[v3,00/60] arm64: Add support for LPA2 at stage1 and WXN

  This is a followup to [0], which was a lot smaller. Thanks to Ryan for
feedback and review. This series is independent from Ryan's work on
adding support for LPA2 to KVM - the only potential source of conflict
should be the patch "arm64: kvm: Limit HYP VA and host S2 range to 48
bits when LPA2 is in effect", which could simply be dropped in favour of
the KVM changes to make it support LPA2.

The first ~15 patches of this series rework how the kernel VA space is
organized, so that the vmemmap region does not take up more space than
necessary, and so that most of it can be reclaimed when running a build
capable of 52-bit virtual addressing on hardware that is not. This is
needed because the vmemmap region will take up a substantial part of the
upper VA region that it shares with the kernel, modules and
vmalloc/vmap mappings once we enable LPA2 with 4k pages.

The next ~30 patches rework the early init code, reimplementing most of
the page table and relocation handling in C code. There are several
reasons why this is beneficial:
- we generally prefer C code over asm for these things, and the macros
  that currently exist in head.S for creating the kernel pages tables
  are a good example why;
- we no longer need to create the kernel mapping in two passes, which
  means we can remove the logic that copies parts of the fixmap and the
  KAsan shadow from one set of page tables to the other; this is
  especially advantageous for KAsan with LPA2, which needs more
  elaborate shadow handling across multiple levels, since the KAsan
  region cannot be placed on exact pgd_t bouundaries in that case;
- we can read the ID registers and parse command line overrides before
  creating the page tables, which simplifies the LPA2 case, as flicking
  the global TCR_EL1.DS bit at a later stage would require elaborate
  repainting of all page table descriptors, some of which with the MMU
  disabled;
- we can use more elaborate logic to create the mappings, which means we
  can use more precise mappings for code and data sections even when
  using 2 MiB granularity, and this is a prerequisite for running with
  WXN.

As part of the ID map changes, we decouple the ID map size from the
kernel VA size, and switch to a 48-bit VA map for all configurations.

The next 18 patches rework the existing LVA support as a CPU feature,
which simplifies some code and gets rid of the vabits_actual variable.
Then, LPA2 support is implemented in the same vein. This requires adding
support for 5 level paging as well, given that LPA2 introduces a new
paging level '-1' when using 4k pages.

Combined with the vmemmap changes at the start of the series, the
resulting LPA2/4k pages configuration will have the exact same VA space
layout as the ordinary 4k/4 levels configuration, and so LPA2 support
can reasonably be enabled by default, as the fallback is seamless on
non-LPA2 hardware.

In the 16k/LPA2 case, the fallback also reduces the number of paging
levels, resulting in a 47-bit VA space. This is based on the assumption
that hybrid LPA2/non-LPA2 16k pages kernels in production use would
prefer not to take the performance hit of 4 level paging to gain only a
single additional bit of VA space. (Note that generic Android kernels
use only 3 levels of paging today.) Bespoke 16k configurations can still
configure 48-bit virtual addressing as before.

Finally, the last two patches enable support for running with the WXN
control enabled. This was previously part of a separate series [1], but
given that the delta is tiny, it is included here as well.

[0] https://lore.kernel.org/all/20221124123932.2648991-1-ardb@kernel.org/
[1] https://lore.kernel.org/all/20221111171201.2088501-1-ardb@kernel.org/

Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Will Deacon <will@kernel.org>
Cc: Marc Zyngier <maz@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Ryan Roberts <ryan.roberts@arm.com>
Cc: Anshuman Khandual <anshuman.khandual@arm.com>
Cc: Kees Cook <keescook@chromium.org>

Anshuman Khandual (2):
  arm64/mm: Add FEAT_LPA2 specific TCR_EL1.DS field
  arm64/mm: Add FEAT_LPA2 specific ID_AA64MMFR0.TGRAN[2]

Ard Biesheuvel (57):

