linux-kernel - Re: [RFC PATCH 2/4] of: Add a common kexec FDT setup function

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Date:   Fri, 11 Dec 2020 23:17:02 -0300
From:   Thiago Jung Bauermann <bauerman@...ux.ibm.com>
To:     Lakshmi Ramasubramanian <nramas@...ux.microsoft.com>
Cc:     Rob Herring <robh@...nel.org>, takahiro.akashi@...aro.org,
        will@...nel.org, catalin.marinas@....com, mpe@...erman.id.au,
        zohar@...ux.ibm.com, james.morse@....com, sashal@...nel.org,
        benh@...nel.crashing.org, paulus@...ba.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,
        masahiroy@...nel.org, bhsharma@...hat.com, mbrugger@...e.com,
        hsinyi@...omium.org, tao.li@...o.com, christophe.leroy@....fr,
        linux-integrity@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, devicetree@...r.kernel.org,
        prsriva@...ux.microsoft.com, balajib@...ux.microsoft.com
Subject: Re: [RFC PATCH 2/4] of: Add a common kexec FDT setup function


Lakshmi Ramasubramanian <nramas@...ux.microsoft.com> writes:

> On 12/11/20 2:10 PM, Rob Herring wrote:
>
> Hi Rob,
>
>> Both arm64 and powerpc do essentially the same FDT /chosen setup for
>> kexec. We can simply combine everything each arch does. The differences
>> are either omissions that arm64 should have or additional properties
>> that will be ignored.
>> The differences relative to the arm64 version:
>> - If /chosen doesn't exist, it will be created (should never happen).
>> - Any old dtb and initrd reserved memory will be released.
>> - The new initrd and elfcorehdr are marked reserved.
>> - "linux,booted-from-kexec" is set.
>> The differences relative to the powerpc version:
>> - "kaslr-seed" and "rng-seed" may be set.
>> - "linux,elfcorehdr" is set.
>> - Any existing "linux,usable-memory-range" is removed.
>> Signed-off-by: Rob Herring <robh@...nel.org>
>> ---
>> This could be taken a step further and do the allocation of the new
>> FDT. The difference is arm64 uses vmalloc and powerpc uses kmalloc. The
>> arm64 version also retries with a bigger allocation. That seems
>> unnecessary.
>> ---
>>   drivers/of/Makefile |   1 +
>>   drivers/of/kexec.c  | 228 ++++++++++++++++++++++++++++++++++++++++++++
>>   include/linux/of.h  |   5 +
>>   3 files changed, 234 insertions(+)
>>   create mode 100644 drivers/of/kexec.c
>> diff --git a/drivers/of/Makefile b/drivers/of/Makefile
>> index 6e1e5212f058..8ce11955afde 100644
>> --- a/drivers/of/Makefile
>> +++ b/drivers/of/Makefile
>> @@ -13,5 +13,6 @@ obj-$(CONFIG_OF_RESERVED_MEM) += of_reserved_mem.o
>>   obj-$(CONFIG_OF_RESOLVE)  += resolver.o
>>   obj-$(CONFIG_OF_OVERLAY) += overlay.o
>>   obj-$(CONFIG_OF_NUMA) += of_numa.o
>> +obj-$(CONFIG_KEXEC_FILE) += kexec.o
>
> For the functions moved from powerpc & arm64 to "drivers/of/kexec.c" in this
> patch, compiling kexec.c when CONFIG_KEXEC_FILE is enabled is fine. But when
> more functions (such as remove_ima_buffer()) are moved to this file, Makefile
> needs to be updated for other ima kexec related CONFIGs.

IMA kexec is only available if CONFIG_KEXEC_FILE is enabled, so I don't
understand what problem you are seeing.

-- 
Thiago Jung Bauermann
IBM Linux Technology Center