On 4 September 2015 at 20:23, Matt Fleming <matt@xxxxxxxxxxxxxxxxxxx> wrote: > On Fri, 04 Sep, at 03:24:21PM, Ard Biesheuvel wrote: >> >> Since the UEFI spec does not mandate an enumeration order for >> GetMemoryMap(), it seems to me that you still need to sort its output >> before laying out the VA space. Since you need to sort it anyway, why >> not simply sort it in reverse order and keep all the original code? >> Considering that this is meant for stable, that would keep the delta >> *much* smaller. > > Hmm... that'd be a neat trick and while it would save on the diff > size, I don't think it would be smaller in terms of change complexity. > > EDK2 sorts the memory map when EFI_PROPERTIES_TABLE is enabled, so we > can be reasonably sure the entry order returned by GetMemoryMap() is > compatible with the split regions, even if it's not mandated by the > spec. > EDK2 does sort it, but the spec does not mandate it so another implementation may do something different entirely. > For the non-EFI_PROPERTIES_TABLE case, things have been working fine > without the sorting, so I'm reluctant to introduce it now (it's also > much less of an issue there). > I see. I do wonder, since the VA mapping preserves the modulo 2 MB alignment of each region, aren't you using much more VA space when mapping in reverse order as you are doing now? -- Ard. -- To unsubscribe from this list: send the line "unsubscribe linux-efi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
