[PATCH v2 2/5] drm/virtio: Add a helper to map and note the dma addrs and lengths

[Kasireddy, Vivek]

Hi Dmitry,

> Subject: Re: [PATCH v2 2/5] drm/virtio: Add a helper to map and note the
> dma addrs and lengths
> >> ...
> >>> After rebasing v2 of this patch series on top of the above patch, I see that
> >>> this use-case works as expected with Qemu master. Let me send out v3,
> >>> which would be a rebase of v2 on top of the above patch.
> >> ...
> >>>>> Am I doing anything wrong? Suggestions are welcome.
> >>>> Could you please share your Qemu launch parameters? I'll try to
> recreate
> >> the
> >>>> issue you are seeing.
> >>
> >> Thanks a lot for sharing your Qemu command. I haven't used the
> >> `host-phys-bits` flags, will try again soon and then also check host
> >> errors if it still won't work.
> > Any chance you would be able to finish reviewing this patch series before
> > your upcoming vacation?
> 
> Let's try, we have a week.
Oh, it is going to be very tight, given that it is a short working week in the
U.S (Thanksgiving holidays start on Wed/Thu). But, yeah, let us try.

> 
> Good news, I got it to work with latest misc-next+v3 on guest and by
> using passthroughed AMD RDNA3 card instead of DG2. Haven't yet checked
> whether DG2 works with this guest kernel combination, maybe it will.
Yeah, DG2 should work as well with latest drm-tip and Qemu master.

> 
> A bit bad news is that display flickers on each framebuffer flip (shows
> a black screen) using dynamic dmabuf attachment. Pinning imported
> dma-buf permanently fixes the flicker, i.e. dynamic dmabuf attachment
> doesn't work as expected. Disabling CONFIG_DMABUF_MOVE_NOTIFY helps.
I'd like to get this case (dynamic dmabuf attachment) to work successfully as well.
If it is not too much trouble, could you please try to test with DG2 to see if this
flickering issue happens there as well? Since I have access to a DG2 card, I'd like
to recreate this flickering issue in my test environment and try to fix it.

> 
> There are these virtio-gpu errors on each flicker:
> 
> [drm:virtio_gpu_dequeue_ctrl_func] *ERROR* response 0x1200 (command
> 0x106)
> 
> Overall, patches are good to me. I'll leave couple comments on the v3.
> The flickering issue isn't a blocker given that MOVE_NOTIFY is
> considered to be experimental today, we can fix it later.
Ok, I'll try to address your comments and send out a v4 soon.

Thanks,
Vivek

> 
> --
> Best regards,
> Dmitry