Re: [Qemu-discuss] Booting GUI ubuntu VM on Aarch64

[Yehuda Yitschak]

Hi Alexander

> From: Alexander Spyridakis [mailto:address@hidden 
> Sent: Monday, February 15, 2016 15:38
> To: Yehuda Yitschak
> Cc: Peter Maydell; address@hidden; address@hidden; Jérémy Fanguède
> Subject: Re: [Qemu-discuss] Booting GUI ubuntu VM on Aarch64
>
> Hello,
>
> On 15 February 2016 at 12:55, Yehuda Yitschak <address@hidden> wrote:
> I just built qemu-2.5 so I can try the virtio-gpu-pci approach.
>
> Btw - I found a demo from virtual open system where they show guest graphics 
> on Exynos based Arndale board.
> It doesn’t show how but maybe it gives a hint
> http://www.virtualopensystems.com/en/solutions/demos/kvm-on-arndale-exynos/
>
>
>
> Are you interested in graphics with TCG or KVM? With TCG the usual command 
> line should work out of the box with the default bochs vga device: "-device 
> VGA -device usb-ehci -device usb-tablet - device usb-kbd". Don't forget to 
> enable the bochs driver in your guest kernel, and depending on your distro 
> you might have to play around with the X configuration to get it right.
>
> With KVM as Peter mentioned, you need some additional patches for device 
> cache coherency. Have a look at two patches from Jeremy Fanguede: "[RFC 0/4] 
> arm/arm64: KVM: Get around cache incoherency" and "[RFC] ARM/ARM64: KVM: 
> Implement KVM_FLUSH_DCACHE_GPA ioctl". These patches are not meant only for 
> the VGA, but also emulated usb devices, without them your mouse and >  
> keyboard won't work.

I want to use KVM tough it looks like a not a trivial hack for the non QEMU 
expert like me :) 
Would  you mind sharing how you achieved graphics in your demo above ?
did you use TCG or did you also go through these workarounds ? 

Thanks a lot 

Yehuda 

> Additionally, with KVM you might need to brute-force the rendering of the VGA 
> device in QEMU by removing the check on memory_region_get_dirty(). This is a 
> very ugly hack but it should work (hw/display/vga.c in vga_draw_graphic), 
> which is similar to this: 
> https://github.com/virtualopensystems/qemu/commit/64dd1b3e3a2353433edb9c63d00271f515bd06fb
Regards.