+0x10/0x10
> [  369.986346]  ret_from_fork+0x2d/0x40
> [  369.986355]  ? __pfx_kthread+0x10/0x10
> [  369.986358]  ret_from_fork_asm+0x1a/0x30
> [  369.986365]  </TASK>
> 
> This happens because the only async polling without interrupts that
> iaa_crypto currently implements is with the 'sync' mode. With 'async',
> iaa_crypto calls to compress/decompress submit the descriptor and return
> -EINPROGRESS, without any mechanism in the driver to poll for
> completions. Hence callers such as test_acomp() in crypto/testmgr.c or
> zswap, that wrap the calls to crypto_acomp_compress() and
> crypto_acomp_decompress() in synchronous wrappers, will block
> indefinitely. Even before zswap can notice this problem, the crypto
> testmgr.c's test_acomp() will fail and prevent registration of
> "deflate-iaa" as a valid crypto acomp algorithm, thereby disallowing the
> use of "deflate-iaa" as a zswap compress (zswap will fall-back to the
> default compressor in this case).
> 
> To fix this issue, this patch modifies the iaa_crypto sync_mode set
> function to treat 'async' equivalent to 'sync', so that the correct and
> only supported driver async polling without interrupts implementation is
> enabled, and zswap can use 'deflate-iaa' as the compressor.
> 
> Hence, with this patch, this is what will happen:
> 
> echo async > /sys/bus/dsa/drivers/crypto/sync_mode
> cat /sys/bus/dsa/drivers/crypto/sync_mode
> sync
> 
> There are no crypto/testmgr.c test_acomp() errors, no call traces and zswap
> can use 'deflate-iaa' without any errors. The iaa_crypto documentation has
> also been updated to mention this caveat with 'async' and what to expect
> with this fix.
> 
> True iaa_crypto async polling without interrupts is enabled in patch
> "crypto: iaa - Implement batch_compress(), batch_decompress() API in
> iaa_crypto." [1] which is under review as part of the "zswap IAA compress
> batching" patch-series [2]. Until this is merged, we would appreciate it if
> this current patch can be considered for a hotfix.
> 
> [1]: https://patchwork.kernel.org/project/linux-mm/patch/20241221063119.29140-5-kanchana.p.sridhar@intel.com/
> [2]: https://patchwork.kernel.org/project/linux-mm/list/?series=920084
> 
> Fixes: 09646c98d ("crypto: iaa - Add irq support for the crypto async interface")
> Signed-off-by: Kanchana P Sridhar <kanchana.p.sridhar@...el.com>
> ---
> Documentation/driver-api/crypto/iaa/iaa-crypto.rst | 9 ++++++++-
> drivers/crypto/intel/iaa/iaa_crypto_main.c         | 2 +-
> 2 files changed, 9 insertions(+), 2 deletions(-)

Patch applied.  Thanks.
-- 
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