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4394e96423
It turns out this was only needed to paper over a bug in the CMA
helpers, which was addressed in
commit 998fb1a0f4
Author: Liviu Dudau <Liviu.Dudau@arm.com>
Date: Fri Nov 10 13:33:10 2017 +0000
drm: gem_cma_helper.c: Allow importing of contiguous scatterlists with nents > 1
Without this the following pipeline didn't work:
domU:
1. xen-front allocates a non-contig buffer
2. creates grants out of it
dom0:
3. converts the grants into a dma-buf. Since they're non-contig, the
scatter-list is huge.
4. imports it into rcar-du, which requires dma-contig memory for
scanout.
-> On this given platform there's an IOMMU, so in theory this should
work. But in practice this failed, because of the huge number of sg
entries, even though the IOMMU driver mapped it all into a dma-contig
range.
With a guest-contig buffer allocated in step 1, this problem doesn't
exist. But there's technically no reason to require guest-contig
memory for xen buffer sharing using grants.
Given all that, the xen-front cma support is not needed and should be
removed.
Signed-off-by: Oleksandr Andrushchenko <oleksandr_andrushchenko@epam.com>
Suggested-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Acked-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: https://patchwork.freedesktop.org/patch/msgid/20180417074012.21311-1-andr2000@gmail.com
65 lines
1.7 KiB
C
65 lines
1.7 KiB
C
/* SPDX-License-Identifier: GPL-2.0 OR MIT */
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/*
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* Xen para-virtual DRM device
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*
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* Copyright (C) 2016-2018 EPAM Systems Inc.
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*
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* Author: Oleksandr Andrushchenko <oleksandr_andrushchenko@epam.com>
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*/
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#ifndef __XEN_DRM_FRONT_SHBUF_H_
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#define __XEN_DRM_FRONT_SHBUF_H_
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#include <linux/kernel.h>
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#include <linux/scatterlist.h>
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#include <xen/grant_table.h>
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struct xen_drm_front_shbuf {
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/*
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* number of references granted for the backend use:
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* - for allocated/imported dma-buf's this holds number of grant
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* references for the page directory and pages of the buffer
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* - for the buffer provided by the backend this holds number of
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* grant references for the page directory as grant references for
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* the buffer will be provided by the backend
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*/
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int num_grefs;
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grant_ref_t *grefs;
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unsigned char *directory;
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int num_pages;
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struct page **pages;
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struct xenbus_device *xb_dev;
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/* these are the ops used internally depending on be_alloc mode */
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const struct xen_drm_front_shbuf_ops *ops;
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/* Xen map handles for the buffer allocated by the backend */
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grant_handle_t *backend_map_handles;
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};
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struct xen_drm_front_shbuf_cfg {
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struct xenbus_device *xb_dev;
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size_t size;
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struct page **pages;
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bool be_alloc;
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};
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struct xen_drm_front_shbuf *
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xen_drm_front_shbuf_alloc(struct xen_drm_front_shbuf_cfg *cfg);
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grant_ref_t xen_drm_front_shbuf_get_dir_start(struct xen_drm_front_shbuf *buf);
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int xen_drm_front_shbuf_map(struct xen_drm_front_shbuf *buf);
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int xen_drm_front_shbuf_unmap(struct xen_drm_front_shbuf *buf);
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void xen_drm_front_shbuf_flush(struct xen_drm_front_shbuf *buf);
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void xen_drm_front_shbuf_free(struct xen_drm_front_shbuf *buf);
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#endif /* __XEN_DRM_FRONT_SHBUF_H_ */
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