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Date:   Fri, 15 Jul 2022 09:31:12 +0200
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Subject: Re: [PATCH v1 2/6] drm/gem: Take reservation lock for vmap/vunmap
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To:     Dmitry Osipenko <dmitry.osipenko@collabora.com>,
        David Airlie <airlied@linux.ie>,
        Gerd Hoffmann <kraxel@redhat.com>,
        Gurchetan Singh <gurchetansingh@chromium.org>,
        Chia-I Wu <olvaffe@gmail.com>, Daniel Vetter <daniel@ffwll.ch>,
        Daniel Almeida <daniel.almeida@collabora.com>,
        Gert Wollny <gert.wollny@collabora.com>,
        Gustavo Padovan <gustavo.padovan@collabora.com>,
        Daniel Stone <daniel@fooishbar.org>,
        Tomeu Vizoso <tomeu.vizoso@collabora.com>,
        Maarten Lankhorst <maarten.lankhorst@linux.intel.com>,
        Maxime Ripard <mripard@kernel.org>,
        Thomas Zimmermann <tzimmermann@suse.de>,
        Rob Clark <robdclark@gmail.com>,
        Sumit Semwal <sumit.semwal@linaro.org>,
        "Pan, Xinhui" <Xinhui.Pan@amd.com>,
        Thierry Reding <thierry.reding@gmail.com>,
        Tomasz Figa <tfiga@chromium.org>,
        Marek Szyprowski <m.szyprowski@samsung.com>,
        Mauro Carvalho Chehab <mchehab@kernel.org>,
        Alex Deucher <alexander.deucher@amd.com>,
        Jani Nikula <jani.nikula@linux.intel.com>,
        Joonas Lahtinen <joonas.lahtinen@linux.intel.com>,
        Rodrigo Vivi <rodrigo.vivi@intel.com>,
        Tvrtko Ursulin <tvrtko.ursulin@linux.intel.com>,
        =?UTF-8?Q?Thomas_Hellstr=c3=b6m?= <thomas_os@shipmail.org>,
        Thomas Zimmermann <tzimmermann@suse.de>
Cc:     dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org,
        Dmitry Osipenko <digetx@gmail.com>,
        linux-media@vger.kernel.org, linaro-mm-sig@lists.linaro.org,
        amd-gfx@lists.freedesktop.org, intel-gfx@lists.freedesktop.org,
        kernel@collabora.com, virtualization@lists.linux-foundation.org,
        spice-devel@lists.freedesktop.org, linux-rdma@vger.kernel.org,
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References: <20220715005244.42198-1-dmitry.osipenko@collabora.com>
 <20220715005244.42198-3-dmitry.osipenko@collabora.com>
From:   =?UTF-8?Q?Christian_K=c3=b6nig?= <christian.koenig@amd.com>
In-Reply-To: <20220715005244.42198-3-dmitry.osipenko@collabora.com>
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Am 15.07.22 um 02:52 schrieb Dmitry Osipenko:
> The new common dma-buf locking convention will require buffer importers
> to hold the reservation lock around mapping operations. Make DRM GEM core
> to take the lock around the vmapping operations and update QXL and i915
> drivers to use the locked functions for the case where DRM core now holds
> the lock. This patch prepares DRM core and drivers to transition to the
> common dma-buf locking convention where vmapping of exported GEMs will
> be done under the held reservation lock.

Oh ^^ That looks like a bug fix to me!

At least drm_gem_ttm_vmap() and drm_gem_ttm_vunmap() already expected 
that they are called with the reservation lock held.

Otherwise you could mess up internal structures in the TTM buffer object 
while vmapping it.

I will take a deeper look at this.

Regards,
Christian.

