Re: [PATCH 24/37] KVM: PPC: booke: rework rescheduling checks

On 27.02.2012, at 20:28, Scott Wood wrote:

On 02/24/2012 08:26 AM, Alexander Graf wrote:

quoted

-void kvmppc_core_prepare_to_enter(struct kvm_vcpu *vcpu)
+int kvmppc_core_prepare_to_enter(struct kvm_vcpu *vcpu)
{
	unsigned long *pending =3D &vcpu->arch.pending_exceptions;
	unsigned long old_pending =3D vcpu->arch.pending_exceptions;

@@ -283,6 +283,8 @@ void kvmppc_core_prepare_to_enter(struct kvm_vcpu =

*vcpu)

quoted

=20
	/* Tell the guest about our interrupt status */
	kvmppc_update_int_pending(vcpu, *pending, old_pending);
+
+	return 0;
}
=20
pfn_t kvmppc_gfn_to_pfn(struct kvm_vcpu *vcpu, gfn_t gfn)

diff --git a/arch/powerpc/kvm/booke.c b/arch/powerpc/kvm/booke.c
index 9979be1..3fcec2c 100644
--- a/arch/powerpc/kvm/booke.c
+++ b/arch/powerpc/kvm/booke.c

@@ -439,8 +439,9 @@ static void kvmppc_core_check_exceptions(struct =

kvm_vcpu *vcpu)

quoted

}
=20
/* Check pending exceptions and deliver one, if possible. */
-void kvmppc_core_prepare_to_enter(struct kvm_vcpu *vcpu)
+int kvmppc_core_prepare_to_enter(struct kvm_vcpu *vcpu)
{
+	int r =3D 0;
	WARN_ON_ONCE(!irqs_disabled());
=20
	kvmppc_core_check_exceptions(vcpu);

@@ -451,8 +452,44 @@ void kvmppc_core_prepare_to_enter(struct =

kvm_vcpu *vcpu)

quoted

		local_irq_disable();
=20
		kvmppc_set_exit_type(vcpu, EMULATED_MTMSRWE_EXITS);
-		kvmppc_core_check_exceptions(vcpu);
+		r =3D 1;
	};
+
+	return r;
+}
+
+/*
+ * Common checks before entering the guest world.  Call with =

interrupts

quoted

+ * disabled.
+ *
+ * returns !0 if a signal is pending and check_signal is true
+ */
+static int kvmppc_prepare_to_enter(struct kvm_vcpu *vcpu, bool =

check_signal)

quoted

+{
+	int r =3D 0;
+
+	WARN_ON_ONCE(!irqs_disabled());
+	while (true) {
+		if (need_resched()) {
+			local_irq_enable();
+			cond_resched();
+			local_irq_disable();
+			continue;
+		}
+
+		if (kvmppc_core_prepare_to_enter(vcpu)) {
+			/* interrupts got enabled in between, so we
+			   are back at square 1 */
+			continue;
+		}
+
+
+		if (check_signal && signal_pending(current))
+			r =3D 1;

=20
If there is a signal pending and MSR[WE] is set, we'll loop forever
without reaching this check.

Good point. How about something like this on top (will fold in later)?

diff --git a/arch/powerpc/kvm/booke.c b/arch/powerpc/kvm/booke.c
index 430055e..9f27258 100644
--- a/arch/powerpc/kvm/booke.c
+++ b/arch/powerpc/kvm/booke.c

@@ -477,15 +477,17 @@ static int kvmppc_prepare_to_enter(struct kvm_vcpu =

*vcpu)
                        continue;
                }
=20
+               if (signal_pending(current)) {
+                       r =3D 1;
+                       break;
+               }
+
                if (kvmppc_core_prepare_to_enter(vcpu)) {
                        /* interrupts got enabled in between, so we
                           are back at square 1 */
                        continue;
                }
=20
-               if (signal_pending(current))
-                       r =3D 1;
-
                break;
        }
=20

Alex