1 files changed, 22 insertions, 4 deletions

diff --git a/arch/arm64/kvm/debug.c b/arch/arm64/kvm/debug.c
index db9361338b2a..4fd5c216c4bb 100644
--- a/arch/arm64/kvm/debug.c
+++ b/arch/arm64/kvm/debug.c
@@ -105,9 +105,11 @@ static void kvm_arm_setup_mdcr_el2(struct kvm_vcpu *vcpu)
 	 *  - Userspace is using the hardware to debug the guest
 	 *  (KVM_GUESTDBG_USE_HW is set).
 	 *  - The guest is not using debug (KVM_ARM64_DEBUG_DIRTY is clear).
+	 *  - The guest has enabled the OS Lock (debug exceptions are blocked).
 	 */
 	if ((vcpu->guest_debug & KVM_GUESTDBG_USE_HW) ||
-	    !(vcpu->arch.flags & KVM_ARM64_DEBUG_DIRTY))
+	    !(vcpu->arch.flags & KVM_ARM64_DEBUG_DIRTY) ||
+	    kvm_vcpu_os_lock_enabled(vcpu))
 		vcpu->arch.mdcr_el2 |= MDCR_EL2_TDA;
 
 	trace_kvm_arm_set_dreg32("MDCR_EL2", vcpu->arch.mdcr_el2);
@@ -160,8 +162,8 @@ void kvm_arm_setup_debug(struct kvm_vcpu *vcpu)
 
 	kvm_arm_setup_mdcr_el2(vcpu);
 
-	/* Is Guest debugging in effect? */
-	if (vcpu->guest_debug) {
+	/* Check if we need to use the debug registers. */
+	if (vcpu->guest_debug || kvm_vcpu_os_lock_enabled(vcpu)) {
 		/* Save guest debug state */
 		save_guest_debug_regs(vcpu);
 
@@ -223,6 +225,19 @@ void kvm_arm_setup_debug(struct kvm_vcpu *vcpu)
 			trace_kvm_arm_set_regset("WAPTS", get_num_wrps(),
 						&vcpu->arch.debug_ptr->dbg_wcr[0],
 						&vcpu->arch.debug_ptr->dbg_wvr[0]);
+
+		/*
+		 * The OS Lock blocks debug exceptions in all ELs when it is
+		 * enabled. If the guest has enabled the OS Lock, constrain its
+		 * effects to the guest. Emulate the behavior by clearing
+		 * MDSCR_EL1.MDE. In so doing, we ensure that host debug
+		 * exceptions are unaffected by guest configuration of the OS
+		 * Lock.
+		 */
+		} else if (kvm_vcpu_os_lock_enabled(vcpu)) {
+			mdscr = vcpu_read_sys_reg(vcpu, MDSCR_EL1);
+			mdscr &= ~DBG_MDSCR_MDE;
+			vcpu_write_sys_reg(vcpu, mdscr, MDSCR_EL1);
 		}
 	}
 
@@ -244,7 +259,10 @@ void kvm_arm_clear_debug(struct kvm_vcpu *vcpu)
 {
 	trace_kvm_arm_clear_debug(vcpu->guest_debug);
 
-	if (vcpu->guest_debug) {
+	/*
+	 * Restore the guest's debug registers if we were using them.
+	 */
+	if (vcpu->guest_debug || kvm_vcpu_os_lock_enabled(vcpu)) {
 		restore_guest_debug_regs(vcpu);
 
 		/*