>
> Signed-off-by: Dmitry Osipenko <dmitry.osipenko@collabora.com>
> ---
>   drivers/gpu/drm/drm_client.c                 |  4 +--
>   drivers/gpu/drm/drm_gem.c                    | 28 ++++++++++++++++++++
>   drivers/gpu/drm/drm_gem_framebuffer_helper.c |  6 ++---
>   drivers/gpu/drm/drm_prime.c                  |  4 +--
>   drivers/gpu/drm/i915/gem/i915_gem_dmabuf.c   |  2 +-
>   drivers/gpu/drm/qxl/qxl_object.c             | 17 ++++++------
>   drivers/gpu/drm/qxl/qxl_prime.c              |  4 +--
>   include/drm/drm_gem.h                        |  3 +++
>   8 files changed, 50 insertions(+), 18 deletions(-)
>
> diff --git a/drivers/gpu/drm/drm_client.c b/drivers/gpu/drm/drm_client.c
> index 2b230b4d6942..fbcb1e995384 100644
> --- a/drivers/gpu/drm/drm_client.c
> +++ b/drivers/gpu/drm/drm_client.c
> @@ -323,7 +323,7 @@ drm_client_buffer_vmap(struct drm_client_buffer *buffer,
>   	 * fd_install step out of the driver backend hooks, to make that
>   	 * final step optional for internal users.
>   	 */
> -	ret = drm_gem_vmap(buffer->gem, map);
> +	ret = drm_gem_vmap_unlocked(buffer->gem, map);
>   	if (ret)
>   		return ret;
>   
> @@ -345,7 +345,7 @@ void drm_client_buffer_vunmap(struct drm_client_buffer *buffer)
>   {
>   	struct iosys_map *map = &buffer->map;
>   
> -	drm_gem_vunmap(buffer->gem, map);
> +	drm_gem_vunmap_unlocked(buffer->gem, map);
>   }
>   EXPORT_SYMBOL(drm_client_buffer_vunmap);
>   
> diff --git a/drivers/gpu/drm/drm_gem.c b/drivers/gpu/drm/drm_gem.c
> index eb0c2d041f13..9769c33cad99 100644
> --- a/drivers/gpu/drm/drm_gem.c
> +++ b/drivers/gpu/drm/drm_gem.c
> @@ -1155,6 +1155,8 @@ void drm_gem_print_info(struct drm_printer *p, unsigned int indent,
>   
>   int drm_gem_pin(struct drm_gem_object *obj)
>   {
> +	dma_resv_assert_held(obj->resv);
> +
>   	if (obj->funcs->pin)
>   		return obj->funcs->pin(obj);
>   	else
> @@ -1163,6 +1165,8 @@ int drm_gem_pin(struct drm_gem_object *obj)
>   
>   void drm_gem_unpin(struct drm_gem_object *obj)
>   {
> +	dma_resv_assert_held(obj->resv);
> +
>   	if (obj->funcs->unpin)
>   		obj->funcs->unpin(obj);
>   }
> @@ -1171,6 +1175,8 @@ int drm_gem_vmap(struct drm_gem_object *obj, struct iosys_map *map)
>   {
>   	int ret;
>   
> +	dma_resv_assert_held(obj->resv);
> +
>   	if (!obj->funcs->vmap)
>   		return -EOPNOTSUPP;
>   
> @@ -1186,6 +1192,8 @@ EXPORT_SYMBOL(drm_gem_vmap);
>   
>   void drm_gem_vunmap(struct drm_gem_object *obj, struct iosys_map *map)
>   {
> +	dma_resv_assert_held(obj->resv);
> +
>   	if (iosys_map_is_null(map))
>   		return;
>   
> @@ -1197,6 +1205,26 @@ void drm_gem_vunmap(struct drm_gem_object *obj, struct iosys_map *map)
>   }
>   EXPORT_SYMBOL(drm_gem_vunmap);
>   
> +int drm_gem_vmap_unlocked(struct drm_gem_object *obj, struct iosys_map *map)
> +{
> +	int ret;
> +
> +	dma_resv_lock(obj->resv, NULL);
> +	ret = drm_gem_vmap(obj, map);
> +	dma_resv_unlock(obj->resv);
> +
> +	return ret;
> +}
> +EXPORT_SYMBOL(drm_gem_vmap_unlocked);
> +
> +void drm_gem_vunmap_unlocked(struct drm_gem_object *obj, struct iosys_map *map)
> +{
> +	dma_resv_lock(obj->resv, NULL);
> +	drm_gem_vunmap(obj, map);
> +	dma_resv_unlock(obj->resv);
> +}
> +EXPORT_SYMBOL(drm_gem_vunmap_unlocked);
> +
>   /**
>    * drm_gem_lock_reservations - Sets up the ww context and acquires
>    * the lock on an array of GEM objects.
