[RFC PATCH v4 00/26] KVM: arm64: Make CPU ID registers writable by userspace

[Fuad Tabba]

Hi Reiji,

On Thu, Jan 6, 2022 at 4:27 AM Reiji Watanabe <reijiw at google.com> wrote:

> The patch series is for both VHE and non-VHE, except for protected VMs,
> which have a different way of configuring ID registers based on its
> different requirements [1].

I am reviewing this patch series and I really like your approach. I
think that once it's through we might be able to generalize it for
protected VMs as well (I did some of the work for the ID registers for
those).

> The series is based on v5.16-rc8 with the patch [3] applied.

I tried to apply this series on v5.16-rc8 after applying
20220104194918.373612-2-rananta at google.com, and it didn't apply
cleanly. If you could point me to a working branch that I could
checkout I would like to test it and experiment with it a bit more.

Thanks,
/fuad




> v4:
>   - Make ID registers storage per VM instead of per vCPU. [Marc]
>   - Implement arm64_check_features() in arch/arm64/kernel/cpufeature.c
>     by using existing codes in the file. [Marc]
>   - Use a configuration function to enable traps for disabled
>     features. [Marc]
>   - Document ID registers become immutable after the first KVM_RUN [Eric]
>   - Update ID_AA64PFR0.GIC at the point where a GICv3 is created. [Marc]
>   - Get TGranX's bit position by substracting 12 from TGranX_2's bit
>     position. [Eric]
>   - Don't validate AArch32 ID registers when the system doesn't support
>     32bit EL0. [Eric]
>   - Add/fixes comments for patches. [Eric]
>   - Made bug fixes/improvements of the selftest. [Eric]
>   - Added .kunitconfig for arm64 KUnit tests
>
> v3: https://lore.kernel.org/all/20211117064359.2362060-1-reijiw@google.com/
>   - Remove ID register consistency checking across vCPUs. [Oliver]
>   - Change KVM_CAP_ARM_ID_REG_WRITABLE to
>     KVM_CAP_ARM_ID_REG_CONFIGURABLE. [Oliver]
>   - Add KUnit testing for ID register validation and trap initialization.
>   - Change read_id_reg() to take care of ID_AA64PFR0_EL1.GIC.
>   - Add a helper of read_id_reg() (__read_id_reg()) and use the helper
>     instead of directly using __vcpu_sys_reg().
>   - Change not to run kvm_id_regs_consistency_check() and
>     kvm_vcpu_init_traps() for protected VMs.
>   - Update selftest to remove test cases for ID register consistency.
>     checking across vCPUs and to add test cases for ID_AA64PFR0_EL1.GIC.
>
> v2: https://lore.kernel.org/all/20211103062520.1445832-1-reijiw@google.com/
>   - Remove unnecessary line breaks. [Andrew]
>   - Use @params for comments. [Andrew]
>   - Move arm64_check_features to arch/arm64/kvm/sys_regs.c and
>     change that KVM specific feature check function.  [Andrew]
>   - Remove unnecessary raz handling from __set_id_reg. [Andrew]
>   - Remove sys_val field from the initial id_reg_info and add it
>     in the later patch. [Andrew]
>   - Call id_reg->init() from id_reg_info_init(). [Andrew]
>   - Fix cpuid_feature_cap_perfmon_field() to convert 0xf to 0x0
>     (and use it in the following patches).
>   - Change kvm_vcpu_first_run_init to set has_run_once to false
>     when kvm_id_regs_consistency_check() fails.
>   - Add a patch to introduce id_reg_info for ID_AA64MMFR0_EL1,
>     which requires special validity checking for TGran*_2 fields.
>   - Add patches to introduce id_reg_info for ID_DFR1_EL1 and
>     ID_MMFR0_EL1, which are required due to arm64_check_features
