[PATCH v9 1/2] kvm: Use a reserved IRQ source ID for irqfd

[Alex Williamson <alex.williamson@xxxxxxxxxx>]

KVM_IRQFD currently uses the reserved KVM_USERSPACE_IRQ_SOURCE_ID
which is also shared with userspace injection methods like
KVM_IRQ_LINE.  This can cause a conflict if an irqfd triggers on
a GSI asserted through KVM_IRQ_LINE.  Move irqfd to it's own
reserved IRQ source ID.  Add a capability for userspace to test
for this fix.

Signed-off-by: Alex Williamson <alex.williamson@xxxxxxxxxx>
---

 arch/x86/kvm/x86.c       |    3 +++
 include/linux/kvm.h      |    1 +
 include/linux/kvm_host.h |    1 +
 virt/kvm/eventfd.c       |    6 +++---
 4 files changed, 8 insertions(+), 3 deletions(-)

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 42bce48..cd98673 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -2174,6 +2174,7 @@ int kvm_dev_ioctl_check_extension(long ext)
 	case KVM_CAP_GET_TSC_KHZ:
 	case KVM_CAP_PCI_2_3:
 	case KVM_CAP_KVMCLOCK_CTRL:
+	case KVM_CAP_IRQFD_IRQ_SOURCE_ID:
 		r = 1;
 		break;
 	case KVM_CAP_COALESCED_MMIO:
@@ -6258,6 +6259,8 @@ int kvm_arch_init_vm(struct kvm *kvm, unsigned long type)
 
 	/* Reserve bit 0 of irq_sources_bitmap for userspace irq source */
 	set_bit(KVM_USERSPACE_IRQ_SOURCE_ID, &kvm->arch.irq_sources_bitmap);
+	/* Reserve bit 1 of irq_sources_bitmap for irqfd irq source */
+	set_bit(KVM_IRQFD_IRQ_SOURCE_ID, &kvm->arch.irq_sources_bitmap);
 
 	raw_spin_lock_init(&kvm->arch.tsc_write_lock);
 
diff --git a/include/linux/kvm.h b/include/linux/kvm.h
index 2ce09aa..ae66b9c 100644
--- a/include/linux/kvm.h
+++ b/include/linux/kvm.h
@@ -618,6 +618,7 @@ struct kvm_ppc_smmu_info {
 #define KVM_CAP_PPC_GET_SMMU_INFO 78
 #define KVM_CAP_S390_COW 79
 #define KVM_CAP_PPC_ALLOC_HTAB 80
+#define KVM_CAP_IRQFD_IRQ_SOURCE_ID 81
 
 #ifdef KVM_CAP_IRQ_ROUTING
 
diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
index b70b48b..b763230 100644
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -71,6 +71,7 @@
 #define KVM_REQ_PMI               17
 
 #define KVM_USERSPACE_IRQ_SOURCE_ID	0
+#define KVM_IRQFD_IRQ_SOURCE_ID		1
 
 struct kvm;
 struct kvm_vcpu;
diff --git a/virt/kvm/eventfd.c b/virt/kvm/eventfd.c
index 7d7e2aa..2245cfa 100644
--- a/virt/kvm/eventfd.c
+++ b/virt/kvm/eventfd.c
@@ -67,8 +67,8 @@ irqfd_inject(struct work_struct *work)
 	struct _irqfd *irqfd = container_of(work, struct _irqfd, inject);
 	struct kvm *kvm = irqfd->kvm;
 
-	kvm_set_irq(kvm, KVM_USERSPACE_IRQ_SOURCE_ID, irqfd->gsi, 1);
-	kvm_set_irq(kvm, KVM_USERSPACE_IRQ_SOURCE_ID, irqfd->gsi, 0);
+	kvm_set_irq(kvm, KVM_IRQFD_IRQ_SOURCE_ID, irqfd->gsi, 1);
+	kvm_set_irq(kvm, KVM_IRQFD_IRQ_SOURCE_ID, irqfd->gsi, 0);
 }
 
 /*
@@ -138,7 +138,7 @@ irqfd_wakeup(wait_queue_t *wait, unsigned mode, int sync, void *key)
 		irq = rcu_dereference(irqfd->irq_entry);
 		/* An event has been signaled, inject an interrupt */
 		if (irq)
-			kvm_set_msi(irq, kvm, KVM_USERSPACE_IRQ_SOURCE_ID, 1);
+			kvm_set_msi(irq, kvm, KVM_IRQFD_IRQ_SOURCE_ID, 1);
 		else
 			schedule_work(&irqfd->inject);
 		rcu_read_unlock();

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