linux-kernel - RE: [PATCH] efi: Free existing memory map before installing new memory map

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Date:   Wed, 27 Jun 2018 07:28:01 +0000
From:   "Prakhya, Sai Praneeth" <sai.praneeth.prakhya@...el.com>
To:     Ard Biesheuvel <ard.biesheuvel@...aro.org>
CC:     linux-efi <linux-efi@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Lee Chun-Yi <jlee@...e.com>, Borislav Petkov <bp@...en8.de>,
        Dave Young <dyoung@...hat.com>,
        Laszlo Ersek <lersek@...hat.com>,
        Bhupesh Sharma <bhsharma@...hat.com>,
        "Neri, Ricardo" <ricardo.neri@...el.com>,
        "Shankar, Ravi V" <ravi.v.shankar@...el.com>,
        Matt Fleming <matt@...eblueprint.co.uk>
Subject: RE: [PATCH] efi: Free existing memory map before installing new
 memory map

> > Also, could you please clarify if there is any specific reason why
> > memory allocated using memblock_reserve() shouldn't be freed. I mean,
> > not with memblock_free() but I think we could make it _available_
> > using free_bootmem() (or something similar, please correct me if this is not
> the right API).
> 
> On arm64, the memory map is provided to the core kernel by the stub, and after
> kexec, a pointer to the same memory map will be passed to the next kernel. So
> the kernel does not 'own' that allocation, and it should not free it or overwrite
> it.

Thanks for the reply. It confirms that the issue is only on x86 systems.
I see that arm64 doesn't call efi_memmap_alloc() and hence there is no concept 
of allocating memory for new memory map and installing it (so no memory leak).

Regards,
Sai