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

Marc Zyngier
2023-06-09T16:22:21Z

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(-)

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2.34.1