[RFC PATCH 08/13] KVM: arm64: Make per-vCPU vLPI control ioctls atomic

[Maximilian Dittgen <mdittgen@amazon.de>]

Per-vCPU vLPI enable, disable, and query ioctls should finish
reading or writing the state of their target vCPU before
another operation does the same.

Implement a vlpi_toggle_mutex to be acquired whenever
KVM_ENABLE_VCPU_VLPI, KVM_DISABLE_VCPU_VLPI, or
KVM_QUERY_VCPU_VLPI ioctls are handled.

Signed-off-by: Maximilian Dittgen <mdittgen@amazon.com>
---
 arch/arm64/kvm/arm.c          | 3 +++
 arch/arm64/kvm/vgic/vgic-v4.c | 5 +++++
 include/kvm/arm_vgic.h        | 3 +++
 3 files changed, 11 insertions(+)

diff --git a/arch/arm64/kvm/arm.c b/arch/arm64/kvm/arm.c
index 180eaa4165e9..c2224664f05e 100644
--- a/arch/arm64/kvm/arm.c
+++ b/arch/arm64/kvm/arm.c
@@ -1961,6 +1961,7 @@ int kvm_arch_vm_ioctl(struct file *filp, unsigned int ioctl, unsigned long arg)
 		if (!vcpu)
 			return -EINVAL;
 
+		guard(mutex)(&vcpu->arch.vgic_cpu.vlpi_toggle_mutex);
 		return kvm_vgic_enable_vcpu_vlpi(vcpu);
 	}
 	case KVM_DISABLE_VCPU_VLPI: {
@@ -1974,6 +1975,7 @@ int kvm_arch_vm_ioctl(struct file *filp, unsigned int ioctl, unsigned long arg)
 		if (!vcpu)
 			return -EINVAL;
 
+		guard(mutex)(&vcpu->arch.vgic_cpu.vlpi_toggle_mutex);
 		return kvm_vgic_disable_vcpu_vlpi(vcpu);
 	}
 	case KVM_QUERY_VCPU_VLPI: {
@@ -1987,6 +1989,7 @@ int kvm_arch_vm_ioctl(struct file *filp, unsigned int ioctl, unsigned long arg)
 		if (!vcpu)
 			return -EINVAL;
 
+		guard(mutex)(&vcpu->arch.vgic_cpu.vlpi_toggle_mutex);
 		return kvm_vgic_query_vcpu_vlpi(vcpu);
 	}
 	default:
diff --git a/arch/arm64/kvm/vgic/vgic-v4.c b/arch/arm64/kvm/vgic/vgic-v4.c
index 39fababf2861..b7dbc1789c90 100644
--- a/arch/arm64/kvm/vgic/vgic-v4.c
+++ b/arch/arm64/kvm/vgic/vgic-v4.c
@@ -325,6 +325,11 @@ int vgic_v4_init(struct kvm *kvm)
 		if (!dist->its_vm.vprop_page)
 			ret = -ENOMEM;
 	}
+
+	/* vLPI toggle mutex */
+	kvm_for_each_vcpu(i, vcpu, kvm)
+		mutex_init(&vcpu->arch.vgic_cpu.vlpi_toggle_mutex);
+
 #endif
 	if (ret)
 		vgic_v4_teardown(kvm);
diff --git a/include/kvm/arm_vgic.h b/include/kvm/arm_vgic.h
index 18a49c4b83f8..c9dad0e84c77 100644
--- a/include/kvm/arm_vgic.h
+++ b/include/kvm/arm_vgic.h
@@ -372,6 +372,9 @@ struct vgic_cpu {
 	u32 rdreg_index;
 	atomic_t syncr_busy;
 
+	/* Ensure atomicity of per-vCPU vLPI enable/disable/query operations */
+	struct mutex vlpi_toggle_mutex;
+
 	/* Contains the attributes and gpa of the LPI pending tables. */
 	u64 pendbaser;
 	/* GICR_CTLR.{ENABLE_LPIS,RWP} */
-- 
2.50.1 (Apple Git-155)




Amazon Web Services Development Center Germany GmbH
Tamara-Danz-Str. 13
10243 Berlin
Geschaeftsfuehrung: Christian Schlaeger, Christof Hellmis
Eingetragen am Amtsgericht Charlottenburg unter HRB 257764 B
Sitz: Berlin
Ust-ID: DE 365 538 597