Re: [edk2-devel] [BUG] Extremely slow boot times with CPU and GPU passthrough and host phys-bits > 40

["mitchell.augustin via groups.io" <mitchell.augustin=canonical.com@groups.io>]

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Thanks for the suggestions, Gerd.

> '-global ICH9-LPC.acpi-pci-hotplug-with-bridge-support=off'

Unfortunatly, this did not result in any change in boot time.

> '-cpu $name,host-phys-bits=on,host-phys-bits-limit=$bits'

-cpu host,host-phys-bits=on,host-phys-bits-limit=40 does result in the desired very fast boot time, but I get errors when I try to load the GPU driver:

NVRM: BAR0 is 0M @ 0x0 (PCI:0000:06:00.0)

NVRM: This PCI I/O region assigned to your NVIDIA device is invalid:

**

*This is the same thing I see when trying to load the driver on OVMF versions without the DynamicMMIOWindowSize patch as well, but with those versions, I don't get the errors and everything works if I boot with `pci=realloc pci=nocrs`. That is not the case here, when I just override the physbits.*

*Two possible workarounds come to mind:*
* *Is there some command line option that would allow me to override the MMIO window size? (basically bypassing the DynamicMMIOWindowSize heuristic without having to switch OVMF versions)*
* *Alternatively, is there a way to override the virtual address bits in the same way as we can for the physical bits, via some command line option?*

* *I ask this because I notice that when I disable host passthrough *(which works with my GPUs and results in a fast boot if `pci=realloc pci=nocrs` are used)* , my VM shows "Address sizes: 40 bits physical, 48 bits virtual", but when I use host passthrough and only override the physbits (which fails as described above), my VM shows "Address sizes: 40 bits physical, 57 bits virtual". (so I'm wondering if that could be a factor here.)*

* *(context: we do need CPU host passthrough for our use case)*

Thanks,
Mitchell Augustin


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