Message-ID: <20170428100836.GM3390@nuc-i3427.alporthouse.com>
Date:   Fri, 28 Apr 2017 11:08:36 +0100
From:   Chris Wilson <chris@...is-wilson.co.uk>
To:     Xiaoguang Chen <xiaoguang.chen@...el.com>
Cc:     kraxel@...hat.com, alex.williamson@...hat.com,
        intel-gfx@...ts.freedesktop.org,
        intel-gvt-dev@...ts.freedesktop.org, zhi.a.wang@...el.com,
        zhenyuw@...ux.intel.com, linux-kernel@...r.kernel.org,
        zhiyuan.lv@...el.com, kevin.tian@...el.com
Subject: Re: [Intel-gfx] [RFC PATCH 5/6] drm/i915/gvt: dmabuf support for
 GVT-g

On Fri, Apr 28, 2017 at 05:35:29PM +0800, Xiaoguang Chen wrote:
> dmabuf for GVT-g can be exported to users who can use the dmabuf to show
> the desktop of vm which use intel vgpu.
> 
> Currently we provide query and create new dmabuf operations.
> 
> Users of dmabuf can cache some created dmabufs and related information such
> as the framebuffer's address, size, tiling mode, width, height etc. When
> refresh the screen first query the currnet vgpu's frambuffer and compare
> with the cached ones(address, size, tiling, width, height etc) if found one
> then reuse the found dmabuf to gain performance improvment.
> 
> If there is no dmabuf created yet or not found in the cached dmabufs then
> need to create a new dmabuf. To create a dmabuf first a gem object will
> be created and the backing storage of this gem object is the vgpu's
> framebuffer(primary/cursor). Then associate this gem object to a dmabuf
> and export this dmabuf. A file descriptor will be generated for this dmabuf
> and this file descriptor can be sent to user space to do display.
> 
> Signed-off-by: Xiaoguang Chen <xiaoguang.chen@...el.com>
> ---
>  drivers/gpu/drm/i915/gvt/Makefile |   2 +-
>  drivers/gpu/drm/i915/gvt/dmabuf.c | 268 ++++++++++++++++++++++++++++++++++++++
>  drivers/gpu/drm/i915/gvt/dmabuf.h |  50 +++++++
>  drivers/gpu/drm/i915/gvt/gvt.h    |   1 +
>  4 files changed, 320 insertions(+), 1 deletion(-)
>  create mode 100644 drivers/gpu/drm/i915/gvt/dmabuf.c
>  create mode 100644 drivers/gpu/drm/i915/gvt/dmabuf.h
> 
> diff --git a/drivers/gpu/drm/i915/gvt/Makefile b/drivers/gpu/drm/i915/gvt/Makefile
> index 192ca26..e480f7d 100644
> --- a/drivers/gpu/drm/i915/gvt/Makefile
> +++ b/drivers/gpu/drm/i915/gvt/Makefile
> @@ -2,7 +2,7 @@ GVT_DIR := gvt
>  GVT_SOURCE := gvt.o aperture_gm.o handlers.o vgpu.o trace_points.o firmware.o \
>  	interrupt.o gtt.o cfg_space.o opregion.o mmio.o display.o edid.o \
>  	execlist.o scheduler.o sched_policy.o render.o cmd_parser.o \
> -	fb_decoder.o
> +	fb_decoder.o dmabuf.o
>  
>  ccflags-y				+= -I$(src) -I$(src)/$(GVT_DIR) -Wall
>  i915-y					+= $(addprefix $(GVT_DIR)/, $(GVT_SOURCE))
> diff --git a/drivers/gpu/drm/i915/gvt/dmabuf.c b/drivers/gpu/drm/i915/gvt/dmabuf.c
> new file mode 100644
> index 0000000..d776dfa
> --- /dev/null
> +++ b/drivers/gpu/drm/i915/gvt/dmabuf.c
> @@ -0,0 +1,268 @@
> +/*
> + * Copyright 2017 Intel Corporation. All rights reserved.
> + *
> + * Permission is hereby granted, free of charge, to any person obtaining a
> + * copy of this software and associated documentation files (the "Software"),
> + * to deal in the Software without restriction, including without limitation
> + * the rights to use, copy, modify, merge, publish, distribute, sublicense,
> + * and/or sell copies of the Software, and to permit persons to whom the
> + * Software is furnished to do so, subject to the following conditions:
> + *
> + * The above copyright notice and this permission notice (including the next
> + * paragraph) shall be included in all copies or substantial portions of the
> + * Software.
> + *
> + * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
> + * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
> + * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
> + * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
> + * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
> + * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
> + * DEALINGS IN THE SOFTWARE.
> + *
> + * Authors:
> + *    Zhiyuan Lv <zhiyuan.lv@...el.com>
> + *
> + * Contributors:
> + *    Xiaoguang Chen <xiaoguang.chen@...el.com>
> + */
> +
> +#include <linux/dma-buf.h>
> +#include <drm/drmP.h>
> +
> +#include "i915_drv.h"
> +#include "gvt.h"
> +
> +static struct sg_table *intel_vgpu_gem_get_pages(
> +		struct drm_i915_gem_object *obj)
> +{
> +	WARN_ON(1);
> +	return NULL;
> +}
> +
> +static void intel_vgpu_gem_put_pages(struct drm_i915_gem_object *obj,
> +		struct sg_table *pages)
> +{
> +	/* like stolen memory, this should only be called during free
> +	 * after clearing pin count.
> +	 */

