Re: [PATCH] drm/xen-front: Remove CMA support

Oleksandr Andrushchenko
2018-04-17T09:08:35Z

On 04/17/2018 12:04 PM, Daniel Vetter wrote:
> On Tue, Apr 17, 2018 at 10:40:12AM +0300, Oleksandr Andrushchenko wrote:
>> From: Oleksandr Andrushchenko <oleksandr_andrushchenko@epam.com>
>>
>> Even if xen-front allocates its buffers from contiguous memory
>> those are still not contiguous in PA space, e.g. the buffer is only
>> contiguous in IPA space.
>> The only use-case for this mode was if xen-front is used to allocate
>> dumb buffers which later be used by some other driver requiring
>> contiguous memory, but there is no currently such a use-case or
>> it can be worked around with xen-front.
> Please also mention the nents confusion here, and the patch that fixes it.
> Or just outright take the commit message from my patch with all the
> details:
ok, if you don't mind then I'll use your commit message entirely
> drm/xen: Dissable CMA support
>
> It turns out this was only needed to paper over a bug in the CMA
> helpers, which was addressed in
>
> commit 998fb1a0f478b83492220ff79583bf9ad538bdd8
> 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.
>
> With the commit message improved:
>
> Acked-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Thank you,
I'll wait for a day and apply to drm-misc-next if this is ok
>
>> Signed-off-by: Oleksandr Andrushchenko <oleksandr_andrushchenko@epam.com>
>> Suggested-by: Daniel Vetter <daniel.vetter@ffwll.ch>
>> ---
>> Documentation/gpu/xen-front.rst | 12 ----
>> drivers/gpu/drm/xen/Kconfig | 13 ----
>> drivers/gpu/drm/xen/Makefile | 9 +--
>> drivers/gpu/drm/xen/xen_drm_front.c | 62 +++-------------
>> drivers/gpu/drm/xen/xen_drm_front.h | 42 ++---------
>> drivers/gpu/drm/xen/xen_drm_front_gem.c | 12 +---
>> drivers/gpu/drm/xen/xen_drm_front_gem.h | 3 -
>> drivers/gpu/drm/xen/xen_drm_front_gem_cma.c | 79 ---------------------
>> drivers/gpu/drm/xen/xen_drm_front_shbuf.c | 22 ------
>> drivers/gpu/drm/xen/xen_drm_front_shbuf.h | 8 ---
>> 10 files changed, 21 insertions(+), 241 deletions(-)
>> delete mode 100644 drivers/gpu/drm/xen/xen_drm_front_gem_cma.c
>>
>> diff --git a/Documentation/gpu/xen-front.rst b/Documentation/gpu/xen-front.rst
>> index 009d942386c5..d988da7d1983 100644
>> --- a/Documentation/gpu/xen-front.rst
>> +++ b/Documentation/gpu/xen-front.rst
>> @@ -18,18 +18,6 @@ Buffers allocated by the frontend driver
>> .. kernel-doc:: drivers/gpu/drm/xen/xen_drm_front.h
>> :doc: Buffers allocated by the frontend driver
>>
>> -With GEM CMA helpers
>> -~~~~~~~~~~~~~~~~~~~~
>> -
>> -.. kernel-doc:: drivers/gpu/drm/xen/xen_drm_front.h
>> - :doc: With GEM CMA helpers
>> -
>> -Without GEM CMA helpers
>> -~~~~~~~~~~~~~~~~~~~~~~~
>> -
>> -.. kernel-doc:: drivers/gpu/drm/xen/xen_drm_front.h
>> - :doc: Without GEM CMA helpers
>> -
>> Buffers allocated by the backend
>> --------------------------------
>>
>> diff --git a/drivers/gpu/drm/xen/Kconfig b/drivers/gpu/drm/xen/Kconfig
>> index 4f4abc91f3b6..4cca160782ab 100644
>> --- a/drivers/gpu/drm/xen/Kconfig
>> +++ b/drivers/gpu/drm/xen/Kconfig
>> @@ -15,16 +15,3 @@ config DRM_XEN_FRONTEND
>> help
>> Choose this option if you want to enable a para-virtualized
>> frontend DRM/KMS driver for Xen guest OSes.
