Re: Re: [RESEND PATCH v5 5/5] Documentation/vmcoreinfo: Add documentation for 'TCR_EL1.T1SZ'

From: Scott Branden <scott.branden@broadcom.com>
To: Bhupesh Sharma <bhsharma@redhat.com>,
	James Morse <james.morse@arm.com>,
	linux-kernel@vger.kernel.org
Cc: Mark Rutland <mark.rutland@arm.com>,
	Ard Biesheuvel <ard.biesheuvel@linaro.org>,
	linux-doc@vger.kernel.org,
	Catalin Marinas <catalin.marinas@arm.com>,
	x86@kernel.org, kexec@lists.infradead.org,
	linuxppc-dev@lists.ozlabs.org,
	Kazuhito Hagio <k-hagio@ab.jp.nec.com>,
	Dave Anderson <anderson@redhat.com>,
	bhupesh.linux@gmail.com, Will Deacon <will@kernel.org>,
	linux-arm-kernel@lists.infradead.org,
	Steve Capper <steve.capper@arm.com>
Subject: Re: Re: [RESEND PATCH v5 5/5] Documentation/vmcoreinfo: Add documentation for 'TCR_EL1.T1SZ'
Date: Wed, 3 Jun 2020 11:47:28 -0700	[thread overview]
Message-ID: <51606585-77a3-265f-1d4e-19f25a90697d@broadcom.com> (raw)
In-Reply-To: <b7d8d603-d9fe-3e18-c754-baf2015acd16@redhat.com>

Hi Bhupesh,

Would be great to get this patch series upstreamed?

On 2019-12-25 10:49 a.m., Bhupesh Sharma wrote:
> Hi James,
>
> On 12/12/2019 04:02 PM, James Morse wrote:
>> Hi Bhupesh,
>
> I am sorry this review mail skipped my attention due to holidays and 
> focus on other urgent issues.
>
>> On 29/11/2019 19:59, Bhupesh Sharma wrote:
>>> Add documentation for TCR_EL1.T1SZ variable being added to
>>> vmcoreinfo.
>>>
>>> It indicates the size offset of the memory region addressed by 
>>> TTBR1_EL1
>>
>>> and hence can be used for determining the vabits_actual value.
>>
>> used for determining random-internal-kernel-variable, that might not 
>> exist tomorrow.
>>
>> Could you describe how this is useful/necessary if a debugger wants 
>> to walk the page
>> tables from the core file? I think this is a better argument.
>>
>> Wouldn't the documentation be better as part of the patch that adds 
>> the export?
>> (... unless these have to go via different trees? ..)
>
> Ok, will fix the same in v6 version.
>
>>> diff --git a/Documentation/admin-guide/kdump/vmcoreinfo.rst 
>>> b/Documentation/admin-guide/kdump/vmcoreinfo.rst
>>> index 447b64314f56..f9349f9d3345 100644
>>> --- a/Documentation/admin-guide/kdump/vmcoreinfo.rst
>>> +++ b/Documentation/admin-guide/kdump/vmcoreinfo.rst
>>> @@ -398,6 +398,12 @@ KERNELOFFSET
>>>   The kernel randomization offset. Used to compute the page offset. If
>>>   KASLR is disabled, this value is zero.
>>>   +TCR_EL1.T1SZ
>>> +------------
>>> +
>>> +Indicates the size offset of the memory region addressed by TTBR1_EL1
>>
>>> +and hence can be used for determining the vabits_actual value.
>>
>> 'vabits_actual' may not exist when the next person comes to read this 
>> documentation (its
>> going to rot really quickly).
>>
>> I think the first half of this text is enough to say what this is 
>> for. You should include
>> words to the effect that its the hardware value that goes with 
>> swapper_pg_dir. You may
>> want to point readers to the arm-arm for more details on what the 
>> value means.
>
> Ok, got it. Fixed this in v6, which should be on its way shortly.
I can't seem to find v6?
>
> Thanks,
> Bhupesh
>
>
> _______________________________________________
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>

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