On 08/29/2018 08:45 AM, 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 4.19-rc1.

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

This is great stuff. I'm hoping to catch up at Connect and discuss.

Help me understand something. Without the kernel side of this patch, and
the increase in linear map for installed RAM, what upside do I see other
than being able to allocate from a higher VA space?

Jon.

-- 
Computer Architect | Sent from my Fedora powered laptop