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SubjectRe: [PATCH V2] ARM: dts: bcm283x: Reserve first page for firmware
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On 05/09/2017 02:04 AM, Phil Elwell wrote:
> The Raspberry Pi startup stub files for multi-core BCM27XX processors
> make the secondary CPUs spin until the corresponding mailbox is
> written. These stubs are loaded at physical address 0x00000xxx (as seen
> by the ARMs), but this page will be reused by the kernel unless it is
> explicitly reserved, causing the waiting cores to execute random code.
>
> Use the /memreserve/ Device Tree directive to mark the first page as
> off-limits to the kernel.

This reserves a 4KB page here, is this good enough, or should we just go
directly to the maximum page granule size possible on an ARM64/Linux
system to be on the safe side?

>
> See: https://github.com/raspberrypi/linux/issues/1989
>
> Signed-off-by: Phil Elwell <phil@raspberrypi.org>
> ---
>
> Changes in V2:
> - Rebase against linux-next
> - Drop downstream-only patch
>
> arch/arm/boot/dts/bcm283x.dtsi | 2 ++
> 1 file changed, 2 insertions(+)
>
> diff --git a/arch/arm/boot/dts/bcm283x.dtsi b/arch/arm/boot/dts/bcm283x.dtsi
> index a3106aa..6d12c3e8 100644
> --- a/arch/arm/boot/dts/bcm283x.dtsi
> +++ b/arch/arm/boot/dts/bcm283x.dtsi
> @@ -3,6 +3,8 @@
> #include <dt-bindings/clock/bcm2835-aux.h>
> #include <dt-bindings/gpio/gpio.h>
>
> +/memreserve/ 0x00000000 0x00001000;

Can you put a comment above this /memreserve entry here to remind about
what this is useful for?

Thanks!

> +
> /* This include file covers the common peripherals and configuration between
> * bcm2835 and bcm2836 implementations, leaving the CPU configuration to
> * bcm2835.dtsi and bcm2836.dtsi.
>


--
Florian

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