Re: [PATCH] x86/xen: disable CPU idle and frequency drivers for PVH dom0

[Jason Andryuk]

On 2025-04-07 06:18, Roger Pau Monne wrote:
> When running as a PVH dom0 the ACPI tables exposed to Linux are (mostly)
> the native ones, thus exposing the C and P states, that can lead to
> attachment of CPU idle and frequency drivers.  However the entity in
> control of the CPU C and P states is Xen, as dom0 doesn't have a full view
> of the system load, neither has all CPUs assigned and identity pinned.
>
> Like it's done for classic PV guests, prevent Linux from using idle or
> frequency state drivers when running as a PVH dom0.
>
> On an AMD EPYC 7543P system without this fix a Linux PVH dom0 will keep the
> host CPUs spinning at 100% even when dom0 is completely idle, as it's
> attempting to use the acpi_idle driver.
>
> Signed-off-by: Roger Pau Monné <roger.pau@xxxxxxxxxx>

Reviewed-by: Jason Andryuk <jason.andryuk@xxxxxxx>

Thanks,
Jason