  // KASLR / vmemmap reorg
  arm64: kernel: Disable latent_entropy GCC plugin in early C runtime
  arm64: mm: Take potential load offset into account when KASLR is off
  arm64: mm: get rid of kimage_vaddr global variable
  arm64: mm: Move PCI I/O emulation region above the vmemmap region
  arm64: mm: Move fixmap region above vmemmap region
  arm64: ptdump: Allow VMALLOC_END to be defined at boot
  arm64: ptdump: Discover start of vmemmap region at runtime
  arm64: vmemmap: Avoid base2 order of struct page size to dimension
    region
  arm64: mm: Reclaim unused vmemmap region for vmalloc use
  arm64: kaslr: Adjust randomization range dynamically
  arm64: kaslr: drop special case for ThunderX in kaslr_requires_kpti()
  arm64: kvm: honour 'nokaslr' command line option for the HYP VA space

  // Reimplement page table creation code in C
  arm64: kernel: Manage absolute relocations in code built under pi/
  arm64: kernel: Don't rely on objcopy to make code under pi/ __init
  arm64: head: move relocation handling to C code
  arm64: idreg-override: Omit non-NULL checks for override pointer
  arm64: idreg-override: Prepare for place relative reloc patching
  arm64: idreg-override: Avoid parameq() and parameqn()
  arm64: idreg-override: avoid strlen() to check for empty strings
  arm64: idreg-override: Avoid sprintf() for simple string concatenation
  arm64: idreg-override: Avoid kstrtou64() to parse a single hex digit
  arm64: idreg-override: Move to early mini C runtime
  arm64: kernel: Remove early fdt remap code
  arm64: head: Clear BSS and the kernel page tables in one go
  arm64: Move feature overrides into the BSS section
  arm64: head: Run feature override detection before mapping the kernel
  arm64: head: move dynamic shadow call stack patching into early C
    runtime
  arm64: kaslr: Use feature override instead of parsing the cmdline
    again
  arm64: idreg-override: Create a pseudo feature for rodata=off
  arm64: Add helpers to probe local CPU for PAC/BTI/E0PD support
  arm64: head: allocate more pages for the kernel mapping
  arm64: head: move memstart_offset_seed handling to C code
  arm64: head: Move early kernel mapping routines into C code
  arm64: mm: Use 48-bit virtual addressing for the permanent ID map
  arm64: pgtable: Decouple PGDIR size macros from PGD/PUD/PMD levels
  arm64: kernel: Create initial ID map from C code
  arm64: mm: avoid fixmap for early swapper_pg_dir updates
  arm64: mm: omit redundant remap of kernel image
  arm64: Revert "mm: provide idmap pointer to cpu_replace_ttbr1()"

  // Implement LPA2 support
  arm64: mm: Handle LVA support as a CPU feature
  arm64: mm: Add feature override support for LVA
  arm64: mm: Wire up TCR.DS bit to PTE shareability fields
  arm64: mm: Add LPA2 support to phys<->pte conversion routines
  arm64: mm: Add definitions to support 5 levels of paging
  arm64: mm: add LPA2 and 5 level paging support to G-to-nG conversion
  arm64: Enable LPA2 at boot if supported by the system
  arm64: mm: Add 5 level paging support to fixmap and swapper handling
  arm64: kasan: Reduce minimum shadow alignment and enable 5 level
    paging
  arm64: mm: Add support for folding PUDs at runtime
  arm64: ptdump: Disregard unaddressable VA space
  arm64: ptdump: Deal with translation levels folded at runtime
  arm64: kvm: avoid CONFIG_PGTABLE_LEVELS for runtime levels
  arm64: kvm: Limit HYP VA and host S2 range to 48 bits when LPA2 is in
    effect
  arm64: Enable 52-bit virtual addressing for 4k and 16k granule configs
  arm64: defconfig: Enable LPA2 support

  // Allow WXN control to be enabled at boot
  mm: add arch hook to validate mmap() prot flags
  arm64: mm: add support for WXN memory translation attribute

