On Thu, Dec 08, 2022 at 12:18:07AM +0000, Sean Christopherson wrote:
[...]
Together, what about? The #ifdef is a bit gross, especially around "hi_start", but it's less duplicate code. And IMO, having things bundled in the same place makes it a lot easier for newbies (to arm64 or kernel coding in general) to understand what's going on and why arm64 is different.
I'd rather we not go this route. We really shouldn't make any attempt to de-dupe something that is inherently architecture specific.
For example:
- /*
* All architectures supports splitting the virtual address space into* a high and a low half. Populate both halves, except for arm64 which* currently uses only TTBR0_EL1 (arbitrary selftests "logic"), i.e.* only has a valid low half.*/- sparsebit_num_t nr_va_bits = (1ULL << (vm->va_bits - 1)) >> vm->page_shift;
This is still wrong for arm64. When we say the VA space is 48 bits, we really do mean that TTBR0 is able to address a full 48 bits. So this truncates the MSB for the addressing mode.
With the code living in the arm64 side of the shop, I can also tailor the comment to directly match the architecture to provide breadcrumbs tying it back to the Arm ARM.
-- Thanks, Oliver