Time to re-read how stolen works (see get_pages and pinning on
creation).

> +	sg_free_table(pages);
> +	kfree(pages);
> +}
> +
> +static const struct drm_i915_gem_object_ops intel_vgpu_gem_ops = {
> +	.get_pages = intel_vgpu_gem_get_pages,
> +	.put_pages = intel_vgpu_gem_put_pages,
> +};
> +
> +#define GEN8_DECODE_PTE(pte) \
> +	((dma_addr_t)(((((u64)pte) >> 12) & 0x7ffffffULL) << 12))
> +
> +#define GEN7_DECODE_PTE(pte) \
> +	((dma_addr_t)(((((u64)pte) & 0x7f0) << 28) | (u64)(pte & 0xfffff000)))
> +
> +static struct sg_table *
> +intel_vgpu_create_sg_pages(struct drm_device *dev, u32 start, u32 num_pages)
> +{
> +	struct drm_i915_private *dev_priv = dev->dev_private;
> +	struct sg_table *st;
> +	struct scatterlist *sg;
> +	int i;
> +	gen8_pte_t __iomem *gtt_entries;
> +
> +	st = kmalloc(sizeof(*st), GFP_KERNEL);
> +	if (st == NULL)
> +		return NULL;
> +
> +	if (sg_alloc_table(st, num_pages, GFP_KERNEL)) {
> +		kfree(st);
> +		return NULL;
> +	}
> +
> +	gtt_entries = (gen8_pte_t __iomem *)dev_priv->ggtt.gsm +
> +		(start >> PAGE_SHIFT);
> +	for_each_sg(st->sgl, sg, num_pages, i) {
> +		sg->offset = 0;
> +		sg->length = PAGE_SIZE;
> +		sg_dma_address(sg) =
> +			GEN8_DECODE_PTE(readq(&gtt_entries[i]));
> +		sg_dma_len(sg) = PAGE_SIZE;
> +	}

This should be get_pages.

> +	return st;
> +}
> +
> +static struct drm_i915_gem_object *intel_vgpu_create_gem(struct drm_device *dev,
> +		struct intel_vgpu_dmabuf *info)
> +{
> +	struct drm_i915_gem_object *obj;
> +	struct drm_i915_private *pri = dev->dev_private;
> +
> +	obj = i915_gem_object_alloc(pri);
> +	if (obj == NULL)
> +		return NULL;
> +
> +	drm_gem_private_object_init(dev, &obj->base, info->size << PAGE_SHIFT);
> +	i915_gem_object_init(obj, &intel_vgpu_gem_ops);
> +	obj->mm.pages = intel_vgpu_create_sg_pages(dev, info->start,
> +			info->size);
> +	if (obj->mm.pages == NULL) {
> +		i915_gem_object_free(obj);
> +		return NULL;
> +	}

Having created the obj, just call i915_gem_object_pin_pages(). Or better
yet, don't pin the pages upon creation and just defer it to first use -
which be very soon.

