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Thu, 8 May 2025 09:30:39 +0000 (UTC) Received: from dovecot-director2.suse.de ([2a07:de40:b281:106:10:150:64:167]) by imap1.dmz-prg2.suse.org with ESMTPSA id nOs2Nr95HGgscQAAD6G6ig (envelope-from ); Thu, 08 May 2025 09:30:39 +0000 Message-ID: <9eb1bdbb-6a0c-4771-ae61-4ba9bd7fbd14@suse.de> Date: Thu, 8 May 2025 11:30:39 +0200 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v3 1/3] drm/shmem-helper: Import dmabuf without mapping its sg_table To: oushixiong1025@163.com, =?UTF-8?Q?Christian_K=C3=B6nig?= Cc: Maarten Lankhorst , Maxime Ripard , David Airlie , Simona Vetter , Sean Paul , Jocelyn Falempe , dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org, Shixiong Ou References: <20250507094728.603302-1-oushixiong1025@163.com> Content-Language: en-US From: Thomas Zimmermann Autocrypt: addr=tzimmermann@suse.de; keydata= xsBNBFs50uABCADEHPidWt974CaxBVbrIBwqcq/WURinJ3+2WlIrKWspiP83vfZKaXhFYsdg XH47fDVbPPj+d6tQrw5lPQCyqjwrCPYnq3WlIBnGPJ4/jreTL6V+qfKRDlGLWFjZcsrPJGE0 BeB5BbqP5erN1qylK9i3gPoQjXGhpBpQYwRrEyQyjuvk+Ev0K1Jc5tVDeJAuau3TGNgah4Yc hdHm3bkPjz9EErV85RwvImQ1dptvx6s7xzwXTgGAsaYZsL8WCwDaTuqFa1d1jjlaxg6+tZsB 9GluwvIhSezPgnEmimZDkGnZRRSFiGP8yjqTjjWuf0bSj5rUnTGiyLyRZRNGcXmu6hjlABEB AAHNJ1Rob21hcyBaaW1tZXJtYW5uIDx0emltbWVybWFubkBzdXNlLmRlPsLAjgQTAQgAOAIb AwULCQgHAgYVCgkICwIEFgIDAQIeAQIXgBYhBHIX+6yM6c9jRKFo5WgNwR1TC3ojBQJftODH AAoJEGgNwR1TC3ojx1wH/0hKGWugiqDgLNXLRD/4TfHBEKmxIrmfu9Z5t7vwUKfwhFL6hqvo lXPJJKQpQ2z8+X2vZm/slsLn7J1yjrOsoJhKABDi+3QWWSGkaGwRJAdPVVyJMfJRNNNIKwVb U6B1BkX2XDKDGffF4TxlOpSQzdtNI/9gleOoUA8+jy8knnDYzjBNOZqLG2FuTdicBXblz0Mf vg41gd9kCwYXDnD91rJU8tzylXv03E75NCaTxTM+FBXPmsAVYQ4GYhhgFt8S2UWMoaaABLDe 7l5FdnLdDEcbmd8uLU2CaG4W2cLrUaI4jz2XbkcPQkqTQ3EB67hYkjiEE6Zy3ggOitiQGcqp j//OwE0EWznS4AEIAMYmP4M/V+T5RY5at/g7rUdNsLhWv1APYrh9RQefODYHrNRHUE9eosYb T6XMryR9hT8XlGOYRwKWwiQBoWSDiTMo/Xi29jUnn4BXfI2px2DTXwc22LKtLAgTRjP+qbU6 3Y0xnQN29UGDbYgyyK51DW3H0If2a3JNsheAAK+Xc9baj0LGIc8T9uiEWHBnCH+RdhgATnWW GKdDegUR5BkDfDg5O/FISymJBHx2Dyoklv5g4BzkgqTqwmaYzsl8UxZKvbaxq0zbehDda8lv hFXodNFMAgTLJlLuDYOGLK2AwbrS3Sp0AEbkpdJBb44qVlGm5bApZouHeJ/+n+7r12+lqdsA EQEAAcLAdgQYAQgAIAIbDBYhBHIX+6yM6c9jRKFo5WgNwR1TC3ojBQJftOH6AAoJEGgNwR1T C3ojVSkIALpAPkIJPQoURPb1VWjh34l0HlglmYHvZszJWTXYwavHR8+k6Baa6H7ufXNQtThR yIxJrQLW6rV5lm7TjhffEhxVCn37+cg0zZ3j7zIsSS0rx/aMwi6VhFJA5hfn3T0TtrijKP4A SAQO9xD1Zk9/61JWk8OysuIh7MXkl0fxbRKWE93XeQBhIJHQfnc+YBLprdnxR446Sh8Wn/2D Ya8cavuWf2zrB6cZurs048xe0UbSW5AOSo4V9M0jzYI4nZqTmPxYyXbm30Kvmz0rYVRaitYJ 4kyYYMhuULvrJDMjZRvaNe52tkKAvMevcGdt38H4KSVXAylqyQOW5zvPc4/sq9c= In-Reply-To: <20250507094728.603302-1-oushixiong1025@163.