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    Subject[PATCH 5.12 070/700] KVM: nVMX: Handle split-lock #AC exceptions that happen in L2
    Date
    From: Sean Christopherson <seanjc@google.com>

    commit b33bb78a1fada6445c265c585ee0dd0fc6279102 upstream.

    Mark #ACs that won't be reinjected to the guest as wanted by L0 so that
    KVM handles split-lock #AC from L2 instead of forwarding the exception to
    L1. Split-lock #AC isn't yet virtualized, i.e. L1 will treat it like a
    regular #AC and do the wrong thing, e.g. reinject it into L2.

    Fixes: e6f8b6c12f03 ("KVM: VMX: Extend VMXs #AC interceptor to handle split lock #AC in guest")
    Cc: Xiaoyao Li <xiaoyao.li@intel.com>
    Signed-off-by: Sean Christopherson <seanjc@google.com>
    Message-Id: <20210622172244.3561540-1-seanjc@google.com>
    Cc: stable@vger.kernel.org
    Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

    ---
    arch/x86/kvm/vmx/nested.c | 3 +++
    arch/x86/kvm/vmx/vmcs.h | 5 +++++
    arch/x86/kvm/vmx/vmx.c | 4 ++--
    arch/x86/kvm/vmx/vmx.h | 1 +
    4 files changed, 11 insertions(+), 2 deletions(-)

    --- a/arch/x86/kvm/vmx/nested.c
    +++ b/arch/x86/kvm/vmx/nested.c
    @@ -5775,6 +5775,9 @@ static bool nested_vmx_l0_wants_exit(str
    else if (is_breakpoint(intr_info) &&
    vcpu->guest_debug & KVM_GUESTDBG_USE_SW_BP)
    return true;
    + else if (is_alignment_check(intr_info) &&
    + !vmx_guest_inject_ac(vcpu))
    + return true;
    return false;
    case EXIT_REASON_EXTERNAL_INTERRUPT:
    return true;
    --- a/arch/x86/kvm/vmx/vmcs.h
    +++ b/arch/x86/kvm/vmx/vmcs.h
    @@ -117,6 +117,11 @@ static inline bool is_gp_fault(u32 intr_
    return is_exception_n(intr_info, GP_VECTOR);
    }

    +static inline bool is_alignment_check(u32 intr_info)
    +{
    + return is_exception_n(intr_info, AC_VECTOR);
    +}
    +
    static inline bool is_machine_check(u32 intr_info)
    {
    return is_exception_n(intr_info, MC_VECTOR);
    --- a/arch/x86/kvm/vmx/vmx.c
    +++ b/arch/x86/kvm/vmx/vmx.c
    @@ -4796,7 +4796,7 @@ static int handle_machine_check(struct k
    * - Guest has #AC detection enabled in CR0
    * - Guest EFLAGS has AC bit set
    */
    -static inline bool guest_inject_ac(struct kvm_vcpu *vcpu)
    +bool vmx_guest_inject_ac(struct kvm_vcpu *vcpu)
    {
    if (!boot_cpu_has(X86_FEATURE_SPLIT_LOCK_DETECT))
    return true;
    @@ -4905,7 +4905,7 @@ static int handle_exception_nmi(struct k
    kvm_run->debug.arch.exception = ex_no;
    break;
    case AC_VECTOR:
    - if (guest_inject_ac(vcpu)) {
    + if (vmx_guest_inject_ac(vcpu)) {
    kvm_queue_exception_e(vcpu, AC_VECTOR, error_code);
    return 1;
    }
    --- a/arch/x86/kvm/vmx/vmx.h
    +++ b/arch/x86/kvm/vmx/vmx.h
    @@ -379,6 +379,7 @@ void vmx_set_segment(struct kvm_vcpu *vc
    u64 construct_eptp(struct kvm_vcpu *vcpu, unsigned long root_hpa,
    int root_level);

    +bool vmx_guest_inject_ac(struct kvm_vcpu *vcpu);
    void vmx_update_exception_bitmap(struct kvm_vcpu *vcpu);
    void vmx_update_msr_bitmap(struct kvm_vcpu *vcpu);
    bool vmx_nmi_blocked(struct kvm_vcpu *vcpu);

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