Re: [Xen-devel] [PATCH MM-PART2 RESEND v2 17/19] xen/arm: mm: Initialize page-tables earlier

[Stefano Stabellini <sstabellini@xxxxxxxxxx>]

On Tue, 14 May 2019, Julien Grall wrote:
> Since commit f60658c6ae "xen/arm: Stop relocating Xen", the function
> setup_page_tables() does not require any information from the FDT.
> 
> So the initialization of the page-tables can be done much earlier in the
> boot process. The earliest setup_page_tables() can be called is after
> traps have been initialized, so we can get backtrace if an error
> occurred.
> 
> Moving the initialization of the page-tables also avoid the dance to map
> the FDT again in the new set of page-tables.
> 
> Signed-off-by: Julien Grall <julien.grall@xxxxxxx>
> Reviewed-by: Andrii Anisov <andrii_anisov@xxxxxxxx>
> 
> ---
>     Changes in v2:
>         - Add Andrii's reviewed-by
> ---
>  xen/arch/arm/mm.c    | 12 +++---------
>  xen/arch/arm/setup.c |  4 ++--
>  2 files changed, 5 insertions(+), 11 deletions(-)
> 
> diff --git a/xen/arch/arm/mm.c b/xen/arch/arm/mm.c
> index 7502a14760..eacc1647e0 100644
> --- a/xen/arch/arm/mm.c
> +++ b/xen/arch/arm/mm.c
> @@ -550,7 +550,7 @@ static inline lpae_t pte_of_xenaddr(vaddr_t va)
>      return mfn_to_xen_entry(maddr_to_mfn(ma), MT_NORMAL);
>  }
>  
> -/* Map the FDT in the early boot page table */
> +/* Map the FDT in the runtime page table */

I think you can drop this comment now.

In any case:

Reviewed-by: Stefano Stabellini <sstabellini@xxxxxxxxxx>


>  void * __init early_fdt_map(paddr_t fdt_paddr)
>  {
>      /* We are using 2MB superpage for mapping the FDT */
> @@ -573,7 +573,7 @@ void * __init early_fdt_map(paddr_t fdt_paddr)
>      /* The FDT is mapped using 2MB superpage */
>      BUILD_BUG_ON(BOOT_FDT_VIRT_START % SZ_2M);
>  
> -    create_mappings(boot_second, BOOT_FDT_VIRT_START, 
> paddr_to_pfn(base_paddr),
> +    create_mappings(xen_second, BOOT_FDT_VIRT_START, 
> paddr_to_pfn(base_paddr),
>                      SZ_2M >> PAGE_SHIFT, SZ_2M);
>  
>      offset = fdt_paddr % SECOND_SIZE;
> @@ -588,7 +588,7 @@ void * __init early_fdt_map(paddr_t fdt_paddr)
>  
>      if ( (offset + size) > SZ_2M )
>      {
> -        create_mappings(boot_second, BOOT_FDT_VIRT_START + SZ_2M,
> +        create_mappings(xen_second, BOOT_FDT_VIRT_START + SZ_2M,
>                          paddr_to_pfn(base_paddr + SZ_2M),
>                          SZ_2M >> PAGE_SHIFT, SZ_2M);
>      }
> @@ -699,12 +699,6 @@ void __init setup_pagetables(unsigned long 
> boot_phys_offset)
>      pte.pt.table = 1;
>      xen_second[second_table_offset(FIXMAP_ADDR(0))] = pte;
>  
> -    /* ... DTB */
> -    pte = boot_second[second_table_offset(BOOT_FDT_VIRT_START)];
> -    xen_second[second_table_offset(BOOT_FDT_VIRT_START)] = pte;
> -    pte = boot_second[second_table_offset(BOOT_FDT_VIRT_START + SZ_2M)];
> -    xen_second[second_table_offset(BOOT_FDT_VIRT_START + SZ_2M)] = pte;
> -
>  #ifdef CONFIG_ARM_64
>      ttbr = (uintptr_t) xen_pgtable + phys_offset;
>  #else
> diff --git a/xen/arch/arm/setup.c b/xen/arch/arm/setup.c
> index 2f714d8b37..889da40d8d 100644
> --- a/xen/arch/arm/setup.c
> +++ b/xen/arch/arm/setup.c
> @@ -759,6 +759,8 @@ void __init start_xen(unsigned long boot_phys_offset,
>      /* Initialize traps early allow us to get backtrace when an error 
> occurred */
>      init_traps();
>  
> +    setup_pagetables(boot_phys_offset);
> +
>      smp_clear_cpu_maps();
>  
>      device_tree_flattened = early_fdt_map(fdt_paddr);
> @@ -780,8 +782,6 @@ void __init start_xen(unsigned long boot_phys_offset,
>                               (paddr_t)(uintptr_t)(_end - _start + 1), false);
>      BUG_ON(!xen_bootmodule);
>  
> -    setup_pagetables(boot_phys_offset);
> -
>      setup_mm(fdt_paddr, fdt_size);
>  
>      /* Parse the ACPI tables for possible boot-time configuration */
> -- 
> 2.11.0
> 

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