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    SubjectRe: [PATCH v4 00/23] arm64: Virtualization Host Extension support
    Date

    Marc Zyngier <marc.zyngier@arm.com> writes:

    > ARMv8.1 comes with the "Virtualization Host Extension" (VHE for
    > short), which enables simpler support of Type-2 hypervisors.
    >
    > This extension allows the kernel to directly run at EL2, and
    > significantly reduces the number of system registers shared between
    > host and guest, reducing the overhead of virtualization.
    >
    > In order to have the same kernel binary running on all versions of the
    > architecture, this series makes heavy use of runtime code patching.
    >
    > The first 22 patches massage the KVM code to deal with VHE and enable
    > Linux to run at EL2. The last patch catches an ugly case when VHE
    > capable CPUs are paired with some of their less capable siblings. This
    > should never happen, but hey...
    >
    > I have deliberately left out some of the more "advanced"
    > optimizations, as they are likely to distract the reviewer from the
    > core infrastructure, which is what I care about at the moment.
    >
    > Note: GDB is currently busted on VHE systems, as it checks for version
    > 6 on the debug architecture, while VHE is version 7. The
    > binutils people are on the case.

    I assume you are talking about ptrace debug here rather than guest
    debug?

    Anyway from a cursory inspection I didn't see anything to worry about
    from the guest debug side which is unchanged.

    Acked-by: Alex Bennée <alex.bennee@linaro.org>

    >
    > This has been tested on the FVP_Base_SLV-V8-A model, and based on
    > v4.5-rc3 + kvmarm/master. I've put a branch out on:
    >
    > git://git.kernel.org/pub/scm/linux/kernel/git/maz/arm-platforms.git kvm-arm64/vhe
    >
    > * From v3:
    > - Cleaned debug handling after comments from Catalin
    > - Added missing barriers in the panic patch
    > - Collected Rb and Acks from Christoffer and Catalin
    >
    > * From v2:
    > - Added support for perf to count kernel events in EL2
    > - Added support for EL2 breakpoints
    > - Moved the VTCR_EL2 setup from assembly to C
    > - Made the fault handling easier to understand (hopefuly)
    > - Plenty of smaller fixups
    >
    > * From v1:
    > - Full rewrite now that the World Switch is written in C code.
    > - Dropped the "early IRQ handling" for the moment.
    >
    > Marc Zyngier (23):
    > arm/arm64: KVM: Add hook for C-based stage2 init
    > arm64: KVM: Switch to C-based stage2 init
    > arm/arm64: Add new is_kernel_in_hyp_mode predicate
    > arm64: Allow the arch timer to use the HYP timer
    > arm64: Add ARM64_HAS_VIRT_HOST_EXTN feature
    > arm64: KVM: Skip HYP setup when already running in HYP
    > arm64: KVM: VHE: Patch out use of HVC
    > arm64: KVM: VHE: Patch out kern_hyp_va
    > arm64: KVM: VHE: Introduce unified system register accessors
    > arm64: KVM: VHE: Differenciate host/guest sysreg save/restore
    > arm64: KVM: VHE: Split save/restore of registers shared between guest
    > and host
    > arm64: KVM: VHE: Use unified system register accessors
    > arm64: KVM: VHE: Enable minimal sysreg save/restore
    > arm64: KVM: VHE: Make __fpsimd_enabled VHE aware
    > arm64: KVM: VHE: Implement VHE activate/deactivate_traps
    > arm64: KVM: VHE: Use unified sysreg accessors for timer
    > arm64: KVM: VHE: Add fpsimd enabling on guest access
    > arm64: KVM: VHE: Add alternative panic handling
    > arm64: KVM: Move most of the fault decoding to C
    > arm64: perf: Count EL2 events if the kernel is running in HYP
    > arm64: hw_breakpoint: Allow EL2 breakpoints if running in HYP
    > arm64: VHE: Add support for running Linux in EL2 mode
    > arm64: Panic when VHE and non VHE CPUs coexist
    >
    > arch/arm/include/asm/kvm_host.h | 4 +
    > arch/arm/include/asm/virt.h | 5 +
    > arch/arm/kvm/arm.c | 174 ++++++++++++++++++----------
    > arch/arm/kvm/mmu.c | 7 ++
    > arch/arm64/Kconfig | 13 +++
    > arch/arm64/include/asm/cpufeature.h | 3 +-
    > arch/arm64/include/asm/hw_breakpoint.h | 49 +++++---
    > arch/arm64/include/asm/kvm_arm.h | 6 +-
    > arch/arm64/include/asm/kvm_asm.h | 2 +
    > arch/arm64/include/asm/kvm_emulate.h | 3 +
    > arch/arm64/include/asm/kvm_host.h | 6 +
    > arch/arm64/include/asm/kvm_mmu.h | 12 +-
    > arch/arm64/include/asm/virt.h | 27 +++++
    > arch/arm64/kernel/asm-offsets.c | 3 -
    > arch/arm64/kernel/cpufeature.c | 11 ++
    > arch/arm64/kernel/head.S | 50 +++++++-
    > arch/arm64/kernel/perf_event.c | 14 ++-
    > arch/arm64/kernel/smp.c | 3 +
    > arch/arm64/kvm/hyp-init.S | 18 ---
    > arch/arm64/kvm/hyp.S | 7 ++
    > arch/arm64/kvm/hyp/Makefile | 1 +
    > arch/arm64/kvm/hyp/entry.S | 6 +
    > arch/arm64/kvm/hyp/hyp-entry.S | 109 ++++++------------
    > arch/arm64/kvm/hyp/hyp.h | 108 ++++++++++++++++--
    > arch/arm64/kvm/hyp/s2-setup.c | 44 +++++++
    > arch/arm64/kvm/hyp/switch.c | 202 +++++++++++++++++++++++++++++----
    > arch/arm64/kvm/hyp/sysreg-sr.c | 147 ++++++++++++++++--------
    > arch/arm64/kvm/hyp/timer-sr.c | 10 +-
    > drivers/clocksource/arm_arch_timer.c | 96 ++++++++++------
    > 29 files changed, 842 insertions(+), 298 deletions(-)
    > create mode 100644 arch/arm64/kvm/hyp/s2-setup.c


    --
    Alex Bennée

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