[vfio-users] [OVMF+VIFO+QEMU] Large VM RAM allocation = Long Boot Times

[Laszlo Ersek]

On 11/15/18 06:59, A Z wrote:
>  This is an issue that involves a combination of different software
> packages, so my apologies in advance if this is the wrong list to post on.
> 
> I'm experiencing terrible boot times when I assign a large amount of RAM to
> a VM when used in combination with VIFO/PCI-passthrough.
> 
> On a VM with a Nvidia GTX 970 + USB controller and 24GiB of RAM assigned,
> the time to the TianoCore splash screen is ~5 minutes. It's then ~30
> seconds before Windows 10 begins to boot (spinning dots). During this time,
> the QEMU CPU core threads are 100% busy.
> 
> According to `perf`, the QMU CPU core threads are spending most of their
> time waiting on a spinlock over kvm->mmu_lock that's created by
> kvm_zap_gfn_range.
> 
> I'm fairly certain that ~1 year ago (if not longer) the same configuration
> didn't take this long to boot.

If nothing at all had changed in your configuration, then the behavior
wouldn't have changed either. You must certainly have upgraded some
components since then, between host kernel, QEMU, and OVMF (likely all
of them). Please state the version numbers that work and don't work, and
try to isolate the issue to a version change that affects a *single*
component.

I vaguely recall similar reports from the past. I've been under the
impression that this kind of issue has been fixed. Thus, I'd guess you
are running old(er) versions of the affected component (whichever it
is), or else you are running bleeding edge, and the bug has crept back
in (new regression).

Thanks,
Laszlo