linux-kernel - Re: [PATCH 00/15] powerpc/watchpoint: Preparation for more than one watchpoint

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Message-Id: <27a3c6c0-3880-406a-3e1e-ccb017e5a77c@linux.ibm.com>
Date:   Mon, 23 Mar 2020 19:07:32 +0530
From:   Ravi Bangoria <ravi.bangoria@...ux.ibm.com>
To:     Christophe Leroy <christophe.leroy@....fr>
Cc:     mpe@...erman.id.au, mikey@...ling.org, apopple@...ux.ibm.com,
        paulus@...ba.org, npiggin@...il.com,
        naveen.n.rao@...ux.vnet.ibm.com, peterz@...radead.org,
        jolsa@...nel.org, oleg@...hat.com, fweisbec@...il.com,
        mingo@...nel.org, linuxppc-dev@...ts.ozlabs.org,
        linux-kernel@...r.kernel.org,
        Ravi Bangoria <ravi.bangoria@...ux.ibm.com>
Subject: Re: [PATCH 00/15] powerpc/watchpoint: Preparation for more than one
 watchpoint



On 3/18/20 6:22 PM, Ravi Bangoria wrote:
> 
> 
> On 3/16/20 8:35 PM, Christophe Leroy wrote:
>>
>>
>> Le 09/03/2020 à 09:57, Ravi Bangoria a écrit :
>>> So far, powerpc Book3S code has been written with an assumption of only
>>> one watchpoint. But future power architecture is introducing second
>>> watchpoint register (DAWR). Even though this patchset does not enable
>>> 2nd DAWR, it make the infrastructure ready so that enabling 2nd DAWR
>>> should just be a matter of changing count.
>>
>> Some book3s (e300 family for instance, I think G2 as well) already have a DABR2 in addition to DABR.
>> Will this series allow to use it as well ?
> 
> I wasn't aware of that. I'll take a look at their specs and check if they
> can piggyback on this series for 2nd DABR.

There are some differences between G2/e300 DABRs and Book3S DAWRs. G2/e300
DABRs provides some functionalities like "Match if EA less/greater than DABR",
"combined mode" etc. are not present with DAWRs. DBCR on G2/e300 also provides
which DABR caused the exception. So this series might not directly allow to
use DABR2 but, I guess, it should work as base infrastructure.

Ravi