>> -
>> -config DRM_XEN_FRONTEND_CMA
>> - bool "Use DRM CMA to allocate dumb buffers"
>> - depends on DRM_XEN_FRONTEND
>> - select DRM_KMS_CMA_HELPER
>> - select DRM_GEM_CMA_HELPER
>> - help
>> - Use DRM CMA helpers to allocate display buffers.
>> - This is useful for the use-cases when guest driver needs to
>> - share or export buffers to other drivers which only expect
>> - contiguous buffers.
>> - Note: in this mode driver cannot use buffers allocated
>> - by the backend.
>> diff --git a/drivers/gpu/drm/xen/Makefile b/drivers/gpu/drm/xen/Makefile
>> index 352730dc6c13..712afff5ffc3 100644
>> --- a/drivers/gpu/drm/xen/Makefile
>> +++ b/drivers/gpu/drm/xen/Makefile
>> @@ -5,12 +5,7 @@ drm_xen_front-objs := xen_drm_front.o \
>> xen_drm_front_conn.o \
>> xen_drm_front_evtchnl.o \
>> xen_drm_front_shbuf.o \
>> - xen_drm_front_cfg.o
>> -
>> -ifeq ($(CONFIG_DRM_XEN_FRONTEND_CMA),y)
>> - drm_xen_front-objs += xen_drm_front_gem_cma.o
>> -else
>> - drm_xen_front-objs += xen_drm_front_gem.o
>> -endif
>> + xen_drm_front_cfg.o \
>> + xen_drm_front_gem.o
>>
>> obj-$(CONFIG_DRM_XEN_FRONTEND) += drm_xen_front.o
>> diff --git a/drivers/gpu/drm/xen/xen_drm_front.c b/drivers/gpu/drm/xen/xen_drm_front.c
>> index 4a08b77f1c9e..1b0ea9ac330e 100644
>> --- a/drivers/gpu/drm/xen/xen_drm_front.c
>> +++ b/drivers/gpu/drm/xen/xen_drm_front.c
>> @@ -12,7 +12,6 @@
>> #include <drm/drm_atomic_helper.h>
>> #include <drm/drm_crtc_helper.h>
>> #include <drm/drm_gem.h>
>> -#include <drm/drm_gem_cma_helper.h>
>>
>> #include <linux/of_device.h>
>>
>> @@ -167,10 +166,9 @@ int xen_drm_front_mode_set(struct xen_drm_front_drm_pipeline *pipeline,
>> return ret;
>> }
>>
>> -static int be_dbuf_create_int(struct xen_drm_front_info *front_info,
>> +int xen_drm_front_dbuf_create(struct xen_drm_front_info *front_info,
>> u64 dbuf_cookie, u32 width, u32 height,
>> - u32 bpp, u64 size, struct page **pages,
>> - struct sg_table *sgt)
>> + u32 bpp, u64 size, struct page **pages)
>> {
>> struct xen_drm_front_evtchnl *evtchnl;
>> struct xen_drm_front_shbuf *shbuf;
>> @@ -187,7 +185,6 @@ static int be_dbuf_create_int(struct xen_drm_front_info *front_info,
>> buf_cfg.xb_dev = front_info->xb_dev;
>> buf_cfg.pages = pages;
>> buf_cfg.size = size;
>> - buf_cfg.sgt = sgt;
>> buf_cfg.be_alloc = front_info->cfg.be_alloc;
>>
>> shbuf = xen_drm_front_shbuf_alloc(&buf_cfg);
>> @@ -237,22 +234,6 @@ static int be_dbuf_create_int(struct xen_drm_front_info *front_info,
>> return ret;
>> }
>>
>> -int xen_drm_front_dbuf_create_from_sgt(struct xen_drm_front_info *front_info,
>> - u64 dbuf_cookie, u32 width, u32 height,
>> - u32 bpp, u64 size, struct sg_table *sgt)
>> -{
>> - return be_dbuf_create_int(front_info, dbuf_cookie, width, height,
>> - bpp, size, NULL, sgt);
>> -}
>> -
>> -int xen_drm_front_dbuf_create_from_pages(struct xen_drm_front_info *front_info,
>> - u64 dbuf_cookie, u32 width, u32 height,
>> - u32 bpp, u64 size, struct page **pages)
>> -{
>> - return be_dbuf_create_int(front_info, dbuf_cookie, width, height,
>> - bpp, size, pages, NULL);
>> -}
>> -
>> static int xen_drm_front_dbuf_destroy(struct xen_drm_front_info *front_info,
>> u64 dbuf_cookie)
>> {
>> @@ -434,24 +415,11 @@ static int xen_drm_drv_dumb_create(struct drm_file *filp,
