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In-Reply-To: <20160407215811.8404.6733.stgit@hbathini.in.ibm.com>
To: Hari Bathini <hbathini@linux.vnet.ibm.com>,
 linuxppc-dev <linuxppc-dev@ozlabs.org>
From: Michael Ellerman <mpe@ellerman.id.au>
Cc: Michael Neuling <mikey@neuling.org>,
 Mahesh J Salgaonkar <mahesh@linux.vnet.ibm.com>,
 Paul Mackerras <paulus@samba.org>
Subject: Re: [v4,
 2/3] ppc64/book3s: make some room for common interrupt vector code
Message-Id: <3qmZVp4lgdz9t5C@ozlabs.org>
Date: Fri, 15 Apr 2016 21:06:58 +1000 (AEST)
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Hi Hari,

Thanks for persisting with this.

On Thu, 2016-07-04 at 21:58:50 UTC, Hari Bathini wrote:
> With the previous patch, we choke out whatever little space is left
> below 0x7000 (FWNMI hard block) while there is a hole of ~1400 bytes
> below __end_interrupts marker when CONFIG_CBE_RAS is disabled.
> Considering CONFIG_CBE_RAS is not enabled by default for BOOK3S, this
> is not a desirable scenario especially when we have to worry about
> each additional instruction that goes below 0x7000.
> 
> Memory region from 0x1800 to 0x4000 is dedicated for common interrupt
> vector code. Also, we never hit an interrupt below 0x300 when IR=DR=1
> implying memory region between 0x4000 to 0x4300 can also be used for
> common interrupt vector code. So, we can effectively use memory region
> between 0x1800 to 0x4300 for common interrupt vector code.

On Power9 the system-call-vectored instruction will use the region at 0x3000, so
moving code into that space is not a good long term plan.

I'll take your v2 and put it in next next week.

cheers