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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Hello!

There has been some great progress on this in the kernel over the past couple months, so I wanted to provide an update on the resolution here for any past/future readers of this thread.

There is now a patch series ( https://lore.kernel.org/all/20250205231728.2527186-1-alex.williamson@redhat.com/ ) under review to fix the root cause of this issue in the kernel. In my tests, when this series is applied on both the host and guest kernels of an affected system, it eliminates the extra boot time entirely.

The complete solution in the series above relies on huge pfnmap support, but older pre-huge-pfnmap kernels will still be able to benefit from this patch set ( https://lore.kernel.org/all/20250111210652.402845-1-alex.williamson@redhat.com/ ) , which eliminates about half of the excess boot time by removing many redundant decode disable/enable toggles during initialization.

Thanks,
Mitchell Augustin


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