[PATCH] powerpc/mce: check if event info is valid

[Michael Ellerman]

Ganesh <ganeshgr at linux.ibm.com> writes:
> On 8/6/21 6:53 PM, Ganesh Goudar wrote:
>
>> Check if the event info is valid before printing the
>> event information. When a fwnmi enabled nested kvm guest
>> hits a machine check exception L0 and L2 would generate
>> machine check event info, But L1 would not generate any
>> machine check event info as it won't go through 0x200
>> vector and prints some unwanted message.
>>
>> To fix this, 'in_use' variable in machine check event info is
>> no more in use, rename it to 'valid' and check if the event
>> information is valid before logging the event information.
>>
>> without this patch L1 would print following message for
>> exceptions encountered in L2, as event structure will be
>> empty in L1.
>>
>> "Machine Check Exception, Unknown event version 0".
>>
>> Signed-off-by: Ganesh Goudar <ganeshgr at linux.ibm.com>
>> ---
>
> Hi mpe, Any comments on this patch.

The variable rename is a bit of a distraction.

But ignoring that, how do we end up processing a machine_check_event
that has in_use = 0?

You don't give much detail on what call path you're talking about. I
guess we're coming in via the calls in the KVM code?

In the definition of kvm_vcpu_arch we have:

	struct machine_check_event mce_evt; /* Valid if trap == 0x200 */

And you said we're not going via 0x200 in L1. But so shouldn't we be
teaching the KVM code not to use mce_evt when trap is not 0x200?

cheers