linux-kernel - [PATCH v4 00/10] Independent per-CPU data section for nVHE

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Message-Id: <20200922204910.7265-1-dbrazdil@google.com>
Date:   Tue, 22 Sep 2020 21:49:00 +0100
From:   David Brazdil <dbrazdil@...gle.com>
To:     kvmarm@...ts.cs.columbia.edu
Cc:     Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will@...nel.org>, Marc Zyngier <maz@...nel.org>,
        James Morse <james.morse@....com>,
        Julien Thierry <julien.thierry.kdev@...il.com>,
        Suzuki K Poulose <suzuki.poulose@....com>,
        Dennis Zhou <dennis@...nel.org>, Tejun Heo <tj@...nel.org>,
        Christoph Lameter <cl@...ux.com>,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        kernel-team@...roid.com, David Brazdil <dbrazdil@...gle.com>
Subject: [PATCH v4 00/10] Independent per-CPU data section for nVHE

Introduce '.hyp.data..percpu' as part of ongoing effort to make nVHE
hyp code self-contained and independent of the rest of the kernel.

Main benefits:
 * independent nVHE per-CPU data section that can be unmapped from host,
 * more robust linking of nVHE hyp code,
 * no need for hyp-specific macros to access per-CPU variables.

The series is structured as follows:

 - patch 1: Improve existing hyp build rules. This could be sent and merged
    independently of per-CPU but this series builds on it.

 - patches 2-3: Minor cleanups.

 - patches 4-5: Replace hyp helpers for accessing per-CPU variables
     with common helpers modified to work correctly in hyp. Per-CPU
     variables can now be accessed with one API anywhere.

 - patches 6-8: Where VHE and nVHE use per-CPU variables defined in
     kernel proper, move their definitions to hyp/ where they are
     duplicated and owned by VHE/nVHE, respectively. Non-VHE hyp code
     now refers only to per-CPU variables defined in its source files.
     Helpers are added so that kernel proper can continue to access
     nVHE hyp variables, same way as it does with other nVHE symbols.

 - patches 9-10: Introduce '.hyp.data..percpu' ELF section and allocate
     memory for every CPU core during KVM init. All nVHE per-CPU state
     is now grouped together in ELF and in memory. Introducing a new
     per-CPU variable does not require adding new memory mappings any
     more. nVHE hyp code cannot accidentally refer to kernel-proper
     per-CPU data as it only has the pointer to its own per-CPU memory.

Patches are rebased on v5.9-rc6 and available in branch 'topic/percpu-v4' at:
    https://android-kvm.googlesource.com/linux

For maintainers: In case of interest, there are patches that remove the need
for redefining macros under DEBUG_PREEMPT available at the same repo, branch
'topic/percpu-v3-debug-preempt'. Since they are non-trivial, I am not going
to post them here so late in the 5.10 window. I plan to post them for 5.11
when they will also be useful for other patches.

Changes v3 -> v4:
 * Drop patch that marked pages allocated for hyp reserved
 * Copy arm64_ssbd_callback_required at cpu_init_hyp_mode
 * Use read_sysreg in __hyp_my_cpu_offset
 * Simplify per-CPU region allocation code
 * Use same subsection name regex as other kernel linker scripts
 * Rename helper per-CPU macros
 * Add .gitignore for hyp linker script

Changes v2 -> v3:
 * Use PERCPU_INPUT in hyp.ld instead of modifying PERCPU_SECTION
 * Only pass linker script once to LD (fix error message)
 * Renamed '.hyp.o' to '.nvhe.o'
 * Use __KVM_VHE_HYPERVISOR__ to select TPIDR_EL2 instead of alternatives
 * Move all prefixing-related macros to hyp_image.h

Changes v1 -> v2:
 * partially link hyp code, add linker script

David Brazdil (10):
  kvm: arm64: Partially link nVHE hyp code, simplify HYPCOPY
  kvm: arm64: Move nVHE hyp namespace macros to hyp_image.h
  kvm: arm64: Only define __kvm_ex_table for CONFIG_KVM
  kvm: arm64: Remove __hyp_this_cpu_read
  kvm: arm64: Remove hyp_adr/ldr_this_cpu
  kvm: arm64: Add helpers for accessing nVHE hyp per-cpu vars
  kvm: arm64: Duplicate arm64_ssbd_callback_required for nVHE hyp
  kvm: arm64: Create separate instances of kvm_host_data for VHE/nVHE
  kvm: arm64: Set up hyp percpu data for nVHE
  kvm: arm64: Remove unnecessary hyp mappings

 arch/arm64/include/asm/assembler.h        | 29 +++++---
 arch/arm64/include/asm/hyp_image.h        | 36 ++++++++++
 arch/arm64/include/asm/kvm_asm.h          | 82 +++++++++++------------
 arch/arm64/include/asm/kvm_host.h         |  2 +-
 arch/arm64/include/asm/kvm_mmu.h          | 22 ++----
 arch/arm64/include/asm/percpu.h           | 28 +++++++-
 arch/arm64/kernel/image-vars.h            |  4 --
 arch/arm64/kernel/vmlinux.lds.S           | 13 ++++
 arch/arm64/kvm/arm.c                      | 61 +++++++++++++----
 arch/arm64/kvm/hyp/hyp-entry.S            |  2 +-
 arch/arm64/kvm/hyp/include/hyp/debug-sr.h |  4 +-
 arch/arm64/kvm/hyp/include/hyp/switch.h   |  8 +--
 arch/arm64/kvm/hyp/nvhe/.gitignore        |  2 +
 arch/arm64/kvm/hyp/nvhe/Makefile          | 60 +++++++++--------
 arch/arm64/kvm/hyp/nvhe/hyp.lds.S         | 19 ++++++
 arch/arm64/kvm/hyp/nvhe/switch.c          |  8 ++-
 arch/arm64/kvm/hyp/vhe/switch.c           |  5 +-
 arch/arm64/kvm/hyp/vhe/sysreg-sr.c        |  4 +-
 arch/arm64/kvm/pmu.c                      | 13 ++--
 19 files changed, 272 insertions(+), 130 deletions(-)
 create mode 100644 arch/arm64/include/asm/hyp_image.h
 create mode 100644 arch/arm64/kvm/hyp/nvhe/.gitignore
 create mode 100644 arch/arm64/kvm/hyp/nvhe/hyp.lds.S

--
2.28.0.681.g6f77f65b4e-goog