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Subject: Re: [PATCH v4 0/5] Powerpc/Watchpoint: Few important fixes
To:     Christophe Leroy <christophe.leroy@c-s.fr>
Cc:     mpe@ellerman.id.au, mikey@neuling.org, npiggin@gmail.com,
        benh@kernel.crashing.org, paulus@samba.org,
        naveen.n.rao@linux.vnet.ibm.com, linuxppc-dev@lists.ozlabs.org,
        linux-kernel@vger.kernel.org,
        Ravi Bangoria <ravi.bangoria@linux.ibm.com>
References: <20190925040630.6948-1-ravi.bangoria@linux.ibm.com>
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 <3e31e5f7-f948-512a-054c-9ad10103ccc0@linux.ibm.com>
From:   Ravi Bangoria <ravi.bangoria@linux.ibm.com>
Date:   Thu, 10 Oct 2019 11:55:54 +0530
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On 10/10/19 10:14 AM, Ravi Bangoria wrote:
> 
>>> @Christophe, Is patch5 works for you on 8xx?
>>>
>>
>> Getting the following :
>>
>> root@vgoip:~# ./ptrace-hwbreak
>> test: ptrace-hwbreak
>> tags: git_version:v5.4-rc2-710-gf0082e173fe4-dirty
>> PTRACE_SET_DEBUGREG, WO, len: 1: Ok
>> PTRACE_SET_DEBUGREG, WO, len: 2: Ok
>> PTRACE_SET_DEBUGREG, WO, len: 4: Ok
>> PTRACE_SET_DEBUGREG, WO, len: 8: Ok
>> PTRACE_SET_DEBUGREG, RO, len: 1: Ok
>> PTRACE_SET_DEBUGREG, RO, len: 2: Ok
>> PTRACE_SET_DEBUGREG, RO, len: 4: Ok
>> PTRACE_SET_DEBUGREG, RO, len: 8: Ok
>> PTRACE_SET_DEBUGREG, RW, len: 1: Ok
>> PTRACE_SET_DEBUGREG, RW, len: 2: Ok
>> PTRACE_SET_DEBUGREG, RW, len: 4: Ok
>> PTRACE_SET_DEBUGREG, RW, len: 8: Ok
>> PPC_PTRACE_SETHWDEBUG, MODE_EXACT, WO, len: 1: Ok
>> PPC_PTRACE_SETHWDEBUG, MODE_EXACT, RO, len: 1: Ok
>> PPC_PTRACE_SETHWDEBUG, MODE_EXACT, RW, len: 1: Ok
>> PPC_PTRACE_SETHWDEBUG, MODE_RANGE, DW ALIGNED, WO, len: 6: Ok
>> PPC_PTRACE_SETHWDEBUG, MODE_RANGE, DW ALIGNED, RO, len: 6: Fail
>> failure: ptrace-hwbreak
>>
> 
> Thanks Christophe. I don't have any 8xx box. I checked qemu and it seems
> qemu emulation for 8xx is not yet supported. So I can't debug this. Can
> you please check why it's failing?

PPC_PTRACE_SETHWDEBUG internally uses DAWR register and probably 8xx does
not emulate DAWR logic, it only uses DABR to emulate double-word watchpoint.
In that case, all testcases that uses PPC_PTRACE_SETHWDEBUG should be
disabled for 8xx. I'll change [PATCH 5] accordingly and resend.

Also, do you think I should fix hw_breakpoint_validate_len() from [PARCH 1]
for 8xx? I re-checked you recent patch* to allow any address range size for
8xx. With that patch, hw_breakpoint_validate_len() won't get called at all
for 8xx.

* Message-Id: 1ed0de54ce6021fa0fdf50e938365546a4f5e316.1566925030.git.christophe.leroy@c-s.fr

-Ravi