>> goto fail;
>> }
>>
>> - /*
>> - * In case of CONFIG_DRM_XEN_FRONTEND_CMA gem_obj is constructed
>> - * via DRM CMA helpers and doesn't have ->pages allocated
>> - * (xendrm_gem_get_pages will return NULL), but instead can provide
>> - * sg table
>> - */
>> - if (xen_drm_front_gem_get_pages(obj))
>> - ret = xen_drm_front_dbuf_create_from_pages(drm_info->front_info,
>> - xen_drm_front_dbuf_to_cookie(obj),
>> - args->width, args->height, args->bpp,
>> - args->size,
>> - xen_drm_front_gem_get_pages(obj));
>> - else
>> - ret = xen_drm_front_dbuf_create_from_sgt(drm_info->front_info,
>> - xen_drm_front_dbuf_to_cookie(obj),
>> - args->width, args->height, args->bpp,
>> - args->size,
>> - xen_drm_front_gem_get_sg_table(obj));
>> + ret = xen_drm_front_dbuf_create(drm_info->front_info,
>> + xen_drm_front_dbuf_to_cookie(obj),
>> + args->width, args->height, args->bpp,
>> + args->size,
>> + xen_drm_front_gem_get_pages(obj));
>> if (ret)
>> goto fail_backend;
>>
>> @@ -523,11 +491,7 @@ static const struct file_operations xen_drm_dev_fops = {
>> .poll = drm_poll,
>> .read = drm_read,
>> .llseek = no_llseek,
>> -#ifdef CONFIG_DRM_XEN_FRONTEND_CMA
>> - .mmap = drm_gem_cma_mmap,
>> -#else
>> .mmap = xen_drm_front_gem_mmap,
>> -#endif
>> };
>>
>> static const struct vm_operations_struct xen_drm_drv_vm_ops = {
>> @@ -547,6 +511,9 @@ static struct drm_driver xen_drm_driver = {
>> .gem_prime_export = drm_gem_prime_export,
>> .gem_prime_import_sg_table = xen_drm_front_gem_import_sg_table,
>> .gem_prime_get_sg_table = xen_drm_front_gem_get_sg_table,
>> + .gem_prime_vmap = xen_drm_front_gem_prime_vmap,
>> + .gem_prime_vunmap = xen_drm_front_gem_prime_vunmap,
>> + .gem_prime_mmap = xen_drm_front_gem_prime_mmap,
>> .dumb_create = xen_drm_drv_dumb_create,
>> .fops = &xen_drm_dev_fops,
>> .name = "xendrm-du",
>> @@ -555,15 +522,6 @@ static struct drm_driver xen_drm_driver = {
>> .major = 1,
>> .minor = 0,
>>
>> -#ifdef CONFIG_DRM_XEN_FRONTEND_CMA
>> - .gem_prime_vmap = drm_gem_cma_prime_vmap,
>> - .gem_prime_vunmap = drm_gem_cma_prime_vunmap,
>> - .gem_prime_mmap = drm_gem_cma_prime_mmap,
>> -#else
>> - .gem_prime_vmap = xen_drm_front_gem_prime_vmap,
>> - .gem_prime_vunmap = xen_drm_front_gem_prime_vunmap,
>> - .gem_prime_mmap = xen_drm_front_gem_prime_mmap,
>> -#endif
>> };
>>
>> static int xen_drm_drv_init(struct xen_drm_front_info *front_info)
>> diff --git a/drivers/gpu/drm/xen/xen_drm_front.h b/drivers/gpu/drm/xen/xen_drm_front.h
>> index 16554b2463d8..2c2479b571ae 100644
>> --- a/drivers/gpu/drm/xen/xen_drm_front.h
>> +++ b/drivers/gpu/drm/xen/xen_drm_front.h
>> @@ -23,40 +23,14 @@
>> *
>> * Depending on the requirements for the para-virtualized environment, namely
>> * requirements dictated by the accompanying DRM/(v)GPU drivers running in both
>> - * host and guest environments, number of operating modes of para-virtualized
>> - * display driver are supported:
>> - *
>> - * - display buffers can be allocated by either frontend driver or backend
>> - * - display buffers can be allocated to be contiguous in memory or not
>> - *
>> - * Note! Frontend driver itself has no dependency on contiguous memory for
>> - * its operation.