Marc Zyngier (1):
  arm64: Turn kaslr_feature_override into a generic SW feature override

 arch/arm64/Kconfig                      |  34 +-
 arch/arm64/configs/defconfig            |   2 +-
 arch/arm64/include/asm/assembler.h      |  55 +--
 arch/arm64/include/asm/cpufeature.h     | 102 +++++
 arch/arm64/include/asm/fixmap.h         |   1 +
 arch/arm64/include/asm/kasan.h          |   2 -
 arch/arm64/include/asm/kernel-pgtable.h | 104 ++---
 arch/arm64/include/asm/memory.h         |  50 +--
 arch/arm64/include/asm/mman.h           |  36 ++
 arch/arm64/include/asm/mmu.h            |  26 +-
 arch/arm64/include/asm/mmu_context.h    |  49 ++-
 arch/arm64/include/asm/pgalloc.h        |  53 ++-
 arch/arm64/include/asm/pgtable-hwdef.h  |  33 +-
 arch/arm64/include/asm/pgtable-prot.h   |  18 +-
 arch/arm64/include/asm/pgtable-types.h  |   6 +
 arch/arm64/include/asm/pgtable.h        | 229 +++++++++-
 arch/arm64/include/asm/scs.h            |  34 +-
 arch/arm64/include/asm/setup.h          |   3 -
 arch/arm64/include/asm/sysreg.h         |   2 +
 arch/arm64/include/asm/tlb.h            |   3 +-
 arch/arm64/kernel/Makefile              |   7 +-
 arch/arm64/kernel/cpu_errata.c          |   2 +-
 arch/arm64/kernel/cpufeature.c          |  90 ++--
 arch/arm64/kernel/head.S                | 465 ++------------------
 arch/arm64/kernel/idreg-override.c      | 322 --------------
 arch/arm64/kernel/image-vars.h          |  32 ++
 arch/arm64/kernel/kaslr.c               |   4 +-
 arch/arm64/kernel/module.c              |   2 +-
 arch/arm64/kernel/pi/Makefile           |  28 +-
 arch/arm64/kernel/pi/idreg-override.c   | 396 +++++++++++++++++
 arch/arm64/kernel/pi/kaslr_early.c      |  78 +---
 arch/arm64/kernel/pi/map_kernel.c       | 284 ++++++++++++
 arch/arm64/kernel/pi/map_range.c        | 104 +++++
 arch/arm64/kernel/{ => pi}/patch-scs.c  |  36 +-
 arch/arm64/kernel/pi/pi.h               |  30 ++
 arch/arm64/kernel/pi/relacheck.c        | 130 ++++++
 arch/arm64/kernel/pi/relocate.c         |  64 +++
 arch/arm64/kernel/setup.c               |  22 -
 arch/arm64/kernel/sleep.S               |   3 -
 arch/arm64/kernel/suspend.c             |   2 +-
 arch/arm64/kernel/vmlinux.lds.S         |  14 +-
 arch/arm64/kvm/hyp/nvhe/mem_protect.c   |   2 +
 arch/arm64/kvm/mmu.c                    |  22 +-
 arch/arm64/kvm/va_layout.c              |  10 +-
 arch/arm64/mm/init.c                    |   2 +-
 arch/arm64/mm/kasan_init.c              | 154 +++++--
 arch/arm64/mm/mmap.c                    |   4 +
 arch/arm64/mm/mmu.c                     | 268 ++++++-----
 arch/arm64/mm/pgd.c                     |  17 +-
 arch/arm64/mm/proc.S                    | 106 ++++-
 arch/arm64/mm/ptdump.c                  |  43 +-
 arch/arm64/tools/cpucaps                |   1 +
 include/linux/mman.h                    |  15 +
 mm/mmap.c                               |   3 +
 54 files changed, 2259 insertions(+), 1345 deletions(-)
 delete mode 100644 arch/arm64/kernel/idreg-override.c
 create mode 100644 arch/arm64/kernel/pi/idreg-override.c
 create mode 100644 arch/arm64/kernel/pi/map_kernel.c
 create mode 100644 arch/arm64/kernel/pi/map_range.c
 rename arch/arm64/kernel/{ => pi}/patch-scs.c (89%)
 create mode 100644 arch/arm64/kernel/pi/pi.h
 create mode 100644 arch/arm64/kernel/pi/relacheck.c
 create mode 100644 arch/arm64/kernel/pi/relocate.c
  

Hi Ard,

Just to say that I plan to work my way through this lot over the next couple of
weeks. I hope you can tolerate comments dribbling in as I go?

