On 31.05.23 12:35, Sascha Hauer wrote:
> We used to skip setting the zero page to faulting when SDRAM starts
> at 0x0. As bootm code now explicitly sets the zero page accessible
> before copying ATAGs there this should no longer be necessary, so
> unconditionally set the zero page to faulting during MMU startup.
> This also moves the zero page setup after the point the SDRAM has
> been mapped cachable, because otherwise the zero page setup would
> be overwritten.
>
> Signed-off-by: Sascha Hauer <s.hauer@xxxxxxxxxxxxxx>
> ---
> arch/arm/cpu/mmu_32.c | 26 +++++++-------------------
> 1 file changed, 7 insertions(+), 19 deletions(-)
>
> diff --git a/arch/arm/cpu/mmu_32.c b/arch/arm/cpu/mmu_32.c
> index c4e5a3bb0a..fdbc0293a3 100644
> --- a/arch/arm/cpu/mmu_32.c
> +++ b/arch/arm/cpu/mmu_32.c
> @@ -459,23 +459,6 @@ static int set_vector_table(unsigned long adr)
> return -EINVAL;
> }
>
> -static void create_zero_page(void)
> -{
> - struct resource *zero_sdram;
> -
> - zero_sdram = request_sdram_region("zero page", 0x0, PAGE_SIZE);
> - if (zero_sdram) {
> - /*
> - * Here we would need to set the second level page table
> - * entry to faulting. This is not yet implemented.
> - */
> - pr_debug("zero page is in SDRAM area, currently not supported\n");
> - } else {
> - zero_page_faulting();
> - pr_debug("Created zero page\n");
> - }
> -}
> -
> /*
> * Map vectors and zero page
> */
> @@ -487,7 +470,6 @@ static void vectors_init(void)
> */
> if (!set_vector_table((unsigned long)__exceptions_start)) {
> arm_fixup_vectors();
> - create_zero_page();
> return;
> }
>
> @@ -495,7 +477,6 @@ static void vectors_init(void)
> * Next try high vectors at 0xffff0000.
> */
> if (!set_vector_table(ARM_HIGH_VECTORS)) {
> - create_zero_page();
> create_vector_table(ARM_HIGH_VECTORS);
> return;
> }
> @@ -552,6 +533,13 @@ void __mmu_init(bool mmu_on)
>
> remap_range((void *)pos, bank->start + bank->size - pos, MAP_CACHED);
> }
> +
> + /*
> + * In case the zero page is in SDRAM request it to prevent others
> + * from using it
> + */
> + request_sdram_region("zero page", 0x0, PAGE_SIZE);
> + zero_page_faulting();
I think this would break the case of having low vectors (at address 0).
We have vector_table requested if that's the case, so we need to check:
if (!zero_page_in_sdram() || !zero_page_already_sdram_requested())
zero_page_faulting();
Cheers,
Ahmad
> }
>
> /*
--
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