powerpc/pseries: Fix KVM guest detection for disabling hardlockup det…

…ector

As per the kernel documentation[1], hardlockup detector should
be disabled in KVM guests as it may give false positives. On
PPC, hardlockup detector is enabled inside KVM guests because
disable_hardlockup_detector() is marked as early_initcall and it
relies on kvm_guest static key (is_kvm_guest()) which is initialized
later during boot by check_kvm_guest(), which is a core_initcall.
check_kvm_guest() is also called in pSeries_smp_probe(), which is called
before initcalls, but it is skipped if KVM guest does not have doorbell
support or if the guest is launched with SMT=1.

Call check_kvm_guest() in disable_hardlockup_detector() so that
is_kvm_guest() check goes through fine and hardlockup detector can be
disabled inside the KVM guest.

[1]: Documentation/admin-guide/sysctl/kernel.rst

Fixes: 633c8e9 ("powerpc/pseries: Enable hardlockup watchdog for PowerVM partitions")
Cc: [email protected] # v5.14+
Signed-off-by: Gautam Menghani <[email protected]>
Signed-off-by: Michael Ellerman <[email protected]>
Link: https://patch.msgid.link/[email protected]

arch/powerpc/kernel/setup_64.c

@@ -920,6 +920,7 @@ static int __init disable_hardlockup_detector(void)
 	hardlockup_detector_disable();
 #else
 	if (firmware_has_feature(FW_FEATURE_LPAR)) {
+		check_kvm_guest();
 		if (is_kvm_guest())
 			hardlockup_detector_disable();
 	}