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    Subject[PATCH v5 15/17] KVM: arm64: Implement non-protected nVHE hyp stack unwinder
    From
    Implements the common framework necessary for unwind() to work
    for non-protected nVHE mode:
    - on_accessible_stack()
    - on_overflow_stack()
    - unwind_next()

    Non-protected nVHE unwind() is used to unwind and dump the hypervisor
    stacktrace by the host in EL1

    Signed-off-by: Kalesh Singh <kaleshsingh@google.com>
    ---

    Changes in v5:
    - Use regular comments instead of doc comments, per Fuad

    arch/arm64/include/asm/stacktrace/nvhe.h | 67 +++++++++++++++++++++++-
    arch/arm64/kvm/arm.c | 2 +-
    2 files changed, 66 insertions(+), 3 deletions(-)

    diff --git a/arch/arm64/include/asm/stacktrace/nvhe.h b/arch/arm64/include/asm/stacktrace/nvhe.h
    index c3688e717136..7a6e761aa443 100644
    --- a/arch/arm64/include/asm/stacktrace/nvhe.h
    +++ b/arch/arm64/include/asm/stacktrace/nvhe.h
    @@ -120,15 +120,78 @@ NOKPROBE_SYMBOL(unwind_next);
    * (by the host in EL1).
    */

    +DECLARE_KVM_NVHE_PER_CPU(unsigned long [PAGE_SIZE/sizeof(long)], overflow_stack);
    +DECLARE_KVM_NVHE_PER_CPU(struct kvm_nvhe_stacktrace_info, kvm_stacktrace_info);
    +DECLARE_PER_CPU(unsigned long, kvm_arm_hyp_stack_page);
    +
    +/*
    + * kvm_nvhe_stack_kern_va - Convert KVM nVHE HYP stack addresses to a kernel VAs
    + *
    + * The nVHE hypervisor stack is mapped in the flexible 'private' VA range, to
    + * allow for guard pages below the stack. Consequently, the fixed offset address
    + * translation macros won't work here.
    + *
    + * The kernel VA is calculated as an offset from the kernel VA of the hypervisor
    + * stack base.
    + *
    + * Returns true on success and updates @addr to its corresponding kernel VA;
    + * otherwise returns false.
    + */
    +static inline bool kvm_nvhe_stack_kern_va(unsigned long *addr,
    + enum stack_type type)
    +{
    + struct kvm_nvhe_stacktrace_info *stacktrace_info;
    + unsigned long hyp_base, kern_base, hyp_offset;
    +
    + stacktrace_info = this_cpu_ptr_nvhe_sym(kvm_stacktrace_info);
    +
    + switch (type) {
    + case STACK_TYPE_HYP:
    + kern_base = (unsigned long)*this_cpu_ptr(&kvm_arm_hyp_stack_page);
    + hyp_base = (unsigned long)stacktrace_info->stack_base;
    + break;
    + case STACK_TYPE_OVERFLOW:
    + kern_base = (unsigned long)this_cpu_ptr_nvhe_sym(overflow_stack);
    + hyp_base = (unsigned long)stacktrace_info->overflow_stack_base;
    + break;
    + default:
    + return false;
    + }
    +
    + hyp_offset = *addr - hyp_base;
    +
    + *addr = kern_base + hyp_offset;
    +
    + return true;
    +}
    +
    static inline bool on_overflow_stack(unsigned long sp, unsigned long size,
    struct stack_info *info)
    {
    - return false;
    + struct kvm_nvhe_stacktrace_info *stacktrace_info
    + = this_cpu_ptr_nvhe_sym(kvm_stacktrace_info);
    + unsigned long low = (unsigned long)stacktrace_info->overflow_stack_base;
    + unsigned long high = low + OVERFLOW_STACK_SIZE;
    +
    + return on_stack(sp, size, low, high, STACK_TYPE_OVERFLOW, info);
    +}
    +
    +static inline bool on_hyp_stack(unsigned long sp, unsigned long size,
    + struct stack_info *info)
    +{
    + struct kvm_nvhe_stacktrace_info *stacktrace_info
    + = this_cpu_ptr_nvhe_sym(kvm_stacktrace_info);
    + unsigned long low = (unsigned long)stacktrace_info->stack_base;
    + unsigned long high = low + PAGE_SIZE;
    +
    + return on_stack(sp, size, low, high, STACK_TYPE_HYP, info);
    }

    static inline int notrace unwind_next(struct unwind_state *state)
    {
    - return 0;
    + struct stack_info info;
    +
    + return unwind_next_common(state, &info, kvm_nvhe_stack_kern_va);
    }
    NOKPROBE_SYMBOL(unwind_next);

    diff --git a/arch/arm64/kvm/arm.c b/arch/arm64/kvm/arm.c
    index a0188144a122..6a64293108c5 100644
    --- a/arch/arm64/kvm/arm.c
    +++ b/arch/arm64/kvm/arm.c
    @@ -49,7 +49,7 @@ DEFINE_STATIC_KEY_FALSE(kvm_protected_mode_initialized);

    DECLARE_KVM_HYP_PER_CPU(unsigned long, kvm_hyp_vector);

    -static DEFINE_PER_CPU(unsigned long, kvm_arm_hyp_stack_page);
    +DEFINE_PER_CPU(unsigned long, kvm_arm_hyp_stack_page);
    unsigned long kvm_arm_hyp_percpu_base[NR_CPUS];
    DECLARE_KVM_NVHE_PER_CPU(struct kvm_nvhe_init_params, kvm_init_params);

    --
    2.37.0.170.g444d1eabd0-goog
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