From: Herbert Xu <herbert@gondor.apana.org.au>
Subject: Re: [PATCH stable 3.16+] crypto: s5p-sss - Fix missed interrupts
 when working with 8 kB blocks
Date: Tue, 31 May 2016 10:15:36 +0800
Message-ID: <20160531021536.GA11762@gondor.apana.org.au>
References: <1464602968-7526-1-git-send-email-k.kozlowski@samsung.com>
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Cc: stable@vger.kernel.org, linux-crypto@vger.kernel.org,
	linux-kernel@vger.kernel.org,
	Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>
To: Krzysztof Kozlowski <k.kozlowski@samsung.com>
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On Mon, May 30, 2016 at 12:09:28PM +0200, Krzysztof Kozlowski wrote:
> commit 79152e8d085fd64484afd473ef6830b45518acba upstream.
> 
> The tcrypt testing module on Exynos5422-based Odroid XU3/4 board failed on
> testing 8 kB size blocks:
> 
> 	$ sudo modprobe tcrypt sec=1 mode=500
> 	testing speed of async ecb(aes) (ecb-aes-s5p) encryption
> 	test 0 (128 bit key, 16 byte blocks): 21971 operations in 1 seconds (351536 bytes)
> 	test 1 (128 bit key, 64 byte blocks): 21731 operations in 1 seconds (1390784 bytes)
> 	test 2 (128 bit key, 256 byte blocks): 21932 operations in 1 seconds (5614592 bytes)
> 	test 3 (128 bit key, 1024 byte blocks): 21685 operations in 1 seconds (22205440 bytes)
> 	test 4 (128 bit key, 8192 byte blocks):
> 
> This was caused by a race issue of missed BRDMA_DONE ("Block cipher
> Receiving DMA") interrupt. Device starts processing the data in DMA mode
> immediately after setting length of DMA block: receiving (FCBRDMAL) or
> transmitting (FCBTDMAL). The driver sets these lengths from interrupt
> handler through s5p_set_dma_indata() function (or xxx_setdata()).
> 
> However the interrupt handler was first dealing with receive buffer
> (dma-unmap old, dma-map new, set receive block length which starts the
> operation), then with transmit buffer and finally was clearing pending
> interrupts (FCINTPEND). Because of the time window between setting
> receive buffer length and clearing pending interrupts, the operation on
> receive buffer could end already and driver would miss new interrupt.
> 
> User manual for Exynos5422 confirms in example code that setting DMA
> block lengths should be the last operation.
> 
> The tcrypt hang could be also observed in following blocked-task dmesg:
> 
> INFO: task modprobe:258 blocked for more than 120 seconds.
>       Not tainted 4.6.0-rc4-next-20160419-00005-g9eac8b7b7753-dirty #42
> "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
> modprobe        D c06b09d8     0   258    256 0x00000000
> [<c06b09d8>] (__schedule) from [<c06b0f24>] (schedule+0x40/0xac)
> [<c06b0f24>] (schedule) from [<c06b49f8>] (schedule_timeout+0x124/0x178)
> [<c06b49f8>] (schedule_timeout) from [<c06b17fc>] (wait_for_common+0xb8/0x144)
> [<c06b17fc>] (wait_for_common) from [<bf0013b8>] (test_acipher_speed+0x49c/0x740 [tcrypt])
> [<bf0013b8>] (test_acipher_speed [tcrypt]) from [<bf003e8c>] (do_test+0x2240/0x30ec [tcrypt])
> [<bf003e8c>] (do_test [tcrypt]) from [<bf008048>] (tcrypt_mod_init+0x48/0xa4 [tcrypt])
> [<bf008048>] (tcrypt_mod_init [tcrypt]) from [<c010177c>] (do_one_initcall+0x3c/0x16c)
> [<c010177c>] (do_one_initcall) from [<c0191ff0>] (do_init_module+0x5c/0x1ac)
> [<c0191ff0>] (do_init_module) from [<c0185610>] (load_module+0x1a30/0x1d08)
> [<c0185610>] (load_module) from [<c0185ab0>] (SyS_finit_module+0x8c/0x98)
> [<c0185ab0>] (SyS_finit_module) from [<c01078c0>] (ret_fast_syscall+0x0/0x3c)
> 
> Fixes: a49e490c7a8a ("crypto: s5p-sss - add S5PV210 advanced crypto engine support")
> Cc: <stable@vger.kernel.org> # 3.16+
> Signed-off-by: Krzysztof Kozlowski <k.kozlowski@samsung.com>
> Tested-by: Marek Szyprowski <m.szyprowski@samsung.com>
> Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
> [k.kozlowski: Backport to v3.16]

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