KVM: ppc: guest breakpoint support

Allow host userspace to program hardware debug registers to set breakpoints
inside guests.

Signed-off-by: Jerone Young <jyoung5@us.ibm.com>
Signed-off-by: Hollis Blanchard <hollisb@us.ibm.com>
Signed-off-by: Avi Kivity <avi@qumranet.com>

1 files changed, 83 insertions, 1 deletions

diff --git a/arch/powerpc/kvm/powerpc.c b/arch/powerpc/kvm/powerpc.c
index 53826a5..b756071 100644
--- a/arch/powerpc/kvm/powerpc.c
+++ b/arch/powerpc/kvm/powerpc.c
@@ -239,18 +239,100 @@ void kvm_arch_vcpu_uninit(struct kvm_vcpu *vcpu)
 {
 }
 
+/* Note: clearing MSR[DE] just means that the debug interrupt will not be
+ * delivered *immediately*. Instead, it simply sets the appropriate DBSR bits.
+ * If those DBSR bits are still set when MSR[DE] is re-enabled, the interrupt
+ * will be delivered as an "imprecise debug event" (which is indicated by
+ * DBSR[IDE].
+ */
+static void kvmppc_disable_debug_interrupts(void)
+{
+	mtmsr(mfmsr() & ~MSR_DE);
+}
+
+static void kvmppc_restore_host_debug_state(struct kvm_vcpu *vcpu)
+{
+	kvmppc_disable_debug_interrupts();
+
+	mtspr(SPRN_IAC1, vcpu->arch.host_iac[0]);
+	mtspr(SPRN_IAC2, vcpu->arch.host_iac[1]);
+	mtspr(SPRN_IAC3, vcpu->arch.host_iac[2]);
+	mtspr(SPRN_IAC4, vcpu->arch.host_iac[3]);
+	mtspr(SPRN_DBCR1, vcpu->arch.host_dbcr1);
+	mtspr(SPRN_DBCR2, vcpu->arch.host_dbcr2);
+	mtspr(SPRN_DBCR0, vcpu->arch.host_dbcr0);
+	mtmsr(vcpu->arch.host_msr);
+}
+
+static void kvmppc_load_guest_debug_registers(struct kvm_vcpu *vcpu)
+{
+	struct kvm_guest_debug *dbg = &vcpu->guest_debug;
+	u32 dbcr0 = 0;
+
+	vcpu->arch.host_msr = mfmsr();
+	kvmppc_disable_debug_interrupts();
+
+	/* Save host debug register state. */
+	vcpu->arch.host_iac[0] = mfspr(SPRN_IAC1);
+	vcpu->arch.host_iac[1] = mfspr(SPRN_IAC2);
+	vcpu->arch.host_iac[2] = mfspr(SPRN_IAC3);
+	vcpu->arch.host_iac[3] = mfspr(SPRN_IAC4);
+	vcpu->arch.host_dbcr0 = mfspr(SPRN_DBCR0);
+	vcpu->arch.host_dbcr1 = mfspr(SPRN_DBCR1);
+	vcpu->arch.host_dbcr2 = mfspr(SPRN_DBCR2);
+
+	/* set registers up for guest */
+
+	if (dbg->bp[0]) {
+		mtspr(SPRN_IAC1, dbg->bp[0]);
+		dbcr0 |= DBCR0_IAC1 | DBCR0_IDM;
+	}
+	if (dbg->bp[1]) {
+		mtspr(SPRN_IAC2, dbg->bp[1]);
+		dbcr0 |= DBCR0_IAC2 | DBCR0_IDM;
+	}
+	if (dbg->bp[2]) {
+		mtspr(SPRN_IAC3, dbg->bp[2]);
+		dbcr0 |= DBCR0_IAC3 | DBCR0_IDM;
+	}
+	if (dbg->bp[3]) {
+		mtspr(SPRN_IAC4, dbg->bp[3]);
+		dbcr0 |= DBCR0_IAC4 | DBCR0_IDM;
+	}
+
+	mtspr(SPRN_DBCR0, dbcr0);
+	mtspr(SPRN_DBCR1, 0);
+	mtspr(SPRN_DBCR2, 0);
+}
+
 void kvm_arch_vcpu_load(struct kvm_vcpu *vcpu, int cpu)
 {
+	if (vcpu->guest_debug.enabled)
+		kvmppc_load_guest_debug_registers(vcpu);
 }
 
 void kvm_arch_vcpu_put(struct kvm_vcpu *vcpu)
 {
+	if (vcpu->guest_debug.enabled)
+		kvmppc_restore_host_debug_state(vcpu);
 }
 
 int kvm_arch_vcpu_ioctl_debug_guest(struct kvm_vcpu *vcpu,
                                     struct kvm_debug_guest *dbg)
 {
-	return -ENOTSUPP;
+	int i;
+
+	vcpu->guest_debug.enabled = dbg->enabled;
+	if (vcpu->guest_debug.enabled) {
+		for (i=0; i < ARRAY_SIZE(vcpu->guest_debug.bp); i++) {
+			if (dbg->breakpoints[i].enabled)
+				vcpu->guest_debug.bp[i] = dbg->breakpoints[i].address;
+			else
+				vcpu->guest_debug.bp[i] = 0;
+		}
+	}
+
+	return 0;
 }
 
 static void kvmppc_complete_dcr_load(struct kvm_vcpu *vcpu,