Re: [Xen-devel] [Xen-users] Dom0 freeze on HVM DomU Windows reboot with VGA passthrough

["Dr. Greg Wettstein" <greg@xxxxxxxxxxxxxxxxx>]

On Mar 17,  6:14pm, Howell Tam wrote:
} Subject: Re: [Xen-users] Dom0 freeze on HVM DomU Windows reboot with VGA p

> Hi all again,

Hi, hope the weekend is going well for everyone.

> > > have you found a solution for this behaviour? Cause I'm currently
> > > seeing a similar result with my installation.
> 
>       I've been away for a few weeks and I'm finally back on trying to figure
> out this problem.
> 
>       I was using xl + xl pci-assignable-add when I get the full
> machine freeze when I reboot the domU windows7.
> 
>       I just tried with the same domu config file, but with xm +
> pci-stub, and I do not seem to get the freeze (yet, so far 3 
> reboots/shutdowns).
> 
>       The VGA passthrough (an HD7770) is still working even after the
> reboot (i.e. no more blank screen).
> 
>       This is semi-good news. If the bug is in xl, then I guess we
> will have to debug this since xm is deprecated.

I believe its reasonable to say we have worked with VGA pass-through
as much as anyone at this point, given we try to maintain the
'unofficial' VGA pass-through patch for QEMU.  So the community can
take the following as a datapoint.

All of our research and development work is based on 4.2.x and as of
4.2.1 using xl for VGA pass-through is a complete non-starter.  This
is primary pass-through using Radeon with our patch as we do not use
the secondary model.  The target VM is Windows 7.

The primary behavior we see is that the VM will boot to the login
screen.  After logging in the VM crashes and it isn't very subtle.
Re-starting the VM requires Windows to go through a full crash
recovery sequence.

In a small number of cases dom0 gets completely taken out leaving the
sound card buzzing..... :-)

Other priorities have kept us from going hunting for this but it is on
our agenda.  We just found a bug in blktap2 teardown which we have
been hunting since 4.2.x came out so hopefully we will find some
cycles for it.

> Regards,

Have a good week.

Greg

}-- End of excerpt from Howell Tam

As always,
Dr. G.W. Wettstein, Ph.D.   Enjellic Systems Development, LLC.
4206 N. 19th Ave.           Specializing in information infra-structure
Fargo, ND  58102            development.
PH: 701-281-1686
FAX: 701-281-3949           EMAIL: greg@xxxxxxxxxxxx
------------------------------------------------------------------------------
"The price of reliability is the pursuit of the utmost simplicity."
                                -- C.A.R. Hoare
                                   1980 ACM Turning Award Lecture

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