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An update about primary passthrough: I managed to get primary passthrough working with KVM and a AMD Radeon HD 7770 running Windows 7 Pro 64bit in the guest (with the AMD driver) and it does shorten the guest boot time. Other than that I can't say that KVM performs any better or worse than Xen, except that some benchmark applications such as Passmark PerformanceTest failed to run and caused a BSOD under KVM. Only in SAFEMODE was I able to run Passmark, but I haven't tried yet a solution that was offered to me.

While the benefits of primary passthrough for the user may be minor (shortened boot time), I do believe that this should be a development goal as the process becomes more predictable (the moment you boot the guest you see its output on the guest screen, exactly like booting on bare metal).

On Friday, May 2, 2014 10:08 AM, H. Sieger <powerhouse.linux@xxxxxxxxx> wrote:

Well, I've recently gave KVM a try and saw primary passthrough working in my setup - that was until I installed the AMD driver in Windows after which the guest didn't boot anymore/blue screen *:(
sad

.

I believe primary passthrough can shorten the boot time of the guest, but other than that I wouldn't break my head over that.

On Thursday, May 1, 2014 2:48 PM, Daniel E. Shub <daniel.shub@xxxxxxxxxxxxxxxx> wrote:

On Thursday 01 May 2014 11:50:34 Gordan Bobic wrote:
> On 2014-05-01 11:34, Daniel E. Shub wrote:
> > I posted this question over at
> > http://unix.stackexchange.com/questions/123510/differences-between-primary
> > -and-secondary-vga-pass-through-in-virtualization but didn't get an answer
> > so I
> > thought I would try here ...
> >
> > From the wiki I think I understand why passing a VGA adapter through is
> > more
> > difficult than passing a standard PCI device through and to some extent
> > why
> > passing a VGA adapter through as the primary device is more difficult
> > than
> > passing it through as a secondary device. What I m confused about is
> > what are
> > the advantages of passing a VGA adapter through as the primary device
> > as
> > opposed to the secondary device?
>
> The only advantage of passing the interface as primary (and FWIW I have
> never actually seen this work) is that in that case you get to see the
> SeaBIOS POST screen and the domU OS boot progress before it loads the
> GPU
> driver. Other than that, I am not aware of any advantage.
>
> Gordan
>
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> http://lists.xen.org/xen-users

If that is true, it seems like people are doing a lot of work for not too many
advantages. So much of the information on the web about VGA pass through is
confusing at best and often just wrong.

Dan
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Re: [Xen-users] Difference between primary and secondary VGA pass through