linux-kernel - [PATCH] drm/virtio: Allow importing prime buffers when 3D is enabled

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [thread-next>] [day] [month] [year] [list]

Message-ID: <20251210154755.1119861-2-val@invisiblethingslab.com>
Date: Wed, 10 Dec 2025 12:39:23 -0300
From: Val Packett <val@...isiblethingslab.com>
To: David Airlie <airlied@...hat.com>,
	Gerd Hoffmann <kraxel@...hat.com>,
	Dmitry Osipenko <dmitry.osipenko@...labora.com>,
	Gurchetan Singh <gurchetansingh@...omium.org>,
	Chia-I Wu <olvaffe@...il.com>,
	Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
	Maxime Ripard <mripard@...nel.org>,
	Thomas Zimmermann <tzimmermann@...e.de>,
	Simona Vetter <simona@...ll.ch>,
	Vivek Kasireddy <vivek.kasireddy@...el.com>
Cc: Val Packett <val@...isiblethingslab.com>,
	Dongwon Kim <dongwon.kim@...el.com>,
	Christian Koenig <christian.koenig@....com>,
	dri-devel@...ts.freedesktop.org,
	virtualization@...ts.linux.dev,
	linux-kernel@...r.kernel.org
Subject: [PATCH] drm/virtio: Allow importing prime buffers when 3D is enabled

This functionality was added for using a KMS-only virtgpu with a physical
(or SR-IOV) headless GPU in passthrough, but it should not be restricted
to KMS-only mode. It can be used with cross-domain to pass guest memfds
to the host compositor with zero copies (using udmabuf on both sides).

Drop the check for the absence of virgl_3d to allow for more use cases.

Fixes: ca77f27a2665 ("drm/virtio: Import prime buffers from other devices as guest blobs")
Signed-off-by: Val Packett <val@...isiblethingslab.com>
---

Hi. I couldn't find any comments on that line in the reviews (on patchwork), so I assume
there was never a specific technical reason for that check, just an abundance of caution?

BTW, while here.. The drm_gem_prime_import "fallback" seems pretty much equivalent to
`return (-ENODEV)`, as drm_gem_prime_import(_dev) just translates the call to
gem_prime_import_sg_table which we don't use. Should it be replaced with `return (-ENODEV)`?

---
 drivers/gpu/drm/virtio/virtgpu_prime.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/virtio/virtgpu_prime.c b/drivers/gpu/drm/virtio/virtgpu_prime.c
index ce49282198cb..2fedd5d3bd62 100644
--- a/drivers/gpu/drm/virtio/virtgpu_prime.c
+++ b/drivers/gpu/drm/virtio/virtgpu_prime.c
@@ -312,7 +312,7 @@ struct drm_gem_object *virtgpu_gem_prime_import(struct drm_device *dev,
 		}
 	}

-	if (!vgdev->has_resource_blob || vgdev->has_virgl_3d)
+	if (!vgdev->has_resource_blob)
 		return drm_gem_prime_import(dev, buf);

 	bo = kzalloc(sizeof(*bo), GFP_KERNEL);
-- 
2.51.2