>     implementation change.
>   - Add a new argument, which is a pointer to id_reg_info, for
>     id_reg_info's validate().
>
> v1: https://lore.kernel.org/all/20211012043535.500493-1-reijiw@google.com/
>
> [1] https://lore.kernel.org/kvmarm/20211010145636.1950948-1-tabba@google.com/
> [2] https://lore.kernel.org/kvm/20201102033422.657391-1-liangpeng10@huawei.com/
> [3] https://lore.kernel.org/all/20220104194918.373612-2-rananta@google.com/
>
> Reiji Watanabe (26):
>   KVM: arm64: Introduce a validation function for an ID register
>   KVM: arm64: Save ID registers' sanitized value per guest
>   KVM: arm64: Introduce struct id_reg_info
>   KVM: arm64: Make ID_AA64PFR0_EL1 writable
>   KVM: arm64: Make ID_AA64PFR1_EL1 writable
>   KVM: arm64: Make ID_AA64ISAR0_EL1 writable
>   KVM: arm64: Make ID_AA64ISAR1_EL1 writable
>   KVM: arm64: Make ID_AA64MMFR0_EL1 writable
>   KVM: arm64: Hide IMPLEMENTATION DEFINED PMU support for the guest
>   KVM: arm64: Make ID_AA64DFR0_EL1 writable
>   KVM: arm64: Make ID_DFR0_EL1 writable
>   KVM: arm64: Make MVFR1_EL1 writable
>   KVM: arm64: Make ID registers without id_reg_info writable
>   KVM: arm64: Add consistency checking for frac fields of ID registers
>   KVM: arm64: Introduce KVM_CAP_ARM_ID_REG_CONFIGURABLE capability
>   KVM: arm64: Add kunit test for ID register validation
>   KVM: arm64: Use vcpu->arch cptr_el2 to track value of cptr_el2 for VHE
>   KVM: arm64: Use vcpu->arch.mdcr_el2 to track value of mdcr_el2
>   KVM: arm64: Introduce framework to trap disabled features
>   KVM: arm64: Trap disabled features of ID_AA64PFR0_EL1
>   KVM: arm64: Trap disabled features of ID_AA64PFR1_EL1
>   KVM: arm64: Trap disabled features of ID_AA64DFR0_EL1
>   KVM: arm64: Trap disabled features of ID_AA64MMFR1_EL1
>   KVM: arm64: Trap disabled features of ID_AA64ISAR1_EL1
>   KVM: arm64: Add kunit test for trap initialization
>   KVM: arm64: selftests: Introduce id_reg_test
>
>  Documentation/virt/kvm/api.rst                |   12 +
>  arch/arm64/include/asm/cpufeature.h           |    3 +-
>  arch/arm64/include/asm/kvm_arm.h              |   32 +
>  arch/arm64/include/asm/kvm_host.h             |   19 +
>  arch/arm64/include/asm/sysreg.h               |    3 +
>  arch/arm64/kernel/cpufeature.c                |  228 +++
>  arch/arm64/kvm/.kunitconfig                   |    4 +
>  arch/arm64/kvm/Kconfig                        |   11 +
>  arch/arm64/kvm/arm.c                          |   24 +-
>  arch/arm64/kvm/debug.c                        |   13 +-
>  arch/arm64/kvm/hyp/vhe/switch.c               |   14 +-
>  arch/arm64/kvm/sys_regs.c                     | 1329 +++++++++++++++--
>  arch/arm64/kvm/sys_regs_test.c                | 1247 ++++++++++++++++
>  arch/arm64/kvm/vgic/vgic-init.c               |    5 +
>  include/uapi/linux/kvm.h                      |    1 +
>  tools/arch/arm64/include/asm/sysreg.h         |    1 +
>  tools/testing/selftests/kvm/.gitignore        |    1 +
>  tools/testing/selftests/kvm/Makefile          |    1 +
>  .../selftests/kvm/aarch64/id_reg_test.c       | 1239 +++++++++++++++
>  19 files changed, 4041 insertions(+), 146 deletions(-)
>  create mode 100644 arch/arm64/kvm/.kunitconfig
>  create mode 100644 arch/arm64/kvm/sys_regs_test.c
>  create mode 100644 tools/testing/selftests/kvm/aarch64/id_reg_test.c
>
>
> base-commit: d399b107ee49bf5ea0391bd7614d512809e927b0
> --
> 2.34.1.448.ga2b2bfdf31-goog
>
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