linux-kernel - Re: [PATCH v8 1/4] powerpc: Refactor kexec functions to move arch independent code to drivers/of

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Message-ID: <4f308bc7-81ee-6a16-0098-884005e6296a@linux.microsoft.com>
Date:   Tue, 3 Nov 2020 12:07:11 -0800
From:   Lakshmi Ramasubramanian <nramas@...ux.microsoft.com>
To:     Mimi Zohar <zohar@...ux.ibm.com>, bauerman@...ux.ibm.com,
        robh@...nel.org, gregkh@...uxfoundation.org, james.morse@....com,
        catalin.marinas@....com, sashal@...nel.org, will@...nel.org,
        mpe@...erman.id.au, benh@...nel.crashing.org, paulus@...ba.org,
        robh+dt@...nel.org, frowand.list@...il.com,
        vincenzo.frascino@....com, mark.rutland@....com,
        dmitry.kasatkin@...il.com, jmorris@...ei.org, serge@...lyn.com,
        pasha.tatashin@...een.com, allison@...utok.net,
        kstewart@...uxfoundation.org, takahiro.akashi@...aro.org,
        tglx@...utronix.de, masahiroy@...nel.org, bhsharma@...hat.com,
        mbrugger@...e.com, hsinyi@...omium.org, tao.li@...o.com,
        christophe.leroy@....fr
Cc:     linux-integrity@...r.kernel.org, linux-kernel@...r.kernel.org,
        devicetree@...r.kernel.org, prsriva@...ux.microsoft.com,
        balajib@...ux.microsoft.com
Subject: Re: [PATCH v8 1/4] powerpc: Refactor kexec functions to move arch
 independent code to drivers/of

On 11/3/20 11:59 AM, Mimi Zohar wrote:
> On Tue, 2020-11-03 at 11:15 -0800, Lakshmi Ramasubramanian wrote:
>> On 11/3/20 6:55 AM, Mimi Zohar wrote:
>>
>> Hi Mimi,
>>
>> Thanks for reviewing the patches.
>>
>>> On Fri, 2020-10-30 at 10:44 -0700, Lakshmi Ramasubramanian wrote:
>>>> The functions remove_ima_buffer() and delete_fdt_mem_rsv() that handle
>>>> carrying forward the IMA measurement logs on kexec for powerpc do not
>>>> have architecture specific code, but they are currently defined for
>>>> powerpc only.
>>>
>>> ^ ... logs on kexec, do not have architecture specific code, but are
>>> currently limited to powerpc.
>> Will make this change.
>>
>>>
>>>>
>>>> remove_ima_buffer() and delete_fdt_mem_rsv() are used to remove
>>>> the IMA log entry from the device tree and free the memory reserved
>>>> for the log. These functions need to be defined even if the current
>>>> kernel does not support carrying forward IMA log across kexec since
>>>> the previous kernel could have supported that and therefore the current
>>>> kernel needs to free the allocation.
>>>
>>> The first paragraph describes these function as "handle carrying
>>> forward the IMA measurement logs on kexec", while this paragraph says
>>> "are used to remove the IMA log entry".  Consider listing all of the
>>> functions being moved in the first paragrah, then "handle carrying
>>> forward" could be expanded to "carrying ... and removing".
>> Sure.
> 
> Sorry, even with naming do_get_kexec_buffer(), the measurement list
> isn't being carried across kexec.   Please adjust the wording.
Sure - will update.

> 
>>
>>>
>>>>
>>>> Rename remove_ima_buffer() to remove_ima_kexec_buffer().
>>>> Define remove_ima_kexec_buffer() and delete_fdt_mem_rsv() in
>>>> drivers/of/fdt.c. A later patch in this series will use these functions
>>>> to free the allocation, if any, made by the previous kernel for ARM64.
>>>
>>> - ^Define -> Move
>>> - Three functions are being moved, but only two are listed.
>>> "do_get_kexec_buffer" is not mentioned.
>>> - Don't refer to a later patch, but explain the purpose here.  For
>>> example, "Move ... , making them accessible to other archs."
>> Sure.
>>
>>>
>>>>
>>>> Define FDT_PROP_IMA_KEXEC_BUFFER for the chosen node, namely
>>>> "linux,ima-kexec-buffer", that is added to the DTB to hold
>>>> the address and the size of the memory reserved to carry
>>>> the IMA measurement log.
>>>
>>> The above two paragraphs describe renaming a function and defining a
>>> chosen node.  These two preparatory changes should be made,
>>> independently of each other, prior to this patch.  This patch should be
>>> limited to moving code, with the subject line truncated to "move arch
>>> independent code to drivers/of".
>>>
>>
>> Just to be clear -
>>
>> Split this patch into 3 parts as listed below:
>>
>> PATCH #1: Rename remove_ima_buffer() to remove_ima_kexec_buffer()
>> PATCH #2: Define the chosen node
>> PATCH #3: Move the functions to drivers/of/fdt.c
> 
> yes, thanks.

thanks,
  -lakshmi