On Tue, 22 Sep 2020, Ard Biesheuvel wrote:

By changing the patchable sequences and the patching logic to carry
more bits of offset, we can improve this: 11 bits gives us 4 GiB >> 11
== 2 MiB granularity, and so you never waste more than that amount by
rounding up the physical start of DRAM to the next multiple of 2 MiB.
(Note that 2 MiB granularity guarantees that the linear mapping can be
created efficiently, whereas less than 2 MiB may result in the linear
mapping needing another level of page tables)

That is IMHO the top argument for limiting it to 2 MiB.
It would be worth making this explicit in the commit log.


Nicolas

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