On Fri, 12 Jun, at 06:01:44PM, Jonathan (Zhixiong) Zhang wrote:
> From: "Jonathan (Zhixiong) Zhang" <zjzhang@xxxxxxxxxxxxxx>
>
> x86 and ia64 implement efi_mem_attributes() differently. This
> function needs to be available for other arch (such as arm64)
> as well, such as for the purpose of ACPI/APEI.
>
> ia64 efi does not setup memmap variable and does not set
> EFI_MEMMAP flag, so it needs to have its unique implementation
> of efi_mem_attributes().
Something like the above paragraph...
> @@ -517,3 +517,21 @@ char * __init efi_md_typeattr_format(char *buf, size_t size,
> attr & EFI_MEMORY_UC ? "UC" : "");
> return buf;
> }
needs to go here, i.e. as documentation for efi_mem_atributes(). You
need to explain why this function is marked as __weak at the function
definition site.
> +u64 __weak efi_mem_attributes(unsigned long phys_addr)
> +{
> + efi_memory_desc_t *md;
> + void *p;
> +
> + if (!efi_enabled(EFI_MEMMAP))
> + return 0;
> +
> + for (p = memmap.map; p < memmap.map_end; p += memmap.desc_size) {
> + md = p;
> + if ((md->phys_addr <= phys_addr) &&
> + (phys_addr < (md->phys_addr +
> + (md->num_pages << EFI_PAGE_SHIFT))))
> + return md->attribute;
> + }
> + return 0;
> +}
because otherwise people are going to read this in the future and think,
"efi_mem_attribute() doesn't quite work how I want it to for my arch,
but it's __weak, so I'll override it"
which is absolutely not the practice we should be promoting.
How about something like this,
/*
* efi_mem_attributes - lookup memmap attributes for physical address
* @phys_addr: the physical address to lookup
*
* Search in the EFI memory map for the region covering
* @phys_addr. Returns the EFI memory attributes if the region
* was found in the memory map, 0 otherwise.
*
* Despite being marked __weak most architectures should *not*
* override this function. It is __weak solely for the benefit
* of ia64 which has a funky EFI memory map that doesn't work
* the same way as other architectures.
*/
--
Matt Fleming, Intel Open Source Technology Center
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