Re: [RFC PATCH 7/9] powerpc: Decode and save machine check event.

On Wed, Aug 07, 2013 at 03:09:13PM +0530, Mahesh J Salgaonkar wrote:

From: Mahesh Salgaonkar <redacted>

Now that we handle machine check in linux, the MCE decoding should also
take place in linux host. This info is crucial to log before we go down
in case we can not handle the machine check errors. This patch decodes
and populates a machine check event which contain high level meaning full
MCE information.

A couple of things worry me about this patch:

First, there is the fact that we can only do get_mce_event() once for
a given machine check.  You call it in kvmppc_realmode_mc_power7(),
which is fine, but if it is not something we recognize and can handle
we will proceed to exit the guest and jump to machine_check_fwnmi,
which will then proceed to machine_check_common() and then
opal_machine_check(), where you have added another call to
get_mce_event(), which will probably underflow your little per-cpu
stack of machine check events.

Secondly, we shouldn't call save_mce_event() if we're not in
hypervisor mode, since per-cpu variables are not in general accessible
in real mode when running under a hypervisor with a limited real-mode
area (RMA).

Paul.