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: 633c8e9800f3 ("powerpc/pseries: Enable hardlockup watchdog for PowerVM
partitions")
Cc: sta...@vger.kernel.org # v5.14+
Signed-off-by: Gautam Menghani <gau...@linux.ibm.com>
---
v1 -> v2:
1. Call check_kvm_guest() call in disable_hardlockup_detector() instead
of relying on pSeries_smp_probe()
2. Add the fixes and stable tags
3. Some changes in patch description
arch/powerpc/kernel/setup_64.c | 1 +
1 file changed, 1 insertion(+)
diff --git a/arch/powerpc/kernel/setup_64.c b/arch/powerpc/kernel/setup_64.c
index 22f83fbbc762..1edc7cd68c10 100644
--- a/arch/powerpc/kernel/setup_64.c
+++ b/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();
}
--
2.47.0
