Re: [RFT] kvm with Windows optimization

Anthony Liguori
2007-10-25T18:27:47Z

Avi Kivity wrote:
> This is a request for testing of an experimental kvm feature that
> dramatically accelerates some Windows releases (when running with the
> ACPI HAL, and especially with guest SMP). The feature detects accesses
> by the guest to the Task Priority Register (TPR) and patches them at
> runtime to a kvm-friendly code snipped that is provided by the BIOS.
>
> The upshot of all that is that
> http://kvm.qumranet.com/kvmwiki/Windows_ACPI_Workaround is no longer
> required, and Windows SMP no longer runs like a dog; it's quite snappy
> from my very limited testing.
>
> Please download the test release from
> http://people.qumranet.com/avi/tpr-opt-1.tar.gz and give it a spin.
> Once it has received some exposure, I'll merge it into mainline.
>
> Credit for the original idea is due to Ben Serebrin.
>

BTW, is it wise to enable this by default for all guests? Ignoring the
fact that we're modifying guest's memory without its knowledge, if a
guest unmaps the VA mappings for the BIOS then all sorts of problems
could occur.

Regards,

Anthony Liguori