I'll also try integrating this with my latest revision for the KVM side of
things and re-run all my tests. I'll report back in due course.

Thanks,
Ryan


On 07/03/2023 14:04, Ard Biesheuvel wrote:
> This is a followup to [0], which was a lot smaller. Thanks to Ryan for
> feedback and review. This series is independent from Ryan's work on
> adding support for LPA2 to KVM - the only potential source of conflict
> should be the patch "arm64: kvm: Limit HYP VA and host S2 range to 48
> bits when LPA2 is in effect", which could simply be dropped in favour of
> the KVM changes to make it support LPA2.
> 
> The first ~15 patches of this series rework how the kernel VA space is
> organized, so that the vmemmap region does not take up more space than
> necessary, and so that most of it can be reclaimed when running a build
> capable of 52-bit virtual addressing on hardware that is not. This is
> needed because the vmemmap region will take up a substantial part of the
> upper VA region that it shares with the kernel, modules and
> vmalloc/vmap mappings once we enable LPA2 with 4k pages.
> 
> The next ~30 patches rework the early init code, reimplementing most of
> the page table and relocation handling in C code. There are several
> reasons why this is beneficial:
> - we generally prefer C code over asm for these things, and the macros
>   that currently exist in head.S for creating the kernel pages tables
>   are a good example why;
> - we no longer need to create the kernel mapping in two passes, which
>   means we can remove the logic that copies parts of the fixmap and the
>   KAsan shadow from one set of page tables to the other; this is
>   especially advantageous for KAsan with LPA2, which needs more
>   elaborate shadow handling across multiple levels, since the KAsan
>   region cannot be placed on exact pgd_t bouundaries in that case;
> - we can read the ID registers and parse command line overrides before
>   creating the page tables, which simplifies the LPA2 case, as flicking
>   the global TCR_EL1.DS bit at a later stage would require elaborate
>   repainting of all page table descriptors, some of which with the MMU
>   disabled;
> - we can use more elaborate logic to create the mappings, which means we
>   can use more precise mappings for code and data sections even when
>   using 2 MiB granularity, and this is a prerequisite for running with
>   WXN.
> 
> As part of the ID map changes, we decouple the ID map size from the
> kernel VA size, and switch to a 48-bit VA map for all configurations.
> 
> The next 18 patches rework the existing LVA support as a CPU feature,
> which simplifies some code and gets rid of the vabits_actual variable.
> Then, LPA2 support is implemented in the same vein. This requires adding
> support for 5 level paging as well, given that LPA2 introduces a new
> paging level '-1' when using 4k pages.
> 
> Combined with the vmemmap changes at the start of the series, the
> resulting LPA2/4k pages configuration will have the exact same VA space
> layout as the ordinary 4k/4 levels configuration, and so LPA2 support
> can reasonably be enabled by default, as the fallback is seamless on
> non-LPA2 hardware.
> 
> In the 16k/LPA2 case, the fallback also reduces the number of paging
> levels, resulting in a 47-bit VA space. This is based on the assumption
> that hybrid LPA2/non-LPA2 16k pages kernels in production use would
> prefer not to take the performance hit of 4 level paging to gain only a
> single additional bit of VA space. (Note that generic Android kernels
> use only 3 levels of paging today.) Bespoke 16k configurations can still
> configure 48-bit virtual addressing as before.
> 
> Finally, the last two patches enable support for running with the WXN
> control enabled. This was previously part of a separate series [1], but
> given that the delta is tiny, it is included here as well.
> 
> [0] https://lore.kernel.org/all/20221124123932.2648991-1-ardb@kernel.org/
