[PATCH kvmtool v2 4/7] arm64: Initialise the PMU after the GIC

[Alexandru Elisei]

PMU initialisation is done in:

setup_fdt()
  vcpu->generate_fdt_nodes()
    pmu__generate_fdt_nodes()

The PMU ioctl KVM_ARM_VCPU_PMU_V3_INIT requires that the GIC has been
initialised, which is done in gic__init_gic().

gic__init_gic() and setup_fdt() are part of the same initialisation list.
The relative order on the list depends on the order of compilation: gic.c
is compiled after fdt.c and this places gic__init_gic() first on the
initialisation list.

If the compilation order changes and gic.c is compiled *before* fdt.c,
gic__init_gic() will be executed *after* setup_fdt() and PMU initialisation
will fail with an error message:

PMU KVM_SET_DEVICE_ATTR: No such device

This is fragile and hard to debug. Improve the situation by having
gic__init_gic() explicitely initialize the PMU.

Signed-off-by: Alexandru Elisei <alexandru.elisei at arm.com>
---
 arm64/gic.c             |  9 ++++++++-
 arm64/include/asm/pmu.h |  3 +++
 arm64/pmu.c             | 28 ++++++++++++++++++----------
 3 files changed, 29 insertions(+), 11 deletions(-)

diff --git a/arm64/gic.c b/arm64/gic.c
index b0be9e5766df..1e4009625595 100644
--- a/arm64/gic.c
+++ b/arm64/gic.c
@@ -9,6 +9,8 @@
 #include <linux/kvm.h>
 #include <linux/sizes.h>
 
+#include <asm/pmu.h>
+
 #define IRQCHIP_GIC 0
 
 #define GIC_MAINT_IRQ	9
@@ -355,7 +357,12 @@ static int gic__init_gic(struct kvm *kvm)
 
 	vgic_is_init = true;
 
-	return irq__setup_irqfd_lines(kvm);
+	ret = irq__setup_irqfd_lines(kvm);
+	if (ret)
+		return ret;
+
+	/* The PMU requires that the GIC has been initialized. */
+	return pmu__init(kvm);
 }
 late_init(gic__init_gic)
 
diff --git a/arm64/include/asm/pmu.h b/arm64/include/asm/pmu.h
index 38e3154b11b7..74566943f355 100644
--- a/arm64/include/asm/pmu.h
+++ b/arm64/include/asm/pmu.h
@@ -3,6 +3,9 @@
 
 #define KVM_ARM_PMUv3_PPI			23
 
+struct kvm;
+
 void pmu__generate_fdt_nodes(void *fdt, struct kvm *kvm);
+int pmu__init(struct kvm *kvm);
 
 #endif /* __ARM_PMU_H__ */
diff --git a/arm64/pmu.c b/arm64/pmu.c
index 5f31d6b6f346..92cacd62479e 100644
--- a/arm64/pmu.c
+++ b/arm64/pmu.c
@@ -193,21 +193,32 @@ static int find_pmu(struct kvm *kvm)
 void pmu__generate_fdt_nodes(void *fdt, struct kvm *kvm)
 {
 	const char compatible[] = "arm,armv8-pmuv3";
-	int irq = KVM_ARM_PMUv3_PPI;
-	struct kvm_cpu *vcpu;
-	int pmu_id = -ENXIO;
-	int i;
-
 	u32 cpu_mask = gic__get_fdt_irq_cpumask(kvm);
 	u32 irq_prop[] = {
 		cpu_to_fdt32(GIC_FDT_IRQ_TYPE_PPI),
-		cpu_to_fdt32(irq - 16),
+		cpu_to_fdt32(KVM_ARM_PMUv3_PPI - 16),
 		cpu_to_fdt32(cpu_mask | IRQ_TYPE_LEVEL_HIGH),
 	};
 
 	if (!kvm->cfg.arch.has_pmuv3)
 		return;
 
+	_FDT(fdt_begin_node(fdt, "pmu"));
+	_FDT(fdt_property(fdt, "compatible", compatible, sizeof(compatible)));
+	_FDT(fdt_property(fdt, "interrupts", irq_prop, sizeof(irq_prop)));
+	_FDT(fdt_end_node(fdt));
+}
+
+int pmu__init(struct kvm *kvm)
+{
+	int irq = KVM_ARM_PMUv3_PPI;
+	struct kvm_cpu *vcpu;
+	int pmu_id = -ENXIO;
+	int i;
+
+	if (!kvm->cfg.arch.has_pmuv3)
+		return 0;
+
 	if (pmu_has_attr(kvm->cpus[0], KVM_ARM_VCPU_PMU_V3_SET_PMU)) {
 		pmu_id = find_pmu(kvm);
 		if (pmu_id < 0) {
@@ -228,8 +239,5 @@ void pmu__generate_fdt_nodes(void *fdt, struct kvm *kvm)
 		set_pmu_attr(vcpu, NULL, KVM_ARM_VCPU_PMU_V3_INIT);
 	}
 
-	_FDT(fdt_begin_node(fdt, "pmu"));
-	_FDT(fdt_property(fdt, "compatible", compatible, sizeof(compatible)));
-	_FDT(fdt_property(fdt, "interrupts", irq_prop, sizeof(irq_prop)));
-	_FDT(fdt_end_node(fdt));
+	return 0;
 }
-- 
2.54.0