> +	obj->cache_level = I915_CACHE_L3_LLC;

Are you sure?


> +	if (IS_SKYLAKE(pri)) {
> +		unsigned int tiling_mode = 0;
> +
> +		switch (info->tiled << 10) {
> +		case PLANE_CTL_TILED_LINEAR:
> +			tiling_mode = I915_TILING_NONE;
> +			break;
> +		case PLANE_CTL_TILED_X:
> +			tiling_mode = I915_TILING_X;
> +			break;
> +		case PLANE_CTL_TILED_Y:
> +			tiling_mode = I915_TILING_Y;
> +			break;
> +		default:
> +			gvt_dbg_core("tile %d not supported\n", info->tiled);
> +		}
> +		obj->tiling_and_stride = tiling_mode | info->stride;

If tiling_mode == 0, stride must be zero. Is that enforced?

> +	} else {
> +		obj->tiling_and_stride = (info->tiled ? I915_TILING_X :
> +			I915_TILING_NONE) | (info->tiled ? info->stride : 0);

Rewrite this neatly.
Hint obj->tiling_and_stride starts as zero and you don't need to do any
of this if !tiled.

> +	}
> +
> +	return obj;
> +}
> +
> +static int intel_vgpu_get_plane_info(struct drm_device *dev,
> +		struct intel_vgpu *vgpu,
> +		struct intel_vgpu_dmabuf *info)
> +{
> +	struct drm_i915_private *dev_priv = dev->dev_private;
> +	struct intel_vgpu_primary_plane_format *p;
> +	struct intel_vgpu_cursor_plane_format *c;
> +
> +	if (info->plane_id == INTEL_GVT_PLANE_PRIMARY) {
> +		p = (struct intel_vgpu_primary_plane_format *)
> +			intel_vgpu_decode_plane(dev, vgpu, info->plane_id);
> +		if (p != NULL) {
> +			info->start = p->base;
> +			info->width = p->width;
> +			info->height = p->height;
> +			info->stride = p->stride;
> +			info->drm_format = p->drm_format;
> +			info->tiled = p->tiled;
> +			info->size = (((p->stride * p->height * p->bpp) / 8) +
> +					(PAGE_SIZE - 1)) >> PAGE_SHIFT;
> +		} else {
> +			gvt_dbg_core("invalid primary plane\n");
> +			return -EINVAL;
> +		}
> +	} else if (info->plane_id == INTEL_GVT_PLANE_CURSOR) {
> +		c = (struct intel_vgpu_cursor_plane_format *)
> +			intel_vgpu_decode_plane(dev, vgpu, info->plane_id);
> +		if (c != NULL) {
> +			info->start = c->base;
> +			info->width = c->width;
> +			info->height = c->height;
> +			info->stride = c->width * (c->bpp / 8);
> +			info->tiled = 0;
> +			info->x_pos = c->x_pos;
> +			info->y_pos = c->y_pos;
> +			info->size = (((info->stride * c->height * c->bpp) / 8) +
> +					(PAGE_SIZE - 1)) >> PAGE_SHIFT;
> +		} else {
> +			gvt_dbg_core("invalid cursor plane\n");
> +			return -EINVAL;
> +		}
> +	} else {
> +		gvt_vgpu_err("invalid plane id:%d\n", info->plane_id);
> +		return -EINVAL;
> +	}
> +
> +	if (info->start & (PAGE_SIZE - 1)) {
> +		gvt_vgpu_err("Not aligned fb address:0x%x\n", info->start);
> +		return -EINVAL;
> +	}
> +	if (((info->start >> PAGE_SHIFT) + info->size) >
> +		ggtt_total_entries(&dev_priv->ggtt)) {
> +		gvt_vgpu_err("Invalid GTT offset or size\n");
> +		return -EINVAL;
> +	}
> +
> +	return 0;
> +}
> +
> +static struct drm_i915_gem_object *intel_vgpu_create_gem_from_vgpuid(
> +		struct drm_device *dev, struct intel_vgpu *vgpu,
> +		struct intel_vgpu_dmabuf *info)
> +{
> +	struct drm_i915_gem_object *obj;
> +	int ret;
> +
> +	ret = intel_vgpu_get_plane_info(dev, vgpu, info);
> +	if (ret) {
> +		gvt_vgpu_err("get plane info failed:%d\n", info->plane_id);
> +		return NULL;

Propagate errors.

