Re: [PATCH v2] drm/vmwgfx: Work around VMW_ALLOC_DMABUF

[Zack Rusin <zackr@vmware.com>]

On Fri, 2023-02-24 at 11:29 +0800, Meng Tang wrote:
> 
> 
> On 2023/2/24 11:13, Zack Rusin wrote:
> > 
> > That's correct. That's the way this works. The ioctl is allocating a buffer,
> > there's
> > no infinite space for buffers on a system and, given that your app just
> > allocates
> > and never frees buffers, at some point the space will run out and the ioctl will
> > return a failure.
> > 
> Do you mean that users without certain privileges can access allocate a 
> buffer because it is designed like this? so we don't need to block 
> users without certain privileges to VMW_ALLOC_DMABUF success?

That's correct. If only the drm master or admins could use rendering none of the
regular accelerated (e.g. OpenGL) apps would work.

> > As to the stack trace, I'm not sure what kernel you were testing it on so I
> > don't
> > have access to the full log but I can't reproduce it and there was a change
> > fixing
> > exactly this (i.e. buffer failed allocation but we were still accessing it) that
> > was
> > fixed in in 6.2 in commit 1a6897921f52 ("drm/vmwgfx: Stop accessing buffer
> > objects
> > which failed init") the change was backported as well, so you should be able to
> > verify on any kernel with it.
> > 
> > z
> > 
> Thank you, the kernel version of my environment is lower than 6.2, I 
> will verify on my kernel with commit 1a6897921f52 ("drm/vmwgfx: Stop 
> accessing buffer objects which failed init").

Great. Let me know if you have any problems with it.

z