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    Subject[PATCH 5.6 002/194] kvm: nVMX: reflect MTF VM-exits if injected by L1
    Date
    From: Oliver Upton <oupton@google.com>

    [ Upstream commit b045ae906b42afb361dc7ecf1a3cea110fb0a65f ]

    According to SDM 26.6.2, it is possible to inject an MTF VM-exit via the
    VM-entry interruption-information field regardless of the 'monitor trap
    flag' VM-execution control. KVM appropriately copies the VM-entry
    interruption-information field from vmcs12 to vmcs02. However, if L1
    has not set the 'monitor trap flag' VM-execution control, KVM fails to
    reflect the subsequent MTF VM-exit into L1.

    Fix this by consulting the VM-entry interruption-information field of
    vmcs12 to determine if L1 has injected the MTF VM-exit. If so, reflect
    the exit, regardless of the 'monitor trap flag' VM-execution control.

    Fixes: 5f3d45e7f282 ("kvm/x86: add support for MONITOR_TRAP_FLAG")
    Signed-off-by: Oliver Upton <oupton@google.com>
    Reviewed-by: Peter Shier <pshier@google.com>
    Reviewed-by: Jim Mattson <jmattson@google.com>
    Message-Id: <20200414224746.240324-1-oupton@google.com>
    Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
    Signed-off-by: Sasha Levin <sashal@kernel.org>
    ---
    arch/x86/kvm/vmx/nested.c | 19 ++++++++++++++++++-
    1 file changed, 18 insertions(+), 1 deletion(-)

    diff --git a/arch/x86/kvm/vmx/nested.c b/arch/x86/kvm/vmx/nested.c
    index b773989308015..3a2f05ef51fa4 100644
    --- a/arch/x86/kvm/vmx/nested.c
    +++ b/arch/x86/kvm/vmx/nested.c
    @@ -5504,6 +5504,23 @@ static bool nested_vmx_exit_handled_vmcs_access(struct kvm_vcpu *vcpu,
    return 1 & (b >> (field & 7));
    }

    +static bool nested_vmx_exit_handled_mtf(struct vmcs12 *vmcs12)
    +{
    + u32 entry_intr_info = vmcs12->vm_entry_intr_info_field;
    +
    + if (nested_cpu_has_mtf(vmcs12))
    + return true;
    +
    + /*
    + * An MTF VM-exit may be injected into the guest by setting the
    + * interruption-type to 7 (other event) and the vector field to 0. Such
    + * is the case regardless of the 'monitor trap flag' VM-execution
    + * control.
    + */
    + return entry_intr_info == (INTR_INFO_VALID_MASK
    + | INTR_TYPE_OTHER_EVENT);
    +}
    +
    /*
    * Return 1 if we should exit from L2 to L1 to handle an exit, or 0 if we
    * should handle it ourselves in L0 (and then continue L2). Only call this
    @@ -5618,7 +5635,7 @@ bool nested_vmx_exit_reflected(struct kvm_vcpu *vcpu, u32 exit_reason)
    case EXIT_REASON_MWAIT_INSTRUCTION:
    return nested_cpu_has(vmcs12, CPU_BASED_MWAIT_EXITING);
    case EXIT_REASON_MONITOR_TRAP_FLAG:
    - return nested_cpu_has_mtf(vmcs12);
    + return nested_vmx_exit_handled_mtf(vmcs12);
    case EXIT_REASON_MONITOR_INSTRUCTION:
    return nested_cpu_has(vmcs12, CPU_BASED_MONITOR_EXITING);
    case EXIT_REASON_PAUSE_INSTRUCTION:
    --
    2.20.1


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