>> + * host and guest environments, display buffers can be allocated by either
>> + * frontend driver or backend.
>> */
>>
>> /**
>> * DOC: Buffers allocated by the frontend driver
>> *
>> - * The below modes of operation are configured at compile-time via
>> - * frontend driver's kernel configuration:
>> - */
>> -
>> -/**
>> - * DOC: With GEM CMA helpers
>> - *
>> - * This use-case is useful when used with accompanying DRM/vGPU driver in
>> - * guest domain which was designed to only work with contiguous buffers,
>> - * e.g. DRM driver based on GEM CMA helpers: such drivers can only import
>> - * contiguous PRIME buffers, thus requiring frontend driver to provide
>> - * such. In order to implement this mode of operation para-virtualized
>> - * frontend driver can be configured to use GEM CMA helpers.
>> - */
>> -
>> -/**
>> - * DOC: Without GEM CMA helpers
>> - *
>> - * If accompanying drivers can cope with non-contiguous memory then, to
>> - * lower pressure on CMA subsystem of the kernel, driver can allocate
>> - * buffers from system memory.
>> + * In this mode of operation driver allocates buffers from system memory.
>> *
>> * Note! If used with accompanying DRM/(v)GPU drivers this mode of operation
>> * may require IOMMU support on the platform, so accompanying DRM/vGPU
>> @@ -164,13 +138,9 @@ int xen_drm_front_mode_set(struct xen_drm_front_drm_pipeline *pipeline,
>> u32 x, u32 y, u32 width, u32 height,
>> u32 bpp, u64 fb_cookie);
>>
>> -int xen_drm_front_dbuf_create_from_sgt(struct xen_drm_front_info *front_info,
>> - u64 dbuf_cookie, u32 width, u32 height,
>> - u32 bpp, u64 size, struct sg_table *sgt);
>> -
>> -int xen_drm_front_dbuf_create_from_pages(struct xen_drm_front_info *front_info,
>> - u64 dbuf_cookie, u32 width, u32 height,
>> - u32 bpp, u64 size, struct page **pages);
>> +int xen_drm_front_dbuf_create(struct xen_drm_front_info *front_info,
>> + u64 dbuf_cookie, u32 width, u32 height,
>> + u32 bpp, u64 size, struct page **pages);
>>
>> int xen_drm_front_fb_attach(struct xen_drm_front_info *front_info,
>> u64 dbuf_cookie, u64 fb_cookie, u32 width,
>> diff --git a/drivers/gpu/drm/xen/xen_drm_front_gem.c b/drivers/gpu/drm/xen/xen_drm_front_gem.c
>> index 3b04a2269d7a..c85bfe7571cb 100644
>> --- a/drivers/gpu/drm/xen/xen_drm_front_gem.c
>> +++ b/drivers/gpu/drm/xen/xen_drm_front_gem.c
>> @@ -210,15 +210,9 @@ xen_drm_front_gem_import_sg_table(struct drm_device *dev,
>> if (ret < 0)
>> return ERR_PTR(ret);
>>
>> - /*
>> - * N.B. Although we have an API to create display buffer from sgt
>> - * we use pages API, because we still need those for GEM handling,
>> - * e.g. for mapping etc.
