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author | royger <royger@FreeBSD.org> | 2015-10-23 15:39:59 +0000 |
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committer | royger <royger@FreeBSD.org> | 2015-10-23 15:39:59 +0000 |
commit | c24a22103b562414262f25bf5a00d62fcfdbf28a (patch) | |
tree | bf17f8dd710ed5ad42bec7f409bd6b853488b280 /sbin/sysctl | |
parent | c9a1277fcf843fdfd32ade76c187d1ac052bdbfa (diff) | |
download | FreeBSD-src-c24a22103b562414262f25bf5a00d62fcfdbf28a.zip FreeBSD-src-c24a22103b562414262f25bf5a00d62fcfdbf28a.tar.gz |
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
Diffstat (limited to 'sbin/sysctl')
0 files changed, 0 insertions, 0 deletions