On Thu, Dec 06, 2018 at 10:50:35PM +0000, Steve Capper wrote:

This patch series brings support for 52-bit userspace VAs to systems that
have ARMv8.2-LVA and are running with a 48-bit VA_BITS and a 64KB
PAGE_SIZE.

If no hardware support is present, the kernel runs with a 48-bit VA space
for userspace.

Userspace can exploit this feature by providing an address hint to mmap
where addr[51:48] != 0. Otherwise all the VA mappings will behave in the
same way as a 48-bit VA system (this is to maintain compatibility with
software that assumes the maximum VA size on arm64 is 48-bit).

This patch series applies to 4.20-rc1.

Testing was in a model with Trusted Firmware and UEFI for boot.

Changed in V5, ttbr1 offsetting code simplified. Extra patch added to
check for VA space support mismatch between CPUs.

I was all ready to push this out, but I spotted a build failure with
allmodconfig because TASK_SIZE refers to the non-EXPORTed symbol
vabits_user:

ERROR: "vabits_user" [lib/test_user_copy.ko] undefined!
ERROR: "vabits_user" [drivers/misc/lkdtm/lkdtm.ko] undefined!
ERROR: "vabits_user" [drivers/infiniband/hw/mlx5/mlx5_ib.ko] undefined!

So I've pushed an extra patch on top to fix that by exporting the symbol.

Will

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