>> - */
>> - ret = xen_drm_front_dbuf_create_from_pages(drm_info->front_info,
>> - xen_drm_front_dbuf_to_cookie(&xen_obj->base),
>> - 0, 0, 0, size,
>> - xen_obj->pages);
>> + ret = xen_drm_front_dbuf_create(drm_info->front_info,
>> + xen_drm_front_dbuf_to_cookie(&xen_obj->base),
>> + 0, 0, 0, size, xen_obj->pages);
>> if (ret < 0)
>> return ERR_PTR(ret);
>>
>> diff --git a/drivers/gpu/drm/xen/xen_drm_front_gem.h b/drivers/gpu/drm/xen/xen_drm_front_gem.h
>> index 55e531f5a763..d5ab734fdafe 100644
>> --- a/drivers/gpu/drm/xen/xen_drm_front_gem.h
>> +++ b/drivers/gpu/drm/xen/xen_drm_front_gem.h
>> @@ -27,8 +27,6 @@ struct page **xen_drm_front_gem_get_pages(struct drm_gem_object *obj);
>>
>> void xen_drm_front_gem_free_object_unlocked(struct drm_gem_object *gem_obj);
>>
>> -#ifndef CONFIG_DRM_XEN_FRONTEND_CMA
>> -
>> int xen_drm_front_gem_mmap(struct file *filp, struct vm_area_struct *vma);
>>
>> void *xen_drm_front_gem_prime_vmap(struct drm_gem_object *gem_obj);
>> @@ -38,6 +36,5 @@ void xen_drm_front_gem_prime_vunmap(struct drm_gem_object *gem_obj,
>>
>> int xen_drm_front_gem_prime_mmap(struct drm_gem_object *gem_obj,
>> struct vm_area_struct *vma);
>> -#endif
>>
>> #endif /* __XEN_DRM_FRONT_GEM_H */
>> diff --git a/drivers/gpu/drm/xen/xen_drm_front_gem_cma.c b/drivers/gpu/drm/xen/xen_drm_front_gem_cma.c
>> deleted file mode 100644
>> index ba30a4bc2a39..000000000000
>> --- a/drivers/gpu/drm/xen/xen_drm_front_gem_cma.c
>> +++ /dev/null
>> @@ -1,79 +0,0 @@
>> -// SPDX-License-Identifier: GPL-2.0 OR MIT
>> -
>> -/*
>> - * Xen para-virtual DRM device
>> - *
>> - * Copyright (C) 2016-2018 EPAM Systems Inc.
>> - *
>> - * Author: Oleksandr Andrushchenko <oleksandr_andrushchenko@epam.com>
>> - */
>> -
>> -#include <drm/drmP.h>
>> -#include <drm/drm_gem.h>
>> -#include <drm/drm_fb_cma_helper.h>
>> -#include <drm/drm_gem_cma_helper.h>
>> -
>> -#include "xen_drm_front.h"
>> -#include "xen_drm_front_gem.h"
>> -
>> -struct drm_gem_object *
>> -xen_drm_front_gem_import_sg_table(struct drm_device *dev,
>> - struct dma_buf_attachment *attach,
>> - struct sg_table *sgt)
>> -{
>> - struct xen_drm_front_drm_info *drm_info = dev->dev_private;
>> - struct drm_gem_object *gem_obj;
>> - struct drm_gem_cma_object *cma_obj;
>> - int ret;
>> -
>> - gem_obj = drm_gem_cma_prime_import_sg_table(dev, attach, sgt);
>> - if (IS_ERR_OR_NULL(gem_obj))
>> - return gem_obj;
>> -
>> - cma_obj = to_drm_gem_cma_obj(gem_obj);
>> -
>> - ret = xen_drm_front_dbuf_create_from_sgt(drm_info->front_info,
>> - xen_drm_front_dbuf_to_cookie(gem_obj),
>> - 0, 0, 0, gem_obj->size,
>> - drm_gem_cma_prime_get_sg_table(gem_obj));
>> - if (ret < 0)
>> - return ERR_PTR(ret);
>> -
>> - DRM_DEBUG("Imported CMA buffer of size %zu\n", gem_obj->size);
>> -
>> - return gem_obj;
>> -}
>> -
>> -struct sg_table *xen_drm_front_gem_get_sg_table(struct drm_gem_object *gem_obj)
>> -{
>> - return drm_gem_cma_prime_get_sg_table(gem_obj);
>> -}
>> -
>> -struct drm_gem_object *xen_drm_front_gem_create(struct drm_device *dev,
>> - size_t size)
>> -{
>> - struct xen_drm_front_drm_info *drm_info = dev->dev_private;
>> - struct drm_gem_cma_object *cma_obj;
>> -
>> - if (drm_info->front_info->cfg.be_alloc) {
>> - /* This use-case is not yet supported and probably won't be */
