Virtualization - Feb 2022 - [PATCH] drm/virtio: Remove restriction of non-zero blob_flags

From: Rob Clark <robdclark at chromium.org>

With native userspace drivers in guest, a lot of GEM objects need to be
neither shared nor mappable.  And in fact making everything mappable
and/or sharable results in unreasonably high fd usage in host VMM.

Signed-off-by: Rob Clark <robdclark at chromium.org>
---
This is for a thing I'm working on, a new virtgpu context type that
allows for running native userspace driver in the guest, with a
thin shim in the host VMM.  In this case, the guest has a lot of
GEM buffer objects which need to be neither shared nor mappable.

This supersedes https://patchwork.freedesktop.org/patch/475127/

 drivers/gpu/drm/virtio/virtgpu_ioctl.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/virtio/virtgpu_ioctl.c
b/drivers/gpu/drm/virtio/virtgpu_ioctl.c
index 69f1952f3144..3a8078f2ee27 100644
--- a/drivers/gpu/drm/virtio/virtgpu_ioctl.c
+++ b/drivers/gpu/drm/virtio/virtgpu_ioctl.c
@@ -617,8 +617,7 @@ static int verify_blob(struct virtio_gpu_device *vgdev,
 	if (!vgdev->has_resource_blob)
 		return -EINVAL;
 
-	if ((rc_blob->blob_flags & ~VIRTGPU_BLOB_FLAG_USE_MASK) ||
-	    !rc_blob->blob_flags)
+	if (rc_blob->blob_flags & ~VIRTGPU_BLOB_FLAG_USE_MASK)
 		return -EINVAL;
 
 	if (rc_blob->blob_flags & VIRTGPU_BLOB_FLAG_USE_CROSS_DEVICE) {
-- 
2.34.1

On Sat, Feb 19, 2022 at 9:02 AM Rob Clark <robdclark at gmail.com>
wrote:
>
> From: Rob Clark <robdclark at chromium.org>
>
> With native userspace drivers in guest, a lot of GEM objects need to be
> neither shared nor mappable.  And in fact making everything mappable
> and/or sharable results in unreasonably high fd usage in host VMM.
>
> Signed-off-by: Rob Clark <robdclark at chromium.org>
Reviewed-by: Chia-I Wu <olvaffe at gmail.com>