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

[A Z]

 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.

Regards,
Adam
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