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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
159 lines
4.4 KiB
C
159 lines
4.4 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_H_
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#define __XEN_DRM_FRONT_H_
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#include <drm/drmP.h>
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#include <drm/drm_simple_kms_helper.h>
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#include <linux/scatterlist.h>
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#include "xen_drm_front_cfg.h"
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/**
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* DOC: Driver modes of operation in terms of display buffers used
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*
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* Depending on the requirements for the para-virtualized environment, namely
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* requirements dictated by the accompanying DRM/(v)GPU drivers running in both
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* host and guest environments, display buffers can be allocated by either
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* frontend driver or backend.
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*/
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/**
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* DOC: Buffers allocated by the frontend driver
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*
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* In this mode of operation driver allocates buffers from system memory.
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*
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* Note! If used with accompanying DRM/(v)GPU drivers this mode of operation
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* may require IOMMU support on the platform, so accompanying DRM/vGPU
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* hardware can still reach display buffer memory while importing PRIME
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* buffers from the frontend driver.
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*/
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/**
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* DOC: Buffers allocated by the backend
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*
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* This mode of operation is run-time configured via guest domain configuration
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* through XenStore entries.
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*
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* For systems which do not provide IOMMU support, but having specific
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* requirements for display buffers it is possible to allocate such buffers
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* at backend side and share those with the frontend.
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* For example, if host domain is 1:1 mapped and has DRM/GPU hardware expecting
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* physically contiguous memory, this allows implementing zero-copying
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* use-cases.
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*
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* Note, while using this scenario the following should be considered:
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*
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* #. If guest domain dies then pages/grants received from the backend
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* cannot be claimed back
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*
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* #. Misbehaving guest may send too many requests to the
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* backend exhausting its grant references and memory
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* (consider this from security POV)
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*/
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/**
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* DOC: Driver limitations
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*
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* #. Only primary plane without additional properties is supported.
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*
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* #. Only one video mode per connector supported which is configured
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* via XenStore.
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*
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* #. All CRTCs operate at fixed frequency of 60Hz.
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*/
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/* timeout in ms to wait for backend to respond */
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#define XEN_DRM_FRONT_WAIT_BACK_MS 3000
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#ifndef GRANT_INVALID_REF
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/*
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* Note on usage of grant reference 0 as invalid grant reference:
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* grant reference 0 is valid, but never exposed to a PV driver,
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* because of the fact it is already in use/reserved by the PV console.
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*/
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#define GRANT_INVALID_REF 0
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#endif
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struct xen_drm_front_info {
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struct xenbus_device *xb_dev;
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struct xen_drm_front_drm_info *drm_info;
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/* to protect data between backend IO code and interrupt handler */
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spinlock_t io_lock;
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int num_evt_pairs;
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struct xen_drm_front_evtchnl_pair *evt_pairs;
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struct xen_drm_front_cfg cfg;
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/* display buffers */
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struct list_head dbuf_list;
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};
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struct xen_drm_front_drm_pipeline {
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struct xen_drm_front_drm_info *drm_info;
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int index;
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struct drm_simple_display_pipe pipe;
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struct drm_connector conn;
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/* These are only for connector mode checking */
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int width, height;
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struct drm_pending_vblank_event *pending_event;
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struct delayed_work pflip_to_worker;
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bool conn_connected;
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};
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struct xen_drm_front_drm_info {
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struct xen_drm_front_info *front_info;
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struct drm_device *drm_dev;
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struct xen_drm_front_drm_pipeline pipeline[XEN_DRM_FRONT_MAX_CRTCS];
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};
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static inline u64 xen_drm_front_fb_to_cookie(struct drm_framebuffer *fb)
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{
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return (u64)fb;
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}
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static inline u64 xen_drm_front_dbuf_to_cookie(struct drm_gem_object *gem_obj)
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{
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return (u64)gem_obj;
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}
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int xen_drm_front_mode_set(struct xen_drm_front_drm_pipeline *pipeline,
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u32 x, u32 y, u32 width, u32 height,
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u32 bpp, u64 fb_cookie);
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int xen_drm_front_dbuf_create(struct xen_drm_front_info *front_info,
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u64 dbuf_cookie, u32 width, u32 height,
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u32 bpp, u64 size, struct page **pages);
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int xen_drm_front_fb_attach(struct xen_drm_front_info *front_info,
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u64 dbuf_cookie, u64 fb_cookie, u32 width,
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u32 height, u32 pixel_format);
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int xen_drm_front_fb_detach(struct xen_drm_front_info *front_info,
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u64 fb_cookie);
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int xen_drm_front_page_flip(struct xen_drm_front_info *front_info,
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int conn_idx, u64 fb_cookie);
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void xen_drm_front_on_frame_done(struct xen_drm_front_info *front_info,
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int conn_idx, u64 fb_cookie);
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#endif /* __XEN_DRM_FRONT_H_ */
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