linux-kernel - [PATCH] drm/virtio: Remove restriction of non-zero blob

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Date:   Sat, 19 Feb 2022 09:03:01 -0800
From:   Rob Clark <robdclark@...il.com>
To:     dri-devel@...ts.freedesktop.org
Cc:     Chia-I Wu <olvaffe@...il.com>, Rob Clark <robdclark@...omium.org>,
        David Airlie <airlied@...ux.ie>,
        Gerd Hoffmann <kraxel@...hat.com>,
        Gurchetan Singh <gurchetansingh@...omium.org>,
        Daniel Vetter <daniel@...ll.ch>,
        virtualization@...ts.linux-foundation.org (open list:VIRTIO GPU DRIVER),
        linux-kernel@...r.kernel.org (open list)
Subject: [PATCH] drm/virtio: Remove restriction of non-zero blob_flags

From: Rob Clark <robdclark@...omium.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@...omium.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