[PATCH v1 00/18] Permission Indirection Extension

[Joey Gouly]

Hi all,

This series implements the Permission Indirection Extension introduced in 2022
VMSA enhancements [1].

The Permission Indirection Extension is a new way to set memory permissions.
Instead of directly encoding the permission in the Page Table Entry (PTE),
fields in the PTEs are used to index into an array of permissions specified in
a register. This indirection provides greater flexibility, greater encoding
density and enables the representation of new permissions.

The PTEs bit that are repurposed for use with permission indirection are:
	54 PTE_UXN
	53 PTE_PXN
	51 PTE_DBM
	6 PTE_USER

The way that PIE is implemented in this patchset is that the encodings are
picked such that they match how Linux currently sets the bits in the PTEs, so
none of the page table handling has changed. This means this patchset keeps the
same functionality as currently implemented, but allows for future expansion.

Enabling PIE is also a prerequisite for implementing the Guarded Control Stack
Extension (GCS).

Another related extension is the Permission Overlay Extension, which is not
covered by this patch set, but is mentioned in patch 5 as half of PIE encoding
values apply an overlay. However, since overlays are not currently enabled, they
act as all the other permissions do.

This first few patches are adding the new system registers, and cpufeature
capabilities. Then KVM support for save/restore of the new registers is added.
Finally the new Permission Indirection registers are set and the new feature is
enabled.

There's two series on the ML that conflict-ish, but I don't think either will
tough to rework against:
  Kristina's series which changes how HCRX_EL2 works [2]
  Mark's commit to switch HFGxTR to automatic generation [3]

Thanks,
Joey

[1] https://community.arm.com/arm-community-blogs/b/architectures-and-processors-blog/posts/arm-a-profile-architecture-2022
[2] https://lore.kernel.org/linux-arm-kernel/20230216160012.272345-1-kristina.martsenko@arm.com/
[3] https://lore.kernel.org/linux-arm-kernel/20230306-arm64-fgt-reg-gen-v1-1-95bc0c97cfed@kernel.org/

Joey Gouly (18):
  arm64/sysreg: Add ID register ID_AA64MMFR3
  arm64/sysreg: add system registers TCR2_ELx
  arm64/sysreg: add TCR2En to HCRX_EL2
  arm64/sysreg: add HFGxTR_EL2 bits for Permission Indirection Extension
  arm64/sysreg: add PIR*_ELx registers
  arm64: cpufeature: add system register ID_AA64MMFR3
  arm64: cpufeature: add TCR2 cpucap
  arm64: cpufeature: add Permission Indirection Extension cpucap
  KVM: arm64: Save/restore TCR2_EL1
  KVM: arm64: Save/restore PIE registers
  KVM: arm64: expose ID_AA64MMFR3_EL1 to guests
  arm64: add PTE_UXN/PTE_WRITE to SWAPPER_*_FLAGS
  arm64: add PTE_WRITE to PROT_SECT_NORMAL
  arm64: reorganise PAGE_/PROT_ macros
  arm64: disable EL2 traps for PIE
  arm64: add encodings of PIRx_ELx registers
  arm64: enable Permission Indirection Extension (PIE)
  arm64: transfer permission indirection settings to EL2

 arch/arm64/include/asm/cpu.h               |   1 +
 arch/arm64/include/asm/el2_setup.h         |  27 ++++-
 arch/arm64/include/asm/kernel-pgtable.h    |   4 +-
 arch/arm64/include/asm/kvm_host.h          |   5 +
 arch/arm64/include/asm/pgtable-hwdef.h     |   8 ++
 arch/arm64/include/asm/pgtable-prot.h      |  90 ++++++++++-----
 arch/arm64/include/asm/pgtable.h           |   6 +
 arch/arm64/include/asm/sysreg.h            |  23 ++++
 arch/arm64/kernel/cpufeature.c             |  32 ++++++
 arch/arm64/kernel/cpuinfo.c                |   1 +
 arch/arm64/kernel/head.S                   |   8 +-
 arch/arm64/kernel/hyp-stub.S               |  18 +++
 arch/arm64/kvm/hyp/include/hyp/sysreg-sr.h |  12 ++
 arch/arm64/kvm/sys_regs.c                  |   2 +-
 arch/arm64/mm/proc.S                       |  17 ++-
 arch/arm64/tools/cpucaps                   |   2 +
 arch/arm64/tools/sysreg                    | 127 ++++++++++++++++++++-
 17 files changed, 345 insertions(+), 38 deletions(-)

-- 
2.17.1