> +	}
> +	obj = intel_vgpu_create_gem(dev, info);
> +
> +	return obj;
> +}
> +
> +int intel_vgpu_query_dmabuf(struct intel_vgpu *vgpu, void *args)
> +{
> +	struct drm_device *dev = &vgpu->gvt->dev_priv->drm;
> +	int ret;
> +	struct intel_vgpu_dmabuf *info = args;
> +
> +	ret = intel_vgpu_get_plane_info(dev, vgpu, info);
> +	if (ret) {
> +		gvt_vgpu_err("get plane info failed:%d\n", info->plane_id);
> +		return -EINVAL;
> +	}
> +
> +	return 0;
> +}
> +
> +int intel_vgpu_generate_dmabuf(struct intel_vgpu *vgpu, void *args)
> +{
> +	struct dma_buf *dmabuf;
> +	struct drm_i915_gem_object *obj;
> +	struct drm_device *dev = &vgpu->gvt->dev_priv->drm;
> +	int ret;
> +	struct intel_vgpu_dmabuf *info = args;
> +	struct dma_buf_export_info exp_info = {
> +		.exp_name = KBUILD_MODNAME,
> +		.owner = THIS_MODULE };
> +
> +	obj = intel_vgpu_create_gem_from_vgpuid(dev, vgpu, info);
> +	if (obj == NULL) {
> +		gvt_vgpu_err("create gvt gem obj failed:%d\n", vgpu->id);
> +		return -EINVAL;
> +	}
> +
> +	exp_info.ops = &i915_dmabuf_ops;

Please put back my private i915_dmabuf_ops from where you stole it from.

Just call dmabuf = i915_gem_prime_export(dev, obj, DRM_CLOEXEC | DRM_RDWR);

> +	exp_info.size = obj->base.size;
> +	exp_info.flags = DRM_CLOEXEC | DRM_RDWR;
> +	exp_info.priv = &obj->base;
> +	exp_info.resv = obj->resv;
> +
> +	dmabuf = drm_gem_dmabuf_export(dev, &exp_info);
> +	if (IS_ERR(dmabuf)) {
> +		gvt_vgpu_err("intel vgpu export dma-buf failed\n");
> +		mutex_unlock(&dev->object_name_lock);
> +		return -EINVAL;
> +	}
> +
> +	ret = dma_buf_fd(dmabuf, exp_info.flags);
> +	if (ret < 0) {
> +		gvt_vgpu_err("intel vgpu create dma-buf fd failed\n");
> +		return ret;
> +	}
> +	info->fd = ret;
> +
> +	return 0;
> +}
> diff --git a/drivers/gpu/drm/i915/gvt/dmabuf.h b/drivers/gpu/drm/i915/gvt/dmabuf.h
> new file mode 100644
> index 0000000..c590f4a
> --- /dev/null
> +++ b/drivers/gpu/drm/i915/gvt/dmabuf.h
> @@ -0,0 +1,50 @@
> +/*
> + * Copyright(c) 2017 Intel Corporation. All rights reserved.
> + *
> + * Permission is hereby granted, free of charge, to any person obtaining a
> + * copy of this software and associated documentation files (the "Software"),
> + * to deal in the Software without restriction, including without limitation
> + * the rights to use, copy, modify, merge, publish, distribute, sublicense,
> + * and/or sell copies of the Software, and to permit persons to whom the
> + * Software is furnished to do so, subject to the following conditions:
> + *
> + * The above copyright notice and this permission notice (including the next
> + * paragraph) shall be included in all copies or substantial portions of the
> + * Software.
> + *
> + * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
> + * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
> + * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
> + * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
> + * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
> + * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
> + * SOFTWARE.
> + *
> + */
> +
> +#ifndef _GVT_DMABUF_H_
> +#define _GVT_DMABUF_H_
> +
> +#define INTEL_VGPU_QUERY_DMABUF		0
> +#define INTEL_VGPU_GENERATE_DMABUF	1
> +
> +struct intel_vgpu_dmabuf {

This looks to be uapi. What's it doing here?
-Chris

-- 
Chris Wilson, Intel Open Source Technology Centre

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