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To: Mahesh Salgaonkar <mahesh@linux.vnet.ibm.com>,
 linuxppc-dev <linuxppc-dev@ozlabs.org>, Paul Mackerras <paulus@samba.org>
From: Michael Ellerman <mpe@ellerman.id.au>
Cc: KVM <kvm@vger.kernel.org>, KVM-PPC <kvm-ppc@vger.kernel.org>
Subject: Re: [1/3] Powernv: Remove the usage of PACAR1 from opal wrappers
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Date: Fri, 18 Mar 2016 14:33:31 +1100 (AEDT)
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On Thu, 2016-14-01 at 03:14:58 UTC, Mahesh Salgaonkar wrote:
> From: Mahesh Salgaonkar <mahesh@linux.vnet.ibm.com>
> 
> OPAL_CALL wrapper code sticks the r1 (stack pointer) into PACAR1 purely
> for debugging purpose only. The power7_wakeup* functions relies on stack
> pointer saved in PACAR1. Any opal call made using opal wrapper (directly
> or in-directly) before we fall through power7_wakeup*, then it ends up
> replacing r1 in PACAR1(r13) leading to kernel panic. So far we don't see
> any issues because we have never made any opal calls using OPAL wrapper
> before power7_wakeup*. But the subsequent HMI patch would need to invoke
> C calls during cpu wakeup/idle path that in-directly makes opal call using
> opal wrapper. This patch facilitates the subsequent HMI patch by removing
> usage of PACAR1 from opal call wrapper.
> 
> Signed-off-by: Mahesh Salgaonkar <mahesh@linux.vnet.ibm.com>

Acked-by: Michael Ellerman <mpe@ellerman.id.au>

cheers