Re: [Qemu-devel] [Bug 1580459] Re: Windows (10?) guest freezes entire host on shutdown if using PCI passthrough

[Alex Williamson]

On Thu, 07 Jul 2016 20:34:15 -0000
Clif Houck <address@hidden> wrote:

> I was also experiencing the host hard locking when shutting down a
> Windows 10 guest with a Nvidia GPU passed-through, but the issue appears
> to be completely solved after switching the card to MSI mode in the
> Windows guest.
> 
> However, I would be interested in understanding *why* using the card in
> line-interrupt mode in the guest causes the host to lockup when the
> guest relinquishes control of the device. Is it a bug in qemu or vfio,
> or even the Linux kernel?
> 
> I don't know if its relevant, but I've noticed when the card is not
> being used by the guest it is listed as MSI: Enable- by lspci,
> suggesting that vfio is keeping the card in line-interrupt mode when not
> in use.
> 

Interrupts are disabled when the card is not in use.  Can you test
whether the following commit fixes the problem:

http://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=956b56a984ddf10aa69b25318dc04430101beed6

This was added in v4.7-rc2, so it will also be included in anything
newer.  Thanks,

Alex