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smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com; spf=pass smtp.mailfrom=arm.com; arc=none smtp.client-ip=217.140.110.172 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=arm.com Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id CBD21152B; Wed, 16 Apr 2025 02:22:47 -0700 (PDT) Received: from [10.57.90.52] (unknown [10.57.90.52]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 9682A3F66E; Wed, 16 Apr 2025 02:22:45 -0700 (PDT) Message-ID: <43260764-4940-4faa-ac07-7138f306a062@arm.com> Date: Wed, 16 Apr 2025 10:22:43 +0100 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 v7 2/4] drm/panthor: Add driver IOCTL for setting BO labels To: =?UTF-8?Q?Adri=C3=A1n_Larumbe?= Cc: Boris Brezillon , Liviu Dudau , Maarten Lankhorst , Maxime Ripard , Thomas Zimmermann , David Airlie , Simona Vetter , Sumit Semwal , =?UTF-8?Q?Christian_K=C3=B6nig?= , kernel@collabora.com, dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org, linux-media@vger.kernel.org, linaro-mm-sig@lists.linaro.org References: <20250411150357.3308921-1-adrian.larumbe@collabora.com> <20250411150357.3308921-3-adrian.larumbe@collabora.com> <6d67aff0-7082-4966-acb2-d7985820b3ea@arm.com> From: Steven Price Content-Language: en-GB In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit On 14/04/2025 21:41, Adrián Larumbe wrote: > On 14.04.2025 11:01, Steven Price wrote: >> On 11/04/2025 16:03, Adrián Larumbe wrote: >>> Allow UM to label a BO for which it possesses a DRM handle. >>> >>> Signed-off-by: Adrián Larumbe >>> Reviewed-by: Liviu Dudau >>> Reviewed-by: Boris Brezillon >> >> Reviewed-by: Steven Price >> >> Although very minor NITs below which you can consider. >> >>> --- >>> drivers/gpu/drm/panthor/panthor_drv.c | 42 ++++++++++++++++++++++++++- >>> drivers/gpu/drm/panthor/panthor_gem.h | 2 ++ >>> include/uapi/drm/panthor_drm.h | 23 +++++++++++++++ >>> 3 files changed, 66 insertions(+), 1 deletion(-) >>> >>> diff --git a/drivers/gpu/drm/panthor/panthor_drv.c b/drivers/gpu/drm/panthor/panthor_drv.c >>> index 06fe46e32073..983b24f1236c 100644 >>> --- a/drivers/gpu/drm/panthor/panthor_drv.c >>> +++ b/drivers/gpu/drm/panthor/panthor_drv.c >>> @@ -1331,6 +1331,44 @@ static int panthor_ioctl_vm_get_state(struct drm_device *ddev, void *data, >>> return 0; >>> } >>> >>> +static int panthor_ioctl_bo_set_label(struct drm_device *ddev, void *data, >>> + struct drm_file *file) >>> +{ >>> + struct drm_panthor_bo_set_label *args = data; >>> + struct drm_gem_object *obj; >>> + const char *label; >>> + int ret = 0; >>> + >>> + obj = drm_gem_object_lookup(file, args->handle); >>> + if (!obj) >>> + return -ENOENT; >>> + >>> + if (args->size && args->label) { >>> + if (args->size > PANTHOR_BO_LABEL_MAXLEN) { >>> + ret = -E2BIG; >>> + goto err_label; >>> + } >>> + >>> + label = strndup_user(u64_to_user_ptr(args->label), args->size); >>> + if (IS_ERR(label)) { >>> + ret = PTR_ERR(label); >>> + goto err_label; >>> + } >>> + } else if (args->size && !args->label) { >>> + ret = -EINVAL; >>> + goto err_label; >>> + } else { >>> + label = NULL; >>> + } >>> + >>> + panthor_gem_bo_set_label(obj, label); >>> + >>> +err_label: >>> + drm_gem_object_put(obj); >>> + >>> + return ret; >>> +} >>> + >>> static int >>> panthor_open(struct drm_device *ddev, struct drm_file *file) >>> { >>> @@ -1400,6 +1438,7 @@ static const struct drm_ioctl_desc panthor_drm_driver_ioctls[] = { >>> PANTHOR_IOCTL(TILER_HEAP_CREATE, tiler_heap_create, DRM_RENDER_ALLOW), >>> PANTHOR_IOCTL(TILER_HEAP_DESTROY, tiler_heap_destroy, DRM_RENDER_ALLOW), >>> PANTHOR_IOCTL(GROUP_SUBMIT, group_submit, DRM_RENDER_ALLOW), >>> + PANTHOR_IOCTL(BO_SET_LABEL, bo_set_label, DRM_RENDER_ALLOW), >>> }; >>> >>> static int panthor_mmap(struct file *filp, struct vm_area_struct *vma) >>> @@ -1509,6 +1548,7 @@ static void panthor_debugfs_init(struct drm_minor *minor) >>> * - 1.2 - adds DEV_QUERY_GROUP_PRIORITIES_INFO query >>> * - adds PANTHOR_GROUP_PRIORITY_REALTIME priority >>> * - 1.3 - adds DRM_PANTHOR_GROUP_STATE_INNOCENT flag >>> + * - 1.4 - adds DRM_IOCTL_PANTHOR_BO_SET_LABEL ioctl >>> */ >>> static const struct drm_driver panthor_drm_driver = { >>> .driver_features = DRIVER_RENDER | DRIVER_GEM | DRIVER_SYNCOBJ | >>> @@ -1522,7 +1562,7 @@ static const struct drm_driver panthor_drm_driver = { >>> .name = "panthor", >>> .desc = "Panthor DRM driver", >>> .major = 1, >>> - .minor = 3, >>> + .minor = 4, >>> >>> .gem_create_object = panthor_gem_create_object, >>> .gem_prime_import_sg_table = drm_gem_shmem_prime_import_sg_table, >>> diff --git a/drivers/gpu/drm/panthor/panthor_gem.h b/drivers/gpu/drm/panthor/panthor_gem.h >>> index af0d77338860..beba066b4974 100644 >>> --- a/drivers/gpu/drm/panthor/panthor_gem.h >>> +++ b/drivers/gpu/drm/panthor/panthor_gem.h >>> @@ -13,6 +13,8 @@ >>> >>> struct panthor_vm; >>> >>> +#define PANTHOR_BO_LABEL_MAXLEN PAGE_SIZE >>> + >>> /** >>> * struct panthor_gem_object - Driver specific GEM object. >>> */ >>> diff --git a/include/uapi/drm/panthor_drm.h b/include/uapi/drm/panthor_drm.h >>> index 97e2c4510e69..12b1994499a9 100644 >>> --- a/include/uapi/drm/panthor_drm.h >>> +++ b/include/uapi/drm/panthor_drm.h >>> @@ -127,6 +127,9 @@ enum drm_panthor_ioctl_id { >>> >>> /** @DRM_PANTHOR_TILER_HEAP_DESTROY: Destroy a tiler heap. */ >>> DRM_PANTHOR_TILER_HEAP_DESTROY, >>> + >>> + /** @DRM_PANTHOR_BO_SET_LABEL: Label a BO. */ >>> + DRM_PANTHOR_BO_SET_LABEL, >>> }; >>> >>> /** >>> @@ -977,6 +980,24 @@ struct drm_panthor_tiler_heap_destroy { >>> __u32 pad; >>> }; >>> >>> +/** >>> + * struct drm_panthor_bo_set_label - Arguments passed to DRM_IOCTL_PANTHOR_BO_SET_LABEL >>> + */ >>> +struct drm_panthor_bo_set_label { >>> + /** @handle: Handle of the buffer object to label. */ >>> + __u32 handle; >>> + >>> + /** >>> + * @size: Length of the label, including the NULL terminator. >>> + * >>> + * Cannot be greater than the OS page size. >>> + */ >>> + __u32 size; >>> + >>> + /** @label: User pointer to a NULL-terminated string */ >>> + __u64 label; >>> +}; >> >> First very minor NIT: >> * NULL is a pointer, i.e. (void*)0 >> * NUL is the ASCII code point '\0'. >> So it's a NUL-terminated string. > > Fixed > >> Second NIT: We don't actually need 'size' - since the string is >> NUL-terminated we can just strndup_user(__user_pointer__, PAGE_SIZE). >> As things stand we validate that strlen(label) < size <= PAGE_SIZE - >> which is a little odd (user space might as well just pass PAGE_SIZE >> rather than calculate the actual length). > > The snag I see in this approach is that the only way to make sure > strlen(label) + 1 <= PAGE_SIZE would be doing something like > > label = strndup_user(u64_to_user_ptr(args->label), args->size); > if (strlen(label) + 1 <= PAGE_SIZE) { > kfree(label) > return -E2BIG; > } You can just do strndup_user(u64_to_user_ptr(args->label), PAGE_SIZE) If you look at the kernel's implementation it handles an overly long string by returning an error: > length = strnlen_user(s, n); > > if (!length) > return ERR_PTR(-EFAULT); > > if (length > n) > return ERR_PTR(-EINVAL); > > p = memdup_user(s, length); So there's no need to call strlen() on the result. > In the meantime, we've duplicated the string and traversed a whole page > of bytes, all to be discarded at once. > > In this case, I think it's alright to expect some cooperation from UM > in supplying the actual size, although I'm really not an expert in > designing elegant uAPIs, so if you think this looks very odd I'd be > glad to replace it with. > > Actually, as I was writing this, I realised that strndup_user() calls > strnlen_user(), which is publicly available for other drivers, so > I might check the length first, and if it falls within bounds, do > the actual user stringdup. Again, no need (and strnlen_user() has a comment basically saying "don't call this"). strndup_user() has all the magic we need here. As I say this is just a 'nit' - so no big deal. But I don't really see the point of the size in the uAPI. Take a look at dma_buf_set_name() for an example which sets the name on a dma_buf (and doesn't take a size argument) - although that wasn't an example of good uAPI design as the type in the ioctl was botched ;( Thanks, Steve > I shall also mention the size bound on the uAPI for the 'label' pointer. > >> Thanks, >> Steve >> >> + >> /** >> * DRM_IOCTL_PANTHOR() - Build a Panthor IOCTL number >> * @__access: Access type. Must be R, W or RW. >> @@ -1019,6 +1040,8 @@ enum { >> DRM_IOCTL_PANTHOR(WR, TILER_HEAP_CREATE, tiler_heap_create), >> DRM_IOCTL_PANTHOR_TILER_HEAP_DESTROY = >> DRM_IOCTL_PANTHOR(WR, TILER_HEAP_DESTROY, tiler_heap_destroy), >> + DRM_IOCTL_PANTHOR_BO_SET_LABEL = >> + DRM_IOCTL_PANTHOR(WR, BO_SET_LABEL, bo_set_label), >> }; >> >> #if defined(__cplusplus) > > > Adrian Larumbe