On Thu, Aug 25, 2016 at 06:17:09PM +0200, Ard Biesheuvel wrote:
> Currently, memory regions are only recorded in the memblock memory table
> if they have the EFI_MEMORY_WB memory type attribute set. In case the
> region is of a reserved type, it is also marked as MEMBLOCK_NOMAP, which
> will leave it out of the linear mapping.
>
> However, memory regions may legally have the EFI_MEMORY_WT or EFI_MEMORY_WC
> attributes set, and the EFI_MEMORY_WB cleared, in which case the region in
> question is obviously backed by normal memory, but is not recorded in the
> memblock memory table at all. Since it would be useful to be able to
> identify any UEFI reported memory region using memblock_is_memory(), it
> makes sense to add all memory to the memblock memory table, and simply mark
> it as MEMBLOCK_NOMAP if it lacks the EFI_MEMORY_WB attribute.
>
> While implementing this, let's refactor the code slightly to make it easier
> to understand: replace is_normal_ram() with is_memory(), and make it return
> true for each region that has any of the WB|WT|WC bits set. (This follows
> the AArch64 bindings in the UEFI spec, which state that those are the
> attributes that map to normal memory)
>
> Also, replace is_reserve_region() with is_usable_memory(), and only invoke
> it if the region in question was identified as memory by is_memory() in the
> first place. The net result is the same (only reserved regions that are
> backed by memory end up in the memblock memory table with the MEMBLOCK_NOMAP
> flag set) but carried out in a more straightforward way.
>
> Finally, we remove the trailing asterisk in the EFI debug output. Keeping it
> clutters the code, and it serves no real purpose now that we no longer
> temporarily reserve BootServices code and data regions like we did in the
> early days of EFI support on arm64 Linux (which it inherited from the x86
> implementation)
>
> Signed-off-by: Ard Biesheuvel <ard.biesheuvel@xxxxxxxxxx>
Reviewed-by: Leif Lindholm <leif.lindholm@xxxxxxxxxx>
> ---
> v2: refactor is_normal_ram and is_reserve_region
> drop trailing asterisk in EFI debug output
>
> drivers/firmware/efi/arm-init.c | 32 +++++++++++---------
> 1 file changed, 17 insertions(+), 15 deletions(-)
>
> diff --git a/drivers/firmware/efi/arm-init.c b/drivers/firmware/efi/arm-init.c
> index c49d50e68aee..c2ac5975fd5d 100644
> --- a/drivers/firmware/efi/arm-init.c
> +++ b/drivers/firmware/efi/arm-init.c
> @@ -26,9 +26,9 @@
>
> u64 efi_system_table;
>
> -static int __init is_normal_ram(efi_memory_desc_t *md)
> +static int __init is_memory(efi_memory_desc_t *md)
> {
> - if (md->attribute & EFI_MEMORY_WB)
> + if (md->attribute & (EFI_MEMORY_WB|EFI_MEMORY_WT|EFI_MEMORY_WC))
> return 1;
> return 0;
> }
> @@ -152,9 +152,9 @@ out:
> }
>
> /*
> - * Return true for RAM regions we want to permanently reserve.
> + * Return true for regions that can be used as System RAM.
> */
> -static __init int is_reserve_region(efi_memory_desc_t *md)
> +static __init int is_usable_memory(efi_memory_desc_t *md)
> {
> switch (md->type) {
> case EFI_LOADER_CODE:
> @@ -163,18 +163,22 @@ static __init int is_reserve_region(efi_memory_desc_t *md)
> case EFI_BOOT_SERVICES_DATA:
> case EFI_CONVENTIONAL_MEMORY:
> case EFI_PERSISTENT_MEMORY:
> - return 0;
> + /*
> + * According to the spec, these regions are no longer reserved
> + * after calling ExitBootServices(). However, we can only use
> + * them as System RAM if they can be mapped writeback cacheable.
> + */
> + return (md->attribute & EFI_MEMORY_WB);
> default:
> break;
> }
> - return is_normal_ram(md);
> + return false;
> }
>
> static __init void reserve_regions(void)
> {
> efi_memory_desc_t *md;
> u64 paddr, npages, size;
> - int resv;
>
> if (efi_enabled(EFI_DBG))
> pr_info("Processing EFI memory map:\n");
> @@ -191,25 +195,23 @@ static __init void reserve_regions(void)
> paddr = md->phys_addr;
> npages = md->num_pages;
>
> - resv = is_reserve_region(md);
> if (efi_enabled(EFI_DBG)) {
> char buf[64];
>
> - pr_info(" 0x%012llx-0x%012llx %s%s\n",
> + pr_info(" 0x%012llx-0x%012llx %s\n",
> paddr, paddr + (npages << EFI_PAGE_SHIFT) - 1,
> - efi_md_typeattr_format(buf, sizeof(buf), md),
> - resv ? "*" : "");
> + efi_md_typeattr_format(buf, sizeof(buf), md));
> }
>
> memrange_efi_to_native(&paddr, &npages);
> size = npages << PAGE_SHIFT;
>
> - if (is_normal_ram(md))
> + if (is_memory(md)) {
> early_init_dt_add_memory_arch(paddr, size);
>
> - if (resv)
> - memblock_mark_nomap(paddr, size);
> -
> + if (!is_usable_memory(md))
> + memblock_mark_nomap(paddr, size);
> + }
> }
>
> set_bit(EFI_MEMMAP, &efi.flags);
> --
> 2.7.4
>
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