Messages in this thread Patch in this message | | | Date | Mon, 23 Jan 2012 15:39:53 -0800 | From | Greg KH <> | Subject | [67/90] intel idle: Make idle driver more robust |
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3.0-stable review patch. If anyone has any objections, please let me know.
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From: Thomas Renninger <trenn@suse.de>
commit 5c2a9f06a9cd7194f884cdc88144866235dec07d upstream.
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
Signed-off-by: Thomas Renninger <trenn@suse.de> CC: Bruno Friedmann <bruno@ioda-net.ch> Signed-off-by: Len Brown <len.brown@intel.com> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
--- drivers/idle/intel_idle.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-)
--- a/drivers/idle/intel_idle.c +++ b/drivers/idle/intel_idle.c @@ -321,7 +321,8 @@ 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);
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