[RFC PATCH v4 16/39] KVM: arm64: Make SPE available when at least one CPU supports it

[Alexandru Elisei]

KVM SPE emulation requires at least one physical CPU to support SPE.
Initialize the cpumask of PEs that support SPE the first time
KVM_CAP_ARM_SPE is queried or when the first virtual machine is created,
whichever comes first.

Signed-off-by: Alexandru Elisei <alexandru.elisei at arm.com>
---
 arch/arm64/include/asm/kvm_spe.h | 26 ++++++++++++++++++++++++++
 arch/arm64/kvm/Makefile          |  1 +
 arch/arm64/kvm/arm.c             |  4 ++++
 arch/arm64/kvm/spe.c             | 32 ++++++++++++++++++++++++++++++++
 4 files changed, 63 insertions(+)
 create mode 100644 arch/arm64/include/asm/kvm_spe.h
 create mode 100644 arch/arm64/kvm/spe.c

diff --git a/arch/arm64/include/asm/kvm_spe.h b/arch/arm64/include/asm/kvm_spe.h
new file mode 100644
index 000000000000..328115ce0b48
--- /dev/null
+++ b/arch/arm64/include/asm/kvm_spe.h
@@ -0,0 +1,26 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ * Copyright (C) 2021 - ARM Ltd
+ */
+
+#ifndef __ARM64_KVM_SPE_H__
+#define __ARM64_KVM_SPE_H__
+
+#ifdef CONFIG_KVM_ARM_SPE
+DECLARE_STATIC_KEY_FALSE(kvm_spe_available);
+
+static __always_inline bool kvm_supports_spe(void)
+{
+	return static_branch_likely(&kvm_spe_available);
+}
+
+void kvm_spe_init_supported_cpus(void);
+void kvm_spe_vm_init(struct kvm *kvm);
+#else
+#define kvm_supports_spe()	(false)
+
+static inline void kvm_spe_init_supported_cpus(void) {}
+static inline void kvm_spe_vm_init(struct kvm *kvm) {}
+#endif /* CONFIG_KVM_ARM_SPE */
+
+#endif /* __ARM64_KVM_SPE_H__ */
diff --git a/arch/arm64/kvm/Makefile b/arch/arm64/kvm/Makefile
index 989bb5dad2c8..86092a0f8367 100644
--- a/arch/arm64/kvm/Makefile
+++ b/arch/arm64/kvm/Makefile
@@ -25,3 +25,4 @@ kvm-y := $(KVM)/kvm_main.o $(KVM)/coalesced_mmio.o $(KVM)/eventfd.o \
 	 vgic/vgic-its.o vgic/vgic-debug.o
 
 kvm-$(CONFIG_HW_PERF_EVENTS)  += pmu-emul.o
+kvm-$(CONFIG_KVM_ARM_SPE)     += spe.o
diff --git a/arch/arm64/kvm/arm.c b/arch/arm64/kvm/arm.c
index 22544eb367f3..82cb7b5b3b45 100644
--- a/arch/arm64/kvm/arm.c
+++ b/arch/arm64/kvm/arm.c
@@ -35,6 +35,7 @@
 #include <asm/kvm_arm.h>
 #include <asm/kvm_asm.h>
 #include <asm/kvm_mmu.h>
+#include <asm/kvm_spe.h>
 #include <asm/kvm_emulate.h>
 #include <asm/sections.h>
 
@@ -180,6 +181,8 @@ int kvm_arch_init_vm(struct kvm *kvm, unsigned long type)
 
 	set_default_spectre(kvm);
 
+	kvm_spe_vm_init(kvm);
+
 	return ret;
 out_free_stage2_pgd:
 	kvm_free_stage2_pgd(&kvm->arch.mmu);
@@ -305,6 +308,7 @@ int kvm_vm_ioctl_check_extension(struct kvm *kvm, long ext)
 		r = 1;
 		break;
 	case KVM_CAP_ARM_SPE:
+		kvm_spe_init_supported_cpus();
 		r = 0;
 		break;
 	default:
diff --git a/arch/arm64/kvm/spe.c b/arch/arm64/kvm/spe.c
new file mode 100644
index 000000000000..83f92245f881
--- /dev/null
+++ b/arch/arm64/kvm/spe.c
@@ -0,0 +1,32 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright (C) 2021 - ARM Ltd
+ */
+
+#include <linux/cpumask.h>
+#include <linux/kvm_host.h>
+#include <linux/perf/arm_pmu.h>
+
+#include <asm/kvm_spe.h>
+
+DEFINE_STATIC_KEY_FALSE(kvm_spe_available);
+
+static const cpumask_t *supported_cpus;
+
+void kvm_spe_init_supported_cpus(void)
+{
+	if (likely(supported_cpus))
+		return;
+
+	supported_cpus = arm_spe_pmu_supported_cpus();
+	BUG_ON(!supported_cpus);
+
+	if (!cpumask_empty(supported_cpus))
+		static_branch_enable(&kvm_spe_available);
+}
+
+void kvm_spe_vm_init(struct kvm *kvm)
+{
+	/* Set supported_cpus if it isn't already initialized. */
+	kvm_spe_init_supported_cpus();
+}
-- 
2.33.0