> [1] https://lore.kernel.org/all/20221111171201.2088501-1-ardb@kernel.org/
> 
> Cc: Catalin Marinas <catalin.marinas@arm.com>
> Cc: Will Deacon <will@kernel.org>
> Cc: Marc Zyngier <maz@kernel.org>
> Cc: Mark Rutland <mark.rutland@arm.com>
> Cc: Ryan Roberts <ryan.roberts@arm.com>
> Cc: Anshuman Khandual <anshuman.khandual@arm.com>
> Cc: Kees Cook <keescook@chromium.org>
> 
> Anshuman Khandual (2):
>   arm64/mm: Add FEAT_LPA2 specific TCR_EL1.DS field
>   arm64/mm: Add FEAT_LPA2 specific ID_AA64MMFR0.TGRAN[2]
> 
> Ard Biesheuvel (57):
> 
>   // KASLR / vmemmap reorg
>   arm64: kernel: Disable latent_entropy GCC plugin in early C runtime
>   arm64: mm: Take potential load offset into account when KASLR is off
>   arm64: mm: get rid of kimage_vaddr global variable
>   arm64: mm: Move PCI I/O emulation region above the vmemmap region
>   arm64: mm: Move fixmap region above vmemmap region
>   arm64: ptdump: Allow VMALLOC_END to be defined at boot
>   arm64: ptdump: Discover start of vmemmap region at runtime
>   arm64: vmemmap: Avoid base2 order of struct page size to dimension
>     region
>   arm64: mm: Reclaim unused vmemmap region for vmalloc use
>   arm64: kaslr: Adjust randomization range dynamically
>   arm64: kaslr: drop special case for ThunderX in kaslr_requires_kpti()
>   arm64: kvm: honour 'nokaslr' command line option for the HYP VA space
> 
>   // Reimplement page table creation code in C
>   arm64: kernel: Manage absolute relocations in code built under pi/
>   arm64: kernel: Don't rely on objcopy to make code under pi/ __init
>   arm64: head: move relocation handling to C code
>   arm64: idreg-override: Omit non-NULL checks for override pointer
>   arm64: idreg-override: Prepare for place relative reloc patching
>   arm64: idreg-override: Avoid parameq() and parameqn()
>   arm64: idreg-override: avoid strlen() to check for empty strings
>   arm64: idreg-override: Avoid sprintf() for simple string concatenation
>   arm64: idreg-override: Avoid kstrtou64() to parse a single hex digit
>   arm64: idreg-override: Move to early mini C runtime
>   arm64: kernel: Remove early fdt remap code
>   arm64: head: Clear BSS and the kernel page tables in one go
>   arm64: Move feature overrides into the BSS section
>   arm64: head: Run feature override detection before mapping the kernel
>   arm64: head: move dynamic shadow call stack patching into early C
>     runtime
>   arm64: kaslr: Use feature override instead of parsing the cmdline
>     again
>   arm64: idreg-override: Create a pseudo feature for rodata=off
>   arm64: Add helpers to probe local CPU for PAC/BTI/E0PD support
>   arm64: head: allocate more pages for the kernel mapping
>   arm64: head: move memstart_offset_seed handling to C code
>   arm64: head: Move early kernel mapping routines into C code
>   arm64: mm: Use 48-bit virtual addressing for the permanent ID map
>   arm64: pgtable: Decouple PGDIR size macros from PGD/PUD/PMD levels
>   arm64: kernel: Create initial ID map from C code
>   arm64: mm: avoid fixmap for early swapper_pg_dir updates
>   arm64: mm: omit redundant remap of kernel image
>   arm64: Revert "mm: provide idmap pointer to cpu_replace_ttbr1()"
> 
>   // Implement LPA2 support
>   arm64: mm: Handle LVA support as a CPU feature
>   arm64: mm: Add feature override support for LVA
>   arm64: mm: Wire up TCR.DS bit to PTE shareability fields
>   arm64: mm: Add LPA2 support to phys<->pte conversion routines
>   arm64: mm: Add definitions to support 5 levels of paging
>   arm64: mm: add LPA2 and 5 level paging support to G-to-nG conversion
>   arm64: Enable LPA2 at boot if supported by the system
>   arm64: mm: Add 5 level paging support to fixmap and swapper handling
>   arm64: kasan: Reduce minimum shadow alignment and enable 5 level
>     paging
>   arm64: mm: Add support for folding PUDs at runtime
>   arm64: ptdump: Disregard unaddressable VA space
>   arm64: ptdump: Deal with translation levels folded at runtime
