Re: [PATCH v3 00/17] KVM: arm64: Allow using VHE in the nVHE hypervisor

Marc Zyngier
2023-06-09T16:54:32Z

+ Catalin, as this changes a bunch of arch stuff (nothing major, but
still...)

On Fri, 09 Jun 2023 17:21:43 +0100,
Marc Zyngier <maz@kernel.org> wrote:
>
> KVM (on ARMv8.0) and pKVM (on all revisions of the architecture) use
> the split hypervisor model that makes the EL2 code more or less
> standalone. In the later case, we totally ignore the VHE mode and
> stick with the good old v8.0 EL2 setup.
>
> This is all good, but means that the EL2 code is limited in what it
> can do with its own address space. This series proposes to remove this
> limitation and to allow VHE to be used even with the split hypervisor
> model. This has some potential isolation benefits[1], and eventually
> allow systems that do not support HCR_EL2.E2H==0 to run pKVM.
>
> We introduce a new "mode" for KVM called hVHE, in reference to the
> nVHE mode, and indicating that only the hypervisor is using VHE. Note
> that this is all this series does. No effort is made to improve the VA
> space management, which will be the subject of another series if this
> one ever makes it.
>
> This has been tested on a M1 box (bare metal) as well as as a nested
> guest on M2, both with the standard nVHE and protected modes, with no
> measurable change in performance.
>
> Note: the last patch of this series is not a merge candidate.
>
> Thanks,
>
> M.
>
> [1] https://www.youtube.com/watch?v=1F_Mf2j9eIo&list=PLbzoR-pLrL6qWL3v2KOcvwZ54-w0z5uXV&index=11
>
> * From v2:
> - Use BUILD_BUG_ON() to prevent the use of is_kernel_in_hyp_mode()
> form hypervisor context
> - Validate that all CPUs are VHE-capable before flipping the
> capability
>
> * From v1:
> - Fixed CNTHCTL_EL2 setup when switching from E2H=0 to E2H=1
> Amusingly, this was found on NV...
> - Rebased on 6.4-rc2
>
> Marc Zyngier (17):
> KVM: arm64: Drop is_kernel_in_hyp_mode() from
> __invalidate_icache_guest_page()
> arm64: Prevent the use of is_kernel_in_hyp_mode() in hypervisor code
> arm64: Turn kaslr_feature_override into a generic SW feature override
> arm64: Add KVM_HVHE capability and has_hvhe() predicate
> arm64: Don't enable VHE for the kernel if OVERRIDE_HVHE is set
> arm64: Allow EL1 physical timer access when running VHE
> arm64: Use CPACR_EL1 format to set CPTR_EL2 when E2H is set
> KVM: arm64: Remove alternatives from sysreg accessors in VHE
> hypervisor context
> KVM: arm64: Key use of VHE instructions in nVHE code off
> ARM64_KVM_HVHE
> KVM: arm64: Force HCR_EL2.E2H when ARM64_KVM_HVHE is set
> KVM: arm64: Disable TTBR1_EL2 when using ARM64_KVM_HVHE
> KVM: arm64: Adjust EL2 stage-1 leaf AP bits when ARM64_KVM_HVHE is set
> KVM: arm64: Rework CPTR_EL2 programming for HVHE configuration
> KVM: arm64: Program the timer traps with VHE layout in hVHE mode
> KVM: arm64: Force HCR_E2H in guest context when ARM64_KVM_HVHE is set
> arm64: Allow arm64_sw.hvhe on command line
> KVM: arm64: Terrible timer hack for M1 with hVHE
>
> arch/arm64/include/asm/arch_timer.h | 8 ++++
> arch/arm64/include/asm/cpufeature.h | 5 +++
> arch/arm64/include/asm/el2_setup.h | 26 ++++++++++++-
> arch/arm64/include/asm/kvm_arm.h | 4 +-
> arch/arm64/include/asm/kvm_asm.h | 1 +
> arch/arm64/include/asm/kvm_emulate.h | 33 +++++++++++++++-
> arch/arm64/include/asm/kvm_hyp.h | 37 +++++++++++++-----
> arch/arm64/include/asm/kvm_mmu.h | 3 +-
> arch/arm64/include/asm/virt.h | 12 +++++-
> arch/arm64/kernel/cpufeature.c | 21 +++++++++++
> arch/arm64/kernel/hyp-stub.S | 10 ++++-
> arch/arm64/kernel/idreg-override.c | 25 ++++++++-----
> arch/arm64/kernel/image-vars.h | 3 ++
> arch/arm64/kernel/kaslr.c | 6 +--
> arch/arm64/kvm/arch_timer.c | 5 +++
> arch/arm64/kvm/arm.c | 12 +++++-
> arch/arm64/kvm/fpsimd.c | 4 +-
> arch/arm64/kvm/hyp/include/hyp/switch.h | 2 +-
> arch/arm64/kvm/hyp/nvhe/hyp-init.S | 9 +++++
> arch/arm64/kvm/hyp/nvhe/hyp-main.c | 17 ++++++++-
> arch/arm64/kvm/hyp/nvhe/pkvm.c | 27 ++++++++++---
> arch/arm64/kvm/hyp/nvhe/switch.c | 28 ++++++++------
> arch/arm64/kvm/hyp/nvhe/timer-sr.c | 25 +++++++++++--
> arch/arm64/kvm/hyp/pgtable.c | 6 ++-
> arch/arm64/kvm/hyp/vhe/switch.c | 2 +-
> arch/arm64/kvm/sys_regs.c | 2 +-
> arch/arm64/tools/cpucaps | 1 +
> drivers/irqchip/irq-apple-aic.c | 50 ++++++++++++++++++++++++-
> 28 files changed, 320 insertions(+), 64 deletions(-)
>
> --
> 2.34.1
>
>
>

--
Without deviation from the norm, progress is not possible.