x86/acpi: Don't limit CPUs to 1 for Xen PV guests due to disabled ACPI

Xen disables ACPI for PV guests in DomU, which causes acpi_mps_check() to
return 1 when CONFIG_X86_MPPARSE is not set. As a result, the local APIC is
disabled and the guest is later limited to a single vCPU, despite being
configured with more.

This regression was introduced in version 6.9 in commit 7c0edad3643f
("x86/cpu/topology: Rework possible CPU management"), which added an
early check that limits CPUs to 1 if apic_is_disabled.

Update the acpi_mps_check() logic to return 0 early when running as a Xen
PV guest in DomU, preventing APIC from being disabled in this specific case
and restoring correct multi-vCPU behaviour.

Fixes: 7c0edad3643f ("x86/cpu/topology: Rework possible CPU management")
Signed-off-by: Petr Vaněk <[email protected]>
Signed-off-by: Thomas Gleixner <[email protected]>
Link: https://lore.kernel.org/all/[email protected]

0 files changed, 0 insertions, 0 deletions