On 29 June 2016 at 18:45, Catalin Marinas <catalin.marinas@xxxxxxx> wrote:
> On Wed, Jun 29, 2016 at 02:51:28PM +0200, Ard Biesheuvel wrote:
>> + if (!PAGE_ALIGNED(md->phys_addr) ||
>> + !PAGE_ALIGNED(md->num_pages << EFI_PAGE_SHIFT)) {
>> + /*
>> + * If the end address of this region is not aligned to page
>> + * size, the mapping is rounded up, and may end up sharing a
>> + * page frame with the next UEFI memory region. If we create
>> + * a block entry now, we may need to split it again when mapping
>> + * the next region, and support for that is going to be removed
>> + * from the MMU routines. So avoid block mappings altogether in
>> + * that case.
>> + */
>> + allow_block_mappings = false;
>> + }
>
> How common is it for large areas to have unaligned start/end? I wonder
> whether it's worth implementing my approach to look ahead and explicitly
> check the overlap with the next section instead of disabling block
> mappings altogether for this region.
>
Very uncommon. Typically, only MMIO regions that represent NOR flash
are larger than a couple of pages. Taken from QEMU:
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