[PATCH master] ARM: mmu: increase early page table size to 256K for now

[PATCH master] ARM: mmu: increase early page table size to 256K for now

[Ahmad Fatoum]

With recent changes for W^X, the size of our early page tables have grown
in some cases, so they no longer fit into the 64K we reserve for them.

This has been observed in at least two ARM64 platforms:

  - i.MX8M with OP-TEE at start of RAM (on master)
  - Raspberry Pi Zero 2 without OP-TEE (on next)

It's very likely we are overly wasteful of space, but until that's fixed
properly, increase the size reserved for our early page tables.

Signed-off-by: Ahmad Fatoum <a.fatoum@barebox.org>
---
 arch/arm/include/asm/barebox-arm.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/arm/include/asm/barebox-arm.h b/arch/arm/include/asm/barebox-arm.h
index da6f5d528338..11be8b85837e 100644
--- a/arch/arm/include/asm/barebox-arm.h
+++ b/arch/arm/include/asm/barebox-arm.h
@@ -26,7 +26,7 @@
 #include <linux/stringify.h>
 #include <pbl/handoff-data.h>
 
-#define ARM_EARLY_PAGETABLE_SIZE	SZ_64K
+#define ARM_EARLY_PAGETABLE_SIZE	SZ_256K
 
 #define handoff_add_arm_machine(machine)				\
 	do {								\
-- 
2.39.5

Re: [PATCH master] ARM: mmu: increase early page table size to 256K for now

[Marco Felsch]

Hi Ahmad,

On 25-08-22, Ahmad Fatoum wrote:
> With recent changes for W^X, the size of our early page tables have grown
> in some cases, so they no longer fit into the 64K we reserve for them.
> 
> This has been observed in at least two ARM64 platforms:
> 
>   - i.MX8M with OP-TEE at start of RAM (on master)
>   - Raspberry Pi Zero 2 without OP-TEE (on next)
> 
> It's very likely we are overly wasteful of space, but until that's fixed
> properly, increase the size reserved for our early page tables.

shall we add a TODO within the code?

> Signed-off-by: Ahmad Fatoum <a.fatoum@barebox.org>

Reviewed-by: Marco Felsch <m.felsch@pengutronix.de>

Regards,
  Marco


> ---
>  arch/arm/include/asm/barebox-arm.h | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/arch/arm/include/asm/barebox-arm.h b/arch/arm/include/asm/barebox-arm.h
> index da6f5d528338..11be8b85837e 100644
> --- a/arch/arm/include/asm/barebox-arm.h
> +++ b/arch/arm/include/asm/barebox-arm.h
> @@ -26,7 +26,7 @@
>  #include <linux/stringify.h>
>  #include <pbl/handoff-data.h>
>  
> -#define ARM_EARLY_PAGETABLE_SIZE	SZ_64K
> +#define ARM_EARLY_PAGETABLE_SIZE	SZ_256K
>  
>  #define handoff_add_arm_machine(machine)				\
>  	do {								\
> -- 
> 2.39.5
> 
>