Re: [PATCH 1/2 v5] arm64: Get rid of __early_init_dt_declare_initrd()

[Rob Herring <robh+dt@kernel.org>]

+Ard who last touched this.

On Mon, Oct 29, 2018 at 2:23 PM Florian Fainelli <f.fainelli@gmail.com> wrote:
>
> ARM64 is the only architecture that re-defines
> __early_init_dt_declare_initrd() in order for that function to populate
> initrd_start/initrd_end with physical addresses instead of virtual
> addresses. Instead of having an override, just get rid of that
> implementation and perform the virtual to physical conversion of these
> addresses in arm64_memblock_init() where relevant.
>
> Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>
> Signed-off-by: Mike Rapoport <rppt@linux.ibm.com>
> ---
>  arch/arm64/include/asm/memory.h |  8 -------
>  arch/arm64/mm/init.c            | 42 +++++++++++++++++++++------------
>  2 files changed, 27 insertions(+), 23 deletions(-)
>
> diff --git a/arch/arm64/include/asm/memory.h b/arch/arm64/include/asm/memory.h
> index b96442960aea..dc3ca21ba240 100644
> --- a/arch/arm64/include/asm/memory.h
> +++ b/arch/arm64/include/asm/memory.h
> @@ -168,14 +168,6 @@
>  #define IOREMAP_MAX_ORDER      (PMD_SHIFT)
>  #endif
>
> -#ifdef CONFIG_BLK_DEV_INITRD
> -#define __early_init_dt_declare_initrd(__start, __end)                 \
> -       do {                                                            \
> -               initrd_start = (__start);                               \
> -               initrd_end = (__end);                                   \
> -       } while (0)
> -#endif
> -
>  #ifndef __ASSEMBLY__
>
>  #include <linux/bitops.h>
> diff --git a/arch/arm64/mm/init.c b/arch/arm64/mm/init.c
> index 3cf87341859f..292570b08f85 100644
> --- a/arch/arm64/mm/init.c
> +++ b/arch/arm64/mm/init.c
> @@ -62,6 +62,8 @@
>  s64 memstart_addr __ro_after_init = -1;
>  phys_addr_t arm64_dma_phys_limit __ro_after_init;
>
> +static phys_addr_t phys_initrd_start, phys_initrd_end;
> +
>  #ifdef CONFIG_BLK_DEV_INITRD
>  static int __init early_initrd(char *p)
>  {
> @@ -72,8 +74,8 @@ static int __init early_initrd(char *p)
>         if (*endp == ',') {
>                 size = memparse(endp + 1, NULL);
>
> -               initrd_start = start;
> -               initrd_end = start + size;
> +               phys_initrd_start = start;
> +               phys_initrd_end = start + size;
>         }
>         return 0;
>  }
> @@ -364,6 +366,7 @@ static void __init fdt_enforce_memory_region(void)
>  void __init arm64_memblock_init(void)
>  {
>         const s64 linear_region_size = -(s64)PAGE_OFFSET;
> +       u64 __maybe_unused base, size;
>
>         /* Handle linux,usable-memory-range property */
>         fdt_enforce_memory_region();
> @@ -408,14 +411,25 @@ void __init arm64_memblock_init(void)
>                 memblock_add(__pa_symbol(_text), (u64)(_end - _text));
>         }
>
> -       if (IS_ENABLED(CONFIG_BLK_DEV_INITRD) && initrd_start) {
> +       if (IS_ENABLED(CONFIG_BLK_DEV_INITRD) &&
> +           (initrd_start || phys_initrd_start)) {

I've tried to explain already that this is broken. The problem is
__early_init_dt_declare_initrd using __va() which happens before this
function is called. __va() uses PHYS_OFFSET which in turn is defined
as memstart_addr. However, memstart_addr may be changed just above
this hunk, so the earlier conversion to a VA may not be valid at this
point. This is explained if you read Ard's commit that added all this
mess.

You could fix this by converting back to a PA before adjusting
memstart_addr, but that's 2 wrongs making a right and fragile. The
better solution is the other proposal making the DT code set
phys_initrd_* (whatever the ARM code calls them).

>                 /*
>                  * Add back the memory we just removed if it results in the
>                  * initrd to become inaccessible via the linear mapping.
>                  * Otherwise, this is a no-op
>                  */
> -               u64 base = initrd_start & PAGE_MASK;
> -               u64 size = PAGE_ALIGN(initrd_end) - base;
> +               if (phys_initrd_start) {
> +                       /* Command line specified the initrd location */
> +                       initrd_start = __phys_to_virt(phys_initrd_start);
> +                       initrd_end = __phys_to_virt(phys_initrd_end);
> +               } else if (initrd_start) {
> +                       /* FDT specified the initrd location */
> +                       phys_initrd_start = __pa(initrd_start);
> +                       phys_initrd_end = __pa(initrd_end);

Kind of inconsistent to mix __phys_to_virt and __pa flavors.

Rob