linux-kernel - Re: [PATCH v9 5/7] vfio: Define vfio based dma-buf operations

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Date:   Wed, 12 Jul 2017 18:48:47 +0530
From:   Kirti Wankhede <kwankhede@...dia.com>
To:     Gerd Hoffmann <kraxel@...hat.com>,
        Alex Williamson <alex.williamson@...hat.com>
CC:     Xiaoguang Chen <xiaoguang.chen@...el.com>,
        <chris@...is-wilson.co.uk>, <intel-gfx@...ts.freedesktop.org>,
        <linux-kernel@...r.kernel.org>, <zhenyuw@...ux.intel.com>,
        <zhiyuan.lv@...el.com>, <intel-gvt-dev@...ts.freedesktop.org>,
        <zhi.a.wang@...el.com>, <kevin.tian@...el.com>
Subject: Re: [PATCH v9 5/7] vfio: Define vfio based dma-buf operations

Hey Gerd,

Sorry, I missed this mail earlier.

On 6/21/2017 12:52 PM, Gerd Hoffmann wrote:
>   Hi,
> 
>> We don't support cursor for console vnc. Ideally console vnc should
>> be
>> used by admin for configuration or during maintenance, which refresh
>> primary surface at low refresh rate, 10 fps.
> 
> But you surely want a mouse pointer for the admin?
> You render it directly to the primary surface then I guess?
> 

If cursor surface is not provided, a dot for cursor is seen on the
primary surface, which is pretty much usable.

>> Right we need to know this at device initialization time for both
>> cases
>> to initialize VGACommonState structure for that device
> 
> Why do you need a VGACommonState?
> 

We need to create a GRAPHIC_CONSOLE for vGPU device and specify
GraphicHwOps so that from its .gfx_update callback, surface can be
queried and updated.

>> and also need
>> NONE to decide whether to init console vnc or not. We have a
>> mechanism
>> to disable console vnc path and we recommend to disable it for better
>> performance.
> 
> Hmm, maybe we should have a ioctl to configure the refresh rate, or a
> ioctl to allow qemu ask for a refresh when needed?
> 

What is default refresh rate of QEMU if vnc is connected?

Thanks,
Kirti

> qemu can throttle the display update rate, which for example happens in
> case no vnc client is connected.  qemu updates the display only once
> every few seconds then.
> 
> cheers,
>   Gerd
>