mbox series

[0/5] 52-bit userspace VAs

Message ID 20180829124543.25314-1-steve.capper@arm.com (mailing list archive)
Headers show
Series 52-bit userspace VAs | expand

Message

Steve Capper Aug. 29, 2018, 12:45 p.m. UTC 
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.

Steve Capper (5):
  arm64: mm: Introduce DEFAULT_MAP_WINDOW
  arm64: mm: introduce 52-bit userspace support
  arm64: mm: Copy over arch_get_unmapped_area
  arm64: mmap: Allow for "high" 52-bit VA allocations
  arm64: mm: Activate 52-bit userspace VA support

 arch/arm64/Kconfig                      |  4 ++
 arch/arm64/include/asm/assembler.h      |  7 +--
 arch/arm64/include/asm/cpucaps.h        |  3 +-
 arch/arm64/include/asm/elf.h            |  2 +-
 arch/arm64/include/asm/mmu_context.h    |  3 +
 arch/arm64/include/asm/pgalloc.h        |  4 ++
 arch/arm64/include/asm/pgtable.h        | 23 +++++++-
 arch/arm64/include/asm/processor.h      | 19 ++++---
 arch/arm64/kernel/cpufeature.c          | 16 ++++++
 arch/arm64/kernel/entry.S               |  6 +-
 arch/arm64/kernel/head.S                | 13 +++++
 arch/arm64/mm/fault.c                   |  2 +-
 arch/arm64/mm/mmap.c                    | 98 +++++++++++++++++++++++++++++++++
 arch/arm64/mm/mmu.c                     |  1 +
 arch/arm64/mm/proc.S                    | 10 +++-
 drivers/firmware/efi/arm-runtime.c      |  2 +-
 drivers/firmware/efi/libstub/arm-stub.c |  2 +-
 17 files changed, 194 insertions(+), 21 deletions(-)

Comments

Jon Masters Sept. 7, 2018, 6:22 a.m. UTC | #1 
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.
Steve Capper Sept. 7, 2018, 1:59 p.m. UTC | #2 
On Fri, Sep 07, 2018 at 02:22:49AM -0400, Jon Masters wrote:
> 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?
>

Hi Jon,
The main benefit from this series is that it allows for 52-bit VA
testing to take place in userspace on smaller systems.

Cheers,