KVM: arm64: enable KVM_CAP_SET_GUEST_DEBUG

Finally advertise the KVM capability for SET_GUEST_DEBUG. Once arm
support is added this check can be moved to the common
kvm_vm_ioctl_check_extension() code.

Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
Acked-by: Christoffer Dall <christoffer.dall@linaro.org>
Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>

1 files changed, 35 insertions, 5 deletions

diff --git a/arch/arm64/kvm/debug.c b/arch/arm64/kvm/debug.c
index e0947b77faaa..4a99e54d7f3d 100644
--- a/arch/arm64/kvm/debug.c
+++ b/arch/arm64/kvm/debug.c
@@ -105,10 +105,6 @@ void kvm_arm_setup_debug(struct kvm_vcpu *vcpu)
 				MDCR_EL2_TDRA |
 				MDCR_EL2_TDOSA);
 
-	/* Trap on access to debug registers? */
-	if (trap_debug)
-		vcpu->arch.mdcr_el2 |= MDCR_EL2_TDA;
-
 	/* Is Guest debugging in effect? */
 	if (vcpu->guest_debug) {
 		/* Route all software debug exceptions to EL2 */
@@ -143,11 +139,45 @@ void kvm_arm_setup_debug(struct kvm_vcpu *vcpu)
 		} else {
 			vcpu_sys_reg(vcpu, MDSCR_EL1) &= ~DBG_MDSCR_SS;
 		}
+
+		/*
+		 * HW Breakpoints and watchpoints
+		 *
+		 * We simply switch the debug_ptr to point to our new
+		 * external_debug_state which has been populated by the
+		 * debug ioctl. The existing KVM_ARM64_DEBUG_DIRTY
+		 * mechanism ensures the registers are updated on the
+		 * world switch.
+		 */
+		if (vcpu->guest_debug & KVM_GUESTDBG_USE_HW) {
+			/* Enable breakpoints/watchpoints */
+			vcpu_sys_reg(vcpu, MDSCR_EL1) |= DBG_MDSCR_MDE;
+
+			vcpu->arch.debug_ptr = &vcpu->arch.external_debug_state;
+			vcpu->arch.debug_flags |= KVM_ARM64_DEBUG_DIRTY;
+			trap_debug = true;
+		}
 	}
+
+	BUG_ON(!vcpu->guest_debug &&
+		vcpu->arch.debug_ptr != &vcpu->arch.vcpu_debug_state);
+
+	/* Trap debug register access */
+	if (trap_debug)
+		vcpu->arch.mdcr_el2 |= MDCR_EL2_TDA;
 }
 
 void kvm_arm_clear_debug(struct kvm_vcpu *vcpu)
 {
-	if (vcpu->guest_debug)
+	if (vcpu->guest_debug) {
 		restore_guest_debug_regs(vcpu);
+
+		/*
+		 * If we were using HW debug we need to restore the
+		 * debug_ptr to the guest debug state.
+		 */
+		if (vcpu->guest_debug & KVM_GUESTDBG_USE_HW)
+			kvm_arm_reset_debug_ptr(vcpu);
+
+	}
 }