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-Spam-Flag: NO X-Spam-Score: -4.30 X-Spam-Level: X-Spamd-Result: default: False [-4.30 / 50.00]; BAYES_HAM(-3.00)[100.00%]; NEURAL_HAM_LONG(-1.00)[-1.000]; NEURAL_HAM_SHORT(-0.20)[-1.000]; MIME_GOOD(-0.10)[text/plain]; RCVD_TLS_ALL(0.00)[]; FREEMAIL_TO(0.00)[163.com,amd.com]; FREEMAIL_ENVRCPT(0.00)[163.com,gmail.com]; RCVD_VIA_SMTP_AUTH(0.00)[]; ARC_NA(0.00)[]; TO_DN_SOME(0.00)[]; MIME_TRACE(0.00)[0:+]; RCPT_COUNT_SEVEN(0.00)[11]; MID_RHS_MATCH_FROM(0.00)[]; FUZZY_BLOCKED(0.00)[rspamd.com]; FROM_HAS_DN(0.00)[]; FREEMAIL_CC(0.00)[linux.intel.com,kernel.org,gmail.com,ffwll.ch,poorly.run,redhat.com,lists.freedesktop.org,vger.kernel.org,kylinos.cn]; DKIM_SIGNED(0.00)[suse.de:s=susede2_rsa,suse.de:s=susede2_ed25519]; FROM_EQ_ENVFROM(0.00)[]; TO_MATCH_ENVRCPT_ALL(0.00)[]; RCVD_COUNT_TWO(0.00)[2]; DBL_BLOCKED_OPENRESOLVER(0.00)[kylinos.cn:email,suse.de:mid,imap1.dmz-prg2.suse.org:helo] Hi Am 07.05.25 um 11:47 schrieb oushixiong1025@163.com: > From: Shixiong Ou > > [WHY] > 1. Drivers using DRM_GEM_SHADOW_PLANE_HELPER_FUNCS and > DRM_GEM_SHMEM_DRIVER_OPS (e.g., udl, ast) do not require > sg_table import. > They only need dma_buf_vmap() to access the shared buffer's > kernel virtual address. > > 2. On certain Aspeed-based boards, a dma_mask of 0xffff_ffff may > trigger SWIOTLB during dmabuf import. However, IO_TLB_SEGSIZE > restricts the maximum DMA streaming mapping memory, resulting in > errors like: > > ast 0000:07:00.0: swiotlb buffer is full (sz: 3145728 bytes), total 32768 (slots), used 0 (slots) > > [HOW] > Provide a gem_prime_import implementation without sg_table mapping > to avoid issues (e.g., "swiotlb buffer is full"). Drivers that do not > require sg_table can adopt this. > > Signed-off-by: Shixiong Ou > --- > v1->v2: > Patch rebase. > v2->v3: > Rename the import callback function. > Remove drm_gem_shmem_prime_export() and separate some codes > to drm_gem_prime_import_self(). > > drivers/gpu/drm/drm_gem_shmem_helper.c | 51 ++++++++++++++++++++++++++ > drivers/gpu/drm/drm_prime.c | 46 +++++++++++++++++------ > include/drm/drm_gem_shmem_helper.h | 15 ++++++++ > include/drm/drm_prime.h | 3 ++ > 4 files changed, 104 insertions(+), 11 deletions(-) > > diff --git a/drivers/gpu/drm/drm_gem_shmem_helper.c b/drivers/gpu/drm/drm_gem_shmem_helper.c > index aa43265f4f4f..85900ec1954a 100644 > --- a/drivers/gpu/drm/drm_gem_shmem_helper.c > +++ b/drivers/gpu/drm/drm_gem_shmem_helper.c > @@ -800,6 +800,57 @@ drm_gem_shmem_prime_import_sg_table(struct drm_device *dev, > } > EXPORT_SYMBOL_GPL(drm_gem_shmem_prime_import_sg_table); > > +/** > + * drm_gem_shmem_prime_import_no_sgt - Import dmabuf without mapping its sg_table > + * @dev: Device to import into > + * @dma_buf: dma-buf object to import > + * > + * Drivers that use the shmem helpers but also wants to import dmabuf without > + * mapping its sg_table can use this as their &drm_driver.gem_prime_import > + * implementation. > + */ > +struct drm_gem_object *drm_gem_shmem_prime_import_no_sgt(struct drm_device *dev, > + struct dma_buf *dma_buf) > +{ > + struct dma_buf_attachment *attach; > + struct drm_gem_shmem_object *shmem; > + struct