svn commit: r289834 - head/sys/x86/x86

[Adrian Chadd]

Hi,

I've started seeing panics on -head with ATA code doing a dmamap load
-> panic. I'll test by reverting this patch and see what happens, but
when it /does/ happen I can't get a crashdump, so debugging will be
less easy.

Has anyone else seen this?


-a


On 23 October 2015 at 08:46, Roger Pau Monné <roger.pau at citrix.com> wrote:
> El 23/10/15 a les 17.39, Roger Pau Monné ha escrit:
>> Author: royger
>> Date: Fri Oct 23 15:39:59 2015
>> New Revision: 289834
>> URL: https://svnweb.freebsd.org/changeset/base/289834
>>
>> Log:
>>   x86/dma_bounce: rework _bus_dmamap_load_ma implementation
>>
>>   The implementation of bus_dmamap_load_ma_triv currently calls
>>   _bus_dmamap_load_phys on each page that is part of the passed in buffer.
>>   Since each page is treated as an individual buffer, the resulting behaviour
>>   is different from the behaviour of _bus_dmamap_load_buffer. This breaks
>>   certain drivers, like Xen blkfront.
>>
>>   If an unmapped buffer of size 4096 that starts at offset 13 into the first
>>   page is passed to the current _bus_dmamap_load_ma implementation (so the ma
>>   array contains two pages), the result is that two segments are created, one
>>   with a size of 4083 and the other with size 13 (because two independant
>>   calls to _bus_dmamap_load_phys are performed, one for each physical page).
>>   If the same is done with a mapped buffer and calling _bus_dmamap_load_buffer
>>   the result is that only one segment is created, with a size of 4096.
>>
>>   This patch relegates the usage of bus_dmamap_load_ma_triv in x86 bounce
>>   buffer code to drivers requesting BUS_DMA_KEEP_PG_OFFSET and implements
>>   _bus_dmamap_load_ma so that it's behaviour is the same as the mapped version
>>   (_bus_dmamap_load_buffer). This patch only modifies the x86 bounce buffer
>>   code, other arches are left untouched.
>>
>>   Reviewed by:                kib, jah
>>   Differential Revision:      https://reviews.freebsd.org/D888
>>   Sponsored by:               Citrix Systems R&D
>
> Forgot to add:
>
> MFC after:      2 weeks
>
> Roger.
>