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Fri, 9 May 2025 06:51:57 +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 2h8NFw2mHWhTPAAAD6G6ig (envelope-from ); Fri, 09 May 2025 06:51:57 +0000 Message-ID: Date: Fri, 9 May 2025 08:51:57 +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 v4 1/3] drm/shmem-helper: Import dmabuf without mapping its sg_table To: =?UTF-8?Q?Christian_K=C3=B6nig?= , oushixiong1025@163.com 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: <20250509032040.185730-1-oushixiong1025@163.com> <301f1962-88a5-4ea1-bfc1-826426d01ab5@amd.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: <301f1962-88a5-4ea1-bfc1-826426d01ab5@amd.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)[amd.com,163.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)[suse.de:mid] Hi Am 09.05.25 um 08:22 schrieb Christian König: > On 5/9/25 05:20, oushixiong1025@163.com wrote: >> 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(). >> v3->v4: >> Separate the test from the policy. >> Rename the macro. >> >> drivers/gpu/drm/drm_gem_shmem_helper.c | 57 ++++++++++++++++++++++++++ >> drivers/gpu/drm/drm_prime.c | 36 ++++++++++++---- >> include/drm/drm_gem_shmem_helper.h | 15 +++++++ >> include/drm/drm_prime.h | 3 ++ >> 4 files changed, 102 insertions(+), 9 deletions(-) >> >> diff --git a/drivers/gpu/drm/drm_gem_shmem_helper.c b/drivers/gpu/drm/drm_gem_shmem_helper.c >> index aa43265f4f4f..8fa160c3635e 100644 >> --- a/drivers/gpu/drm/drm_gem_shmem_helper.c >> +++ b/drivers/gpu/drm/drm_gem_shmem_helper.c >> @@ -800,6 +800,63 @@ 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) > > Please don't mention "no sgt" in the name, that we use sgtable is an implementation detail. > > Maybe use something like "no map" or similar. To be fair, I asked to not named it something like _vmap(), but rather _no_sgt().  These vmap-only names purely describe a use case. I'd be OK with any name that refers to the difference between the various functions; not just their effect. > > >> +{ >> + struct dma_buf_attachment *attach; >> + struct drm_gem_shmem_object *shmem; >> + struct drm_gem_object *obj; >> + size_t size; >> + int ret; >> + >> + if (drm_gem_prime_exported_dma_buf(dev, dma_buf)) { >> + /* >> + * Importing dmabuf exported from our own gem increases >> + * refcount on gem itself instead of f_count of dmabuf. >> + */ >> + obj = dma_buf->priv; >> + drm_gem_object_get(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; >> + } Unrelated to this series, we might reconsider drm_driver.gem_prime_import_sg_table. If we move the call to dma_buf_map_attachment_unlocked() into the callback and rename it to gem_prime_import_attachment, using sg tables would become optional for all drivers. SHMEM would be able to create the object without SG table without having to reimplement the prime boiler-plate code. Thoughts? >> + >> + 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..5bcf483520b8 100644 >> --- a/drivers/gpu/drm/drm_prime.c >> +++ b/drivers/gpu/drm/drm_prime.c >> @@ -910,6 +910,26 @@ struct dma_buf *drm_gem_prime_export(struct drm_gem_object *obj, >> } >> EXPORT_SYMBOL(drm_gem_prime_export); >> >> + >> +/** >> + * drm_gem_prime_exported_dma_buf - >> + * checks if the DMA-BUF was exported from a GEM object belonging to @dev. >> + * @dev: drm_device to check against >> + * @dma_buf: dma-buf object to import >> + * >> + * Return: true if the DMA-BUF was exported from a GEM object belonging >> + * to @dev, false otherwise. >> + */ >> + >> +bool drm_gem_prime_exported_dma_buf(struct drm_device *dev, >> + struct dma_buf *dma_buf) > If I remember the naming conventions correctly this should be something like drm_gem_is_prime_exported_dma_buf(). Again my fault. But the name you suggested sounds correct. Best regards Thomas > > Regards, > Christian. > >> +{ >> + struct drm_gem_object *obj = dma_buf->priv; >> + >> + return (dma_buf->ops == &drm_gem_prime_dmabuf_ops) && (obj->dev == dev); >> +} >> +EXPORT_SYMBOL(drm_gem_prime_exported_dma_buf); >> + >> /** >> * drm_gem_prime_import_dev - core implementation of the import callback >> * @dev: drm_device to import into >> @@ -933,16 +953,14 @@ 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) { >> + if (drm_gem_prime_exported_dma_buf(dev, dma_buf)) { >> + /* >> + * Importing dmabuf exported from our own gem increases >> + * refcount on gem itself instead of f_count of dmabuf. >> + */ >> 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; >> - } >> + drm_gem_object_get(obj); >> + return obj; >> } >> >> if (!dev->driver->gem_prime_import_sg_table) >> diff --git a/include/drm/drm_gem_shmem_helper.h b/include/drm/drm_gem_shmem_helper.h >> index b4f993da3cae..9ee697ff52ea 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_NO_SGT - 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. >> + */ >> +#define DRM_GEM_SHMEM_DRIVER_OPS_NO_SGT \ >> + .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..ec83f1c077a4 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 */ >> +bool drm_gem_prime_exported_dma_buf(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)