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Subject: Re: [v3 PATCH 2/5] powerpc/pseries: Fix endainness while restoring of
 r3 in MCE handler.
To: Michael Ellerman <mpe@ellerman.id.au>,
        linuxppc-dev <linuxppc-dev@ozlabs.org>
Cc: stable@vger.kernel.org,
        "Aneesh Kumar K.V" <aneesh.kumar@linux.vnet.ibm.com>,
        Laurent Dufour <ldufour@linux.vnet.ibm.com>,
        Nicholas Piggin <npiggin@gmail.com>
References: <152839244928.25118.15100234720683911223.stgit@jupiter.in.ibm.com>
 <152839249913.25118.1191250274945665204.stgit@jupiter.in.ibm.com>
 <87fu1xvkjc.fsf@concordia.ellerman.id.au>
From: Mahesh Jagannath Salgaonkar <mahesh@linux.vnet.ibm.com>
Date: Fri, 8 Jun 2018 16:01:21 +0530
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On 06/08/2018 12:20 PM, Michael Ellerman wrote:
> Mahesh J Salgaonkar <mahesh@linux.vnet.ibm.com> writes:
>> From: Mahesh Salgaonkar <mahesh@linux.vnet.ibm.com>
>>
>> During Machine Check interrupt on pseries platform, register r3 points
>> RTAS extended event log passed by hypervisor. Since hypervisor uses r3
>> to pass pointer to rtas log, it stores the original r3 value at the
>> start of the memory (first 8 bytes) pointed by r3. Since hypervisor
>> stores this info and rtas log is in BE format, linux should make
>> sure to restore r3 value in correct endian format.
> 
> Can we hit this under KVM? And if so what if the KVM/qemu is running
> little endian, does it still write the value BE?

FWNMI support for qemu is still not in. But when it is in, we can hit
this. But whenever FWNMI support gets in, it should pass RTAS event data
always in BE format including original r3 value.

Thanks,
-Mahesh.
> 
> cheers
>