Date: Fri, 23 Oct 2015 17:46:21 +0200 From: =?UTF-8?Q?Roger_Pau_Monn=c3=a9?= <roger.pau@citrix.com> To: =?UTF-8?Q?Roger_Pau_Monn=c3=a9?= <royger@FreeBSD.org>, <src-committers@freebsd.org>, <svn-src-all@freebsd.org>, <svn-src-head@freebsd.org> Subject: Re: svn commit: r289834 - head/sys/x86/x86 Message-ID: <562A564D.9080703@citrix.com> In-Reply-To: <201510231539.t9NFdxPe018130@repo.freebsd.org> References: <201510231539.t9NFdxPe018130@repo.freebsd.org>
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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.
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