Re: [Xen-devel] [PATCH v2 25/24] xl: Document VGA problems arising from lack of physmap dmop

[Paul Durrant <Paul.Durrant@xxxxxxxxxx>]

> -----Original Message-----
> From: Ian Jackson [mailto:ian.jackson@xxxxxxxxxxxxx]
> Sent: 06 October 2017 16:02
> To: Paul Durrant <Paul.Durrant@xxxxxxxxxx>
> Cc: Wei Liu <wei.liu2@xxxxxxxxxx>; xen-devel@xxxxxxxxxxxxxxxxxxx; Ross
> Lagerwall <ross.lagerwall@xxxxxxxxxx>
> Subject: RE: [PATCH v2 25/24] xl: Document VGA problems arising from lack
> of physmap dmop
> 
> Paul Durrant writes ("RE: [PATCH v2 25/24] xl: Document VGA problems
> arising from lack of physmap dmop"):
> > I suspect what it happening is that the VRAM is not moved into the BAR,
> but the emulation in QEMU instead handles the BAR writes and then updates
> the VRAM in its current location.
> 
> Is it going to be a problem that the vram is still mapped in its
> previous location ?
> 

Unclear. I think it of those things where QEMU knows where it is but nothing 
else really does. With trad the VRAM was always just below the 4G boundary in 
guest space but this is not the case with upstream so I don't know what the 
risk of something else trying to put memory (or a hotplugged device) in the 
same space is.

  Paul

> Ian.

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