From: Thomas Renninger <trenn@xxxxxxx> kvm -cpu host passes the original cpuid info to the guest. Latest kvm version seem to return true for mwait_leaf cpuid function on recent Intel CPUs. But it does not return mwait C-states (mwait_substates), instead zero is returned. While real CPUs seem to always return non-zero values, the intel idle driver should not get active in kvm (mwait_substates == 0) case and bail out. Otherwise a Null pointer exception will happen later when the cpuidle subsystem tries to get active: [0.984807] BUG: unable to handle kernel NULL pointer dereference at (null) [0.984807] IP: [<(null)>] (null) ... [0.984807][<ffffffff8143cf34>] ? cpuidle_idle_call+0xb4/0x340 [0.984807][<ffffffff8159e7bc>] ? __atomic_notifier_call_chain+0x4c/0x70 [0.984807][<ffffffff81001198>] ? cpu_idle+0x78/0xd0 Reference: https://bugzilla.novell.com/show_bug.cgi?id=726296 Cc: stable@xxxxxxxxxxxxxxx Signed-off-by: Thomas Renninger <trenn@xxxxxxx> CC: Bruno Friedmann <bruno@xxxxxxxxxxx> Signed-off-by: Len Brown <len.brown@xxxxxxxxx> --- drivers/idle/intel_idle.c | 3 ++- 1 files changed, 2 insertions(+), 1 deletions(-) diff --git a/drivers/idle/intel_idle.c b/drivers/idle/intel_idle.c index 6a3d91d..e56ae0b 100644 --- a/drivers/idle/intel_idle.c +++ b/drivers/idle/intel_idle.c @@ -356,7 +356,8 @@ static int intel_idle_probe(void) cpuid(CPUID_MWAIT_LEAF, &eax, &ebx, &ecx, &mwait_substates); if (!(ecx & CPUID5_ECX_EXTENSIONS_SUPPORTED) || - !(ecx & CPUID5_ECX_INTERRUPT_BREAK)) + !(ecx & CPUID5_ECX_INTERRUPT_BREAK) || + !mwait_substates) return -ENODEV; pr_debug(PREFIX "MWAIT substates: 0x%x\n", mwait_substates); -- 1.7.9.rc1 _______________________________________________ linux-pm mailing list linux-pm@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linuxfoundation.org/mailman/listinfo/linux-pm