>   arm64: kvm: avoid CONFIG_PGTABLE_LEVELS for runtime levels
>   arm64: kvm: Limit HYP VA and host S2 range to 48 bits when LPA2 is in
>     effect
>   arm64: Enable 52-bit virtual addressing for 4k and 16k granule configs
>   arm64: defconfig: Enable LPA2 support
> 
>   // Allow WXN control to be enabled at boot
>   mm: add arch hook to validate mmap() prot flags
>   arm64: mm: add support for WXN memory translation attribute
> 
> Marc Zyngier (1):
>   arm64: Turn kaslr_feature_override into a generic SW feature override
> 
>  arch/arm64/Kconfig                      |  34 +-
>  arch/arm64/configs/defconfig            |   2 +-
>  arch/arm64/include/asm/assembler.h      |  55 +--
>  arch/arm64/include/asm/cpufeature.h     | 102 +++++
>  arch/arm64/include/asm/fixmap.h         |   1 +
>  arch/arm64/include/asm/kasan.h          |   2 -
>  arch/arm64/include/asm/kernel-pgtable.h | 104 ++---
>  arch/arm64/include/asm/memory.h         |  50 +--
>  arch/arm64/include/asm/mman.h           |  36 ++
>  arch/arm64/include/asm/mmu.h            |  26 +-
>  arch/arm64/include/asm/mmu_context.h    |  49 ++-
>  arch/arm64/include/asm/pgalloc.h        |  53 ++-
>  arch/arm64/include/asm/pgtable-hwdef.h  |  33 +-
>  arch/arm64/include/asm/pgtable-prot.h   |  18 +-
>  arch/arm64/include/asm/pgtable-types.h  |   6 +
>  arch/arm64/include/asm/pgtable.h        | 229 +++++++++-
>  arch/arm64/include/asm/scs.h            |  34 +-
>  arch/arm64/include/asm/setup.h          |   3 -
>  arch/arm64/include/asm/sysreg.h         |   2 +
>  arch/arm64/include/asm/tlb.h            |   3 +-
>  arch/arm64/kernel/Makefile              |   7 +-
>  arch/arm64/kernel/cpu_errata.c          |   2 +-
>  arch/arm64/kernel/cpufeature.c          |  90 ++--
>  arch/arm64/kernel/head.S                | 465 ++------------------
>  arch/arm64/kernel/idreg-override.c      | 322 --------------
>  arch/arm64/kernel/image-vars.h          |  32 ++
>  arch/arm64/kernel/kaslr.c               |   4 +-
>  arch/arm64/kernel/module.c              |   2 +-
>  arch/arm64/kernel/pi/Makefile           |  28 +-
>  arch/arm64/kernel/pi/idreg-override.c   | 396 +++++++++++++++++
>  arch/arm64/kernel/pi/kaslr_early.c      |  78 +---
>  arch/arm64/kernel/pi/map_kernel.c       | 284 ++++++++++++
>  arch/arm64/kernel/pi/map_range.c        | 104 +++++
>  arch/arm64/kernel/{ => pi}/patch-scs.c  |  36 +-
>  arch/arm64/kernel/pi/pi.h               |  30 ++
>  arch/arm64/kernel/pi/relacheck.c        | 130 ++++++
>  arch/arm64/kernel/pi/relocate.c         |  64 +++
>  arch/arm64/kernel/setup.c               |  22 -
>  arch/arm64/kernel/sleep.S               |   3 -
>  arch/arm64/kernel/suspend.c             |   2 +-
>  arch/arm64/kernel/vmlinux.lds.S         |  14 +-
>  arch/arm64/kvm/hyp/nvhe/mem_protect.c   |   2 +
>  arch/arm64/kvm/mmu.c                    |  22 +-
>  arch/arm64/kvm/va_layout.c              |  10 +-
>  arch/arm64/mm/init.c                    |   2 +-
>  arch/arm64/mm/kasan_init.c              | 154 +++++--
>  arch/arm64/mm/mmap.c                    |   4 +
>  arch/arm64/mm/mmu.c                     | 268 ++++++-----
>  arch/arm64/mm/pgd.c                     |  17 +-
>  arch/arm64/mm/proc.S                    | 106 ++++-
>  arch/arm64/mm/ptdump.c                  |  43 +-
>  arch/arm64/tools/cpucaps                |   1 +
>  include/linux/mman.h                    |  15 +
>  mm/mmap.c                               |   3 +
>  54 files changed, 2259 insertions(+), 1345 deletions(-)
>  delete mode 100644 arch/arm64/kernel/idreg-override.c
>  create mode 100644 arch/arm64/kernel/pi/idreg-override.c
>  create mode 100644 arch/arm64/kernel/pi/map_kernel.c
>  create mode 100644 arch/arm64/kernel/pi/map_range.c
>  rename arch/arm64/kernel/{ => pi}/patch-scs.c (89%)
>  create mode 100644 arch/arm64/kernel/pi/pi.h
>  create mode 100644 arch/arm64/kernel/pi/relacheck.c
>  create mode 100644 arch/arm64/kernel/pi/relocate.c
>
  