> diff --git a/drivers/gpu/drm/drm_gem_framebuffer_helper.c b/drivers/gpu/drm/drm_gem_framebuffer_helper.c
> index 880a4975507f..e35e224e6303 100644
> --- a/drivers/gpu/drm/drm_gem_framebuffer_helper.c
> +++ b/drivers/gpu/drm/drm_gem_framebuffer_helper.c
> @@ -354,7 +354,7 @@ int drm_gem_fb_vmap(struct drm_framebuffer *fb, struct iosys_map *map,
>   			ret = -EINVAL;
>   			goto err_drm_gem_vunmap;
>   		}
> -		ret = drm_gem_vmap(obj, &map[i]);
> +		ret = drm_gem_vmap_unlocked(obj, &map[i]);
>   		if (ret)
>   			goto err_drm_gem_vunmap;
>   	}
> @@ -376,7 +376,7 @@ int drm_gem_fb_vmap(struct drm_framebuffer *fb, struct iosys_map *map,
>   		obj = drm_gem_fb_get_obj(fb, i);
>   		if (!obj)
>   			continue;
> -		drm_gem_vunmap(obj, &map[i]);
> +		drm_gem_vunmap_unlocked(obj, &map[i]);
>   	}
>   	return ret;
>   }
> @@ -403,7 +403,7 @@ void drm_gem_fb_vunmap(struct drm_framebuffer *fb, struct iosys_map *map)
>   			continue;
>   		if (iosys_map_is_null(&map[i]))
>   			continue;
> -		drm_gem_vunmap(obj, &map[i]);
> +		drm_gem_vunmap_unlocked(obj, &map[i]);
>   	}
>   }
>   EXPORT_SYMBOL(drm_gem_fb_vunmap);
> diff --git a/drivers/gpu/drm/drm_prime.c b/drivers/gpu/drm/drm_prime.c
> index b75ef1756873..1bd234fd21a5 100644
> --- a/drivers/gpu/drm/drm_prime.c
> +++ b/drivers/gpu/drm/drm_prime.c
> @@ -678,7 +678,7 @@ int drm_gem_dmabuf_vmap(struct dma_buf *dma_buf, struct iosys_map *map)
>   {
>   	struct drm_gem_object *obj = dma_buf->priv;
>   
> -	return drm_gem_vmap(obj, map);
> +	return drm_gem_vmap_unlocked(obj, map);
>   }
>   EXPORT_SYMBOL(drm_gem_dmabuf_vmap);
>   
> @@ -694,7 +694,7 @@ void drm_gem_dmabuf_vunmap(struct dma_buf *dma_buf, struct iosys_map *map)
>   {
>   	struct drm_gem_object *obj = dma_buf->priv;
>   
> -	drm_gem_vunmap(obj, map);
> +	drm_gem_vunmap_unlocked(obj, map);
>   }
>   EXPORT_SYMBOL(drm_gem_dmabuf_vunmap);
>   
> diff --git a/drivers/gpu/drm/i915/gem/i915_gem_dmabuf.c b/drivers/gpu/drm/i915/gem/i915_gem_dmabuf.c
> index 5ecea7df98b1..cc54a5b1d6ae 100644
> --- a/drivers/gpu/drm/i915/gem/i915_gem_dmabuf.c
> +++ b/drivers/gpu/drm/i915/gem/i915_gem_dmabuf.c
> @@ -72,7 +72,7 @@ static int i915_gem_dmabuf_vmap(struct dma_buf *dma_buf,
>   	struct drm_i915_gem_object *obj = dma_buf_to_obj(dma_buf);
>   	void *vaddr;
>   
> -	vaddr = i915_gem_object_pin_map_unlocked(obj, I915_MAP_WB);
> +	vaddr = i915_gem_object_pin_map(obj, I915_MAP_WB);
>   	if (IS_ERR(vaddr))
>   		return PTR_ERR(vaddr);
>   
> diff --git a/drivers/gpu/drm/qxl/qxl_object.c b/drivers/gpu/drm/qxl/qxl_object.c