drm_gem_object *obj; > + size_t size; > + int ret; > + > + obj = drm_gem_prime_import_self(dev, dma_buf); > + if (obj) > + return obj; > + > + attach = dma_buf_attach(dma_buf, dev->dev); > + if (IS_ERR(attach)) > + return ERR_CAST(attach); > + > + get_dma_buf(dma_buf); > + > + size = PAGE_ALIGN(attach->dmabuf->size); > + > + shmem = __drm_gem_shmem_create(dev, size, true, NULL); > + if (IS_ERR(shmem)) { > + ret = PTR_ERR(shmem); > + goto fail_detach; > + } > + > + drm_dbg_prime(dev, "size = %zu\n", size); > + > + shmem->base.import_attach = attach; > + shmem->base.resv = dma_buf->resv; > + > + return &shmem->base; > + > +fail_detach: > + dma_buf_detach(dma_buf, attach); > + dma_buf_put(dma_buf); > + > + return ERR_PTR(ret); > +} > +EXPORT_SYMBOL_GPL(drm_gem_shmem_prime_import_no_sgt); > + > MODULE_DESCRIPTION("DRM SHMEM memory-management helpers"); > MODULE_IMPORT_NS("DMA_BUF"); > MODULE_LICENSE("GPL v2"); > diff --git a/drivers/gpu/drm/drm_prime.c b/drivers/gpu/drm/drm_prime.c > index d828502268b8..1e43b6022329 100644 > --- a/drivers/gpu/drm/drm_prime.c > +++ b/drivers/gpu/drm/drm_prime.c > @@ -910,6 +910,38 @@ struct dma_buf *drm_gem_prime_export(struct drm_gem_object *obj, > } > EXPORT_SYMBOL(drm_gem_prime_export); > > + > +/** > + * drm_gem_prime_import_self - Import a DMA-BUF exported from the same DRM device. > + * @dev: drm_device to check against > + * @dma_buf: dma-buf object to import > + * > + * This function checks if the DMA-BUF was exported from a GEM object belonging > + * to @dev. If so, it increments the GEM object's refcount and returns it directly. > + * > + * Return: GEM object if it belongs to @dev, NULL otherwise. > + */ > +struct drm_gem_object *drm_gem_prime_import_self(struct drm_device *dev, > + struct dma_buf *dma_buf) > +{ > + struct drm_gem_object *obj; > + > + if (dma_buf->ops == &drm_gem_prime_dmabuf_ops) { > + obj = dma_buf->priv; > + if (obj->dev == dev) { > + /* > + * Importing dmabuf exported from our own gem increases > + * refcount on gem itself instead of f_count of dmabuf. > + */ > + drm_gem_object_get(obj); > + return obj; > + } > + } > + > + return NULL; > +} > +EXPORT_SYMBOL(drm_gem_prime_import_self); > + I feel this helper is doing too much. Rather separate the test from the policy. Do something like bool drm_gem_prime_exported_dma_buf(dev, dma_buf) {     obj = dma_buf->priv;     return (dma_buf->ops == drm_gem_prime_dmabuf_ops) && (obj->dev == dev) } and in the callers do   if (drm_gem_prime_exported_dma_buf(dev, dma_buf)) {    /* ... */     obj = dma_buf->obj;     get(obj);     return obj;   } > /** > * drm_gem_prime_import_dev - core implementation of the import callback > * @dev: drm_device to import into > @@ -933,17 +965,9 @@ struct drm_gem_object *drm_gem_prime_import_dev(struct drm_device *dev, > struct drm_gem_object *obj; > int ret; > > - if (dma_buf->ops == &drm_gem_prime_dmabuf_ops) { > - obj = dma_buf->priv; > - if (obj->dev == dev) { > - /* > - * Importing dmabuf exported from our own gem increases > - * refcount on gem itself instead of f_count of dmabuf. > - */ > - drm_gem_object_get(obj); > - return obj; > - } > - } > + obj = drm_gem_prime_import_self(dev, dma_buf); > + if (obj) > + return obj; > > if (!dev->driver->gem_prime_import_sg_table) > return ERR_PTR(-EINVAL); > diff --git a/include/drm/drm_gem_shmem_helper.h b/include/drm/drm_gem_shmem_helper.h > index b4f993da3cae..6e8e907bc43e 100644 > --- a/include/drm/drm_gem_shmem_helper.h > +++ b/include/drm/drm_gem_shmem_helper.h > @@ -287,6 +287,8 @@ drm_gem_shmem_prime_import_sg_table(struct drm_device *dev, > struct sg_table *sgt); > int drm_gem_shmem_dumb_create(struct drm_file *file, struct drm_device *dev, > struct drm_mode_create_dumb *args); > +struct drm_gem_object *drm_gem_shmem_prime_import_no_sgt(struct drm_device *dev, > + struct dma_buf *buf); > > /** > * DRM_GEM_SHMEM_DRIVER_OPS - Default shmem GEM operations > @@ -298,4 +300,17 @@ int drm_gem_shmem_dumb_create(struct drm_file *file, struct drm_device *dev, > .gem_prime_import_sg_table = drm_gem_shmem_prime_import_sg_table, \ > .dumb_create = drm_gem_shmem_dumb_create > > +/** > + * DRM_GEM_SHMEM_DRIVER_OPS_FOR_VMAP - shmem GEM operations > + * without mapping sg_table on > + * imported buffer. > + * > + * This macro provides a shortcut for setting the shmem GEM operations in > + * the &drm_driver structure for drivers that do not require a sg_table on > + * imported buffers. Only vmap is supported on imported buffer. That final sentence is misleading. It would still be possible to pin/unpin and mmap the buffer. Only direct access from DMA-capable hardware is not. (Right?) > + */ > +#define DRM_GEM_SHMEM_DRIVER_OPS_FOR_VMAP \ Rather call this DRM_GEM_SHMEM_DRIVER_OPS_NO_SGT please. Calling it _FOR_VMAP seems misleading to me. Best regards Thomas > + .gem_prime_import = drm_gem_shmem_prime_import_no_sgt, \ > + .dumb_create = drm_gem_shmem_dumb_create > + > #endif /* __DRM_GEM_SHMEM_HELPER_H__ */ > diff --git a/include/drm/drm_prime.h b/include/drm/drm_prime.h > index fa085c44d4ca..b5179a9cde93 100644 > --- a/include/drm/drm_prime.h > +++ b/include/drm/drm_prime.h > @@ -100,6 +100,9 @@ struct dma_buf *drm_gem_prime_export(struct drm_gem_object *obj, > unsigned long drm_prime_get_contiguous_size(struct sg_table *sgt); > > /* helper functions for importing */ > +struct drm_gem_object *drm_gem_prime_import_self(struct drm_device *dev, > + struct dma_buf *dma_buf); > + > struct drm_gem_object *drm_gem_prime_import_dev(struct drm_device *dev, > struct dma_buf *dma_buf, > struct device *attach_dev); -- -- Thomas Zimmermann Graphics Driver Developer SUSE Software Solutions Germany GmbH Frankenstrasse 146, 90461 Nuernberg, Germany GF: Ivo Totev, Andrew Myers, Andrew McDonald, Boudien Moerman HRB 36809 (AG Nuernberg)