On Tue, 7 Mar 2023 at 17:28, Ryan Roberts <ryan.roberts@arm.com> wrote:
>
> Hi Ard,
>
> Just to say that I plan to work my way through this lot over the next couple of
> weeks. I hope you can tolerate comments dribbling in as I go?
>

Yes, please take the time you need. I am confident we will still be
able to comfortably beat actual LPA2 hardware coming to market.
  

On 07/03/2023 14:04, Ard Biesheuvel wrote:
> This is a followup to [0], which was a lot smaller. Thanks to Ryan for
> feedback and review. This series is independent from Ryan's work on
> adding support for LPA2 to KVM - the only potential source of conflict
> should be the patch "arm64: kvm: Limit HYP VA and host S2 range to 48
> bits when LPA2 is in effect", which could simply be dropped in favour of
> the KVM changes to make it support LPA2.
> 
> The first ~15 patches of this series rework how the kernel VA space is
> organized, so that the vmemmap region does not take up more space than
> necessary, and so that most of it can be reclaimed when running a build
> capable of 52-bit virtual addressing on hardware that is not. This is
> needed because the vmemmap region will take up a substantial part of the
> upper VA region that it shares with the kernel, modules and
> vmalloc/vmap mappings once we enable LPA2 with 4k pages.
> 
> The next ~30 patches rework the early init code, reimplementing most of
> the page table and relocation handling in C code. There are several
> reasons why this is beneficial:
> - we generally prefer C code over asm for these things, and the macros
>   that currently exist in head.S for creating the kernel pages tables
>   are a good example why;
> - we no longer need to create the kernel mapping in two passes, which
>   means we can remove the logic that copies parts of the fixmap and the
>   KAsan shadow from one set of page tables to the other; this is
>   especially advantageous for KAsan with LPA2, which needs more
>   elaborate shadow handling across multiple levels, since the KAsan
>   region cannot be placed on exact pgd_t bouundaries in that case;
> - we can read the ID registers and parse command line overrides before
>   creating the page tables, which simplifies the LPA2 case, as flicking
>   the global TCR_EL1.DS bit at a later stage would require elaborate
>   repainting of all page table descriptors, some of which with the MMU
>   disabled;
> - we can use more elaborate logic to create the mappings, which means we
>   can use more precise mappings for code and data sections even when
>   using 2 MiB granularity, and this is a prerequisite for running with
>   WXN.
> 
> As part of the ID map changes, we decouple the ID map size from the
> kernel VA size, and switch to a 48-bit VA map for all configurations.
> 
> The next 18 patches rework the existing LVA support as a CPU feature,
> which simplifies some code and gets rid of the vabits_actual variable.
> Then, LPA2 support is implemented in the same vein. This requires adding
> support for 5 level paging as well, given that LPA2 introduces a new
> paging level '-1' when using 4k pages.

I still don't see any changes for TLBI, which I raised in the first round, and
which I think you need when enabling LPA2. I have 2 patches, which I think are
appropriate; one covers the non-range tlbi routines (and is part of my KVM
series) and the other covers the rage-based routines (this would need a bit of
fix up to use your lpa2_is_enabled()). At [1] and [2] respectively.

[1] https://lore.kernel.org/kvmarm/20230306195438.1557851-2-ryan.roberts@arm.com/
[2]
https://gitlab.arm.com/linux-arm/linux-rr/-/commit/38628decb785aea42a349a857b9f8a65a19e9c2b

Thanks,
Ryan