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Subject: Re: [PATCHv2] mtd: spi-nor: Fix Cadence QSPI page fault kernel panic
To:     thor.thayer@linux.intel.com, cyrille.pitchen@wedev4u.fr,
        dwmw2@infradead.org, computersforpeace@gmail.com,
        boris.brezillon@bootlin.com, richard@nod.at
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References: <1522073537-27386-1-git-send-email-thor.thayer@linux.intel.com>
 <0b460613-4ac2-c4d8-429e-248a4742a408@linux.intel.com>
From:   Marek Vasut <marek.vasut@gmail.com>
Message-ID: <c009725f-dbbc-d4b1-4f67-6cae7cdf6f05@gmail.com>
Date:   Wed, 11 Apr 2018 17:23:57 +0200
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On 04/11/2018 05:17 PM, Thor Thayer wrote:
> Hi. Any comments on this patch?

None other than

Reviewed-by: Marek Vasut <marek.vasut@gmail.com>

sorry for the delay.

btw stop top-posting please.

> On 03/26/2018 09:12 AM, thor.thayer@linux.intel.com wrote:
>> From: Thor Thayer <thor.thayer@linux.intel.com>
>>
>> The current Cadence QSPI driver caused a kernel panic when loading
>> a Root Filesystem from QSPI. The problem was caused by reading more
>> bytes than needed because the QSPI operated on 4 bytes at a time.
>> <snip>
>> [    7.947754] spi_nor_read[1048]:from 0x037cad74, len 1 [bfe07fff]
>> [    7.956247] cqspi_read[910]:offset 0x58502516, buffer=bfe07fff
>> [    7.956247]
>> [    7.966046] Unable to handle kernel paging request at virtual
>> address bfe08002
>> [    7.973239] pgd = eebfc000
>> [    7.975931] [bfe08002] *pgd=2fffb811, *pte=00000000, *ppte=00000000
>> </snip>
>> Notice above how only 1 byte needed to be read but by reading 4 bytes
>> into the end of a mapped page, an unrecoverable page fault occurred.
>>
>> This patch uses a temporary buffer to hold the 4 bytes read and then
>> copies only the bytes required into the buffer. A min() function is
>> used to limit the length to prevent buffer overflows.
>>
>> Request testing of this patch on other platforms. This was tested
>> on the Intel Arria10 SoCFPGA DevKit.
>>
>> Signed-off-by: Thor Thayer <thor.thayer@linux.intel.com>

[...]


-- 
Best regards,
Marek Vasut