[PATCH] arm64/efi: register UEFI runtime mmio regions as iomem resources

[Ard Biesheuvel]

On 27 October 2015 at 13:31, Ard Biesheuvel <ard.biesheuvel at linaro.org> wrote:
> On 27 October 2015 at 21:08, Linus Walleij <linus.walleij at linaro.org> wrote:
>> On Mon, Oct 26, 2015 at 9:41 AM, Ard Biesheuvel
>> <ard.biesheuvel at linaro.org> wrote:
>>
>>> In order to prevent kernel drivers from attaching to MMIO regions
>>> that are owned by the firmware, register them as iomem resources.
>>>
>>> Signed-off-by: Ard Biesheuvel <ard.biesheuvel at linaro.org>
>>
>> Is this related to the flash memory discussion so that NOR flash
>> will be part of what is considered "I/O memory"
>
> Yes
>
>> and flash
>> protection achieved this way?
>>
>
> ... and no, not entirely. Note that this is not about 'protecting' the
> flash in a security sense. It is simply to reserve the resources that
> should be considered occupied by the UEFI firmware drivers. This may
> be NOR flash, but it may just as well be the RTC or potentially a
> syscon register block to do reset and/or poweroff.
>
> My QEMU mach-virt /proc/iomem looks like this with the patch applied:
>
> 04000000-07ffffff : UEFI Runtime MMIO
> 09000000-09000fff : /pl011 at 9000000
>   09000000-09000fff : /pl011 at 9000000
> 09010000-0901ffff : UEFI Runtime MMIO
> 40000000-7fffffff : System RAM
>   40080000-408a27d3 : Kernel code
>   40970000-40adffff : Kernel data
>
> where the first UEFI mmio region is the second bank of NOR flash (the
> first one holds the firmware image itself, so that is not claimed
> since the variable store driver never accesses it) and the second UEFI
> mmio region is the PL031 RTC.
>

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