[vfio-users] Is stolen memory wasted after IGD passed through into guest os?

[Acewind]

In my guest os win7, before install intel graphic driver, 'total graphic
memory available' is 960KB.
After install intel graphic driver, reboot to bluescreen.
Where is 960KB from? SeaBIOS log shows 128M correctly and no error found in
dmesg.

Alex Williamson <alex.williamson at redhat.com> 于2018年9月25日周二 上午9:57写道：

> On Tue, 25 Sep 2018 09:44:24 +0800
> Acewind <acewind at gmail.com> wrote:
>
> > In my host os, command of ' lspci -v -s 00:02.0' will show:
> > Memory at e8000000 (64-bit, prefetchable) [size=128M]
> >
> > Is this 128M memory called 'stolen memory'?
>
> No, stolen memory is system memory dedicated to graphics use, it is not
> represented by a PCI BAR.
>
> > If this IGD device is passed through into guest os, will it be deserted
> and
> > wasted? Or mapped into and resused in guest os?
>
> PCI BARs are mapped to the VM.  SeaBIOS will attempt to allocate new
> stolen memory in the VM, so the host stolen memory is wasted, but it's
> not represented in a BAR.  Re-using the host stolen memory is difficult
> because it's not actually a resource associated with the device except
> through IGD usage and it's physical address space is immovable,
> creating holes in the VM address space at host specific addresses.
> Thanks,
>
> Alex
>
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