>> - DRM_ERROR("Backend allocated buffers and CMA helpers are not supported at the same time\n");
>> - return ERR_PTR(-EINVAL);
>> - }
>> -
>> - cma_obj = drm_gem_cma_create(dev, size);
>> - if (IS_ERR_OR_NULL(cma_obj))
>> - return ERR_CAST(cma_obj);
>> -
>> - return &cma_obj->base;
>> -}
>> -
>> -void xen_drm_front_gem_free_object_unlocked(struct drm_gem_object *gem_obj)
>> -{
>> - drm_gem_cma_free_object(gem_obj);
>> -}
>> -
>> -struct page **xen_drm_front_gem_get_pages(struct drm_gem_object *gem_obj)
>> -{
>> - return NULL;
>> -}
>> diff --git a/drivers/gpu/drm/xen/xen_drm_front_shbuf.c b/drivers/gpu/drm/xen/xen_drm_front_shbuf.c
>> index 19914dde4b3d..d5705251a0d6 100644
>> --- a/drivers/gpu/drm/xen/xen_drm_front_shbuf.c
>> +++ b/drivers/gpu/drm/xen/xen_drm_front_shbuf.c
>> @@ -89,10 +89,6 @@ void xen_drm_front_shbuf_free(struct xen_drm_front_shbuf *buf)
>> }
>> kfree(buf->grefs);
>> kfree(buf->directory);
>> - if (buf->sgt) {
>> - sg_free_table(buf->sgt);
>> - kvfree(buf->pages);
>> - }
>> kfree(buf);
>> }
>>
>> @@ -350,17 +346,6 @@ static int grant_references(struct xen_drm_front_shbuf *buf)
>>
>> static int alloc_storage(struct xen_drm_front_shbuf *buf)
>> {
>> - if (buf->sgt) {
>> - buf->pages = kvmalloc_array(buf->num_pages,
>> - sizeof(struct page *), GFP_KERNEL);
>> - if (!buf->pages)
>> - return -ENOMEM;
>> -
>> - if (drm_prime_sg_to_page_addr_arrays(buf->sgt, buf->pages,
>> - NULL, buf->num_pages) < 0)
>> - return -EINVAL;
>> - }
>> -
>> buf->grefs = kcalloc(buf->num_grefs, sizeof(*buf->grefs), GFP_KERNEL);
>> if (!buf->grefs)
>> return -ENOMEM;
>> @@ -396,12 +381,6 @@ xen_drm_front_shbuf_alloc(struct xen_drm_front_shbuf_cfg *cfg)
>> struct xen_drm_front_shbuf *buf;
>> int ret;
>>
>> - /* either pages or sgt, not both */
>> - if (unlikely(cfg->pages && cfg->sgt)) {
>> - DRM_ERROR("Cannot handle buffer allocation with both pages and sg table provided\n");
>> - return NULL;
>> - }
>> -
>> buf = kzalloc(sizeof(*buf), GFP_KERNEL);
>> if (!buf)
>> return NULL;
>> @@ -413,7 +392,6 @@ xen_drm_front_shbuf_alloc(struct xen_drm_front_shbuf_cfg *cfg)
>>
>> buf->xb_dev = cfg->xb_dev;
>> buf->num_pages = DIV_ROUND_UP(cfg->size, PAGE_SIZE);
>> - buf->sgt = cfg->sgt;
>> buf->pages = cfg->pages;
>>
>> buf->ops->calc_num_grefs(buf);
>> diff --git a/drivers/gpu/drm/xen/xen_drm_front_shbuf.h b/drivers/gpu/drm/xen/xen_drm_front_shbuf.h
>> index 8c037fd7608b..7545c692539e 100644
>> --- a/drivers/gpu/drm/xen/xen_drm_front_shbuf.h
>> +++ b/drivers/gpu/drm/xen/xen_drm_front_shbuf.h
>> @@ -29,16 +29,9 @@ struct xen_drm_front_shbuf {
>> grant_ref_t *grefs;
>> unsigned char *directory;
>>
>> - /*
>> - * there are 2 ways to provide backing storage for this shared buffer:
>> - * either pages or sgt. if buffer created from sgt then we own
>> - * the pages and must free those ourselves on closure
>> - */
>> int num_pages;
>> struct page **pages;
>>
>> - struct sg_table *sgt;
>> -
>> struct xenbus_device *xb_dev;
>>
>> /* these are the ops used internally depending on be_alloc mode */
>> @@ -52,7 +45,6 @@ struct xen_drm_front_shbuf_cfg {
>> struct xenbus_device *xb_dev;
>> size_t size;
>> struct page **pages;
>> - struct sg_table *sgt;
>> bool be_alloc;
>> };
>>
>> --
>> 2.17.0
>>
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