From: Nicolas Morey-Chaisemartin <nmorey@kalray.eu>
To: One Thousand Gnomes <gnomes@lxorguk.ukuu.org.uk>
Cc: linux-kernel@vger.kernel.org
Subject: Re: [Question] Missing data after DMA read transfer
Date: Thu, 21 Apr 2016 10:51:52 +0200 [thread overview]
Message-ID: <278aff83-5d3a-e755-a4c3-50bfccf08886@kalray.eu> (raw)
In-Reply-To: <20160421093512.4a63e2c2@lxorguk.ukuu.org.uk>
Le 04/21/2016 à 10:35 AM, One Thousand Gnomes a écrit :
>> But if I try to copy_from_user (using the address coming from userland, the one passed to get_user_pages), the data has not been written and I see the memset value.
>>
>> I manage to build a test case that fails all the time, but never at the same offset within the buffer.
>> It's always in the middle (never at the start nor end), for a few pages long (varies between runs).
> Always page aligned, always cache line aligned or arbitrarily aligned ?
>
> Alan
It's always page aligned for both start and end (meaning last "untransferred" byte is the last byte of a page)
Nicolas
next prev parent reply other threads:[~2016-04-21 8:51 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-04-20 14:56 Nicolas Morey-Chaisemartin
2016-04-21 8:35 ` One Thousand Gnomes
2016-04-21 8:51 ` Nicolas Morey-Chaisemartin [this message]
2016-04-25 6:18 ` Nicolas Morey-Chaisemartin
2016-04-26 13:31 ` Nicolas Morey-Chaisemartin
2016-04-27 9:20 ` Nicolas Morey-Chaisemartin
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