> index 695d9308d1f0..06a58dad5f5c 100644
> --- a/drivers/gpu/drm/qxl/qxl_object.c
> +++ b/drivers/gpu/drm/qxl/qxl_object.c
> @@ -168,9 +168,16 @@ int qxl_bo_vmap_locked(struct qxl_bo *bo, struct iosys_map *map)
>   		bo->map_count++;
>   		goto out;
>   	}
> -	r = ttm_bo_vmap(&bo->tbo, &bo->map);
> +
> +	r = __qxl_bo_pin(bo);
>   	if (r)
>   		return r;
> +
> +	r = ttm_bo_vmap(&bo->tbo, &bo->map);
> +	if (r) {
> +		__qxl_bo_unpin(bo);
> +		return r;
> +	}
>   	bo->map_count = 1;
>   
>   	/* TODO: Remove kptr in favor of map everywhere. */
> @@ -192,12 +199,6 @@ int qxl_bo_vmap(struct qxl_bo *bo, struct iosys_map *map)
>   	if (r)
>   		return r;
>   
> -	r = __qxl_bo_pin(bo);
> -	if (r) {
> -		qxl_bo_unreserve(bo);
> -		return r;
> -	}
> -
>   	r = qxl_bo_vmap_locked(bo, map);
>   	qxl_bo_unreserve(bo);
>   	return r;
> @@ -247,6 +248,7 @@ void qxl_bo_vunmap_locked(struct qxl_bo *bo)
>   		return;
>   	bo->kptr = NULL;
>   	ttm_bo_vunmap(&bo->tbo, &bo->map);
> +	__qxl_bo_unpin(bo);
>   }
>   
>   int qxl_bo_vunmap(struct qxl_bo *bo)
> @@ -258,7 +260,6 @@ int qxl_bo_vunmap(struct qxl_bo *bo)
>   		return r;
>   
>   	qxl_bo_vunmap_locked(bo);
> -	__qxl_bo_unpin(bo);
>   	qxl_bo_unreserve(bo);
>   	return 0;
>   }
> diff --git a/drivers/gpu/drm/qxl/qxl_prime.c b/drivers/gpu/drm/qxl/qxl_prime.c
> index 142d01415acb..9169c26357d3 100644
> --- a/drivers/gpu/drm/qxl/qxl_prime.c
> +++ b/drivers/gpu/drm/qxl/qxl_prime.c
> @@ -59,7 +59,7 @@ int qxl_gem_prime_vmap(struct drm_gem_object *obj, struct iosys_map *map)
>   	struct qxl_bo *bo = gem_to_qxl_bo(obj);
>   	int ret;
>   
> -	ret = qxl_bo_vmap(bo, map);
> +	ret = qxl_bo_vmap_locked(bo, map);
>   	if (ret < 0)
>   		return ret;
>   
> @@ -71,5 +71,5 @@ void qxl_gem_prime_vunmap(struct drm_gem_object *obj,
>   {
>   	struct qxl_bo *bo = gem_to_qxl_bo(obj);
>   
> -	qxl_bo_vunmap(bo);
> +	qxl_bo_vunmap_locked(bo);
>   }
> diff --git a/include/drm/drm_gem.h b/include/drm/drm_gem.h
> index 87cffc9efa85..bf3700415229 100644
> --- a/include/drm/drm_gem.h
> +++ b/include/drm/drm_gem.h
> @@ -420,4 +420,7 @@ void drm_gem_unlock_reservations(struct drm_gem_object **objs, int count,
>   int drm_gem_dumb_map_offset(struct drm_file *file, struct drm_device *dev,
>   			    u32 handle, u64 *offset);
>   
> +int drm_gem_vmap_unlocked(struct drm_gem_object *obj, struct iosys_map *map);
> +void drm_gem_vunmap_unlocked(struct drm_gem_object *obj, struct iosys_map *map);
> +
>   #endif /* __DRM_GEM_H__ */