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| author | Thomas Renninger <trenn@suse.de> | 2011-12-04 22:17:29 +0100 |
|---|---|---|
| committer | Len Brown <len.brown@intel.com> | 2012-01-17 14:19:59 -0500 |
| commit | 5c2a9f06a9cd7194f884cdc88144866235dec07d (patch) | |
| tree | 226772f58c4a1727ff536913c69bab4b75f51427 /drivers/idle/intel_idle.c | |
| parent | 95e3ec11491d0cbce9fcdf1cc17a527c114c7dcf (diff) | |
| download | lwn-5c2a9f06a9cd7194f884cdc88144866235dec07d.tar.gz lwn-5c2a9f06a9cd7194f884cdc88144866235dec07d.zip | |
intel idle: Make idle driver more robust
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@vger.kernel.org
Signed-off-by: Thomas Renninger <trenn@suse.de>
CC: Bruno Friedmann <bruno@ioda-net.ch>
Signed-off-by: Len Brown <len.brown@intel.com>
Diffstat (limited to 'drivers/idle/intel_idle.c')
| -rw-r--r-- | 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 18f9ad814104..91aff180ac47 100644 --- a/drivers/idle/intel_idle.c +++ b/drivers/idle/intel_idle.c @@ -347,7 +347,8 @@ 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); |