[PATCH 3/7] kvm tools: Use the new KVM_SIGNAL_MSI ioctl to inject interrupts directly.

[Sasha Levin <levinsasha928@xxxxxxxxx>]

We still create GSIs and keep them for two reasons:

 - They're required by virtio-* devices.
 - There's not much overhead since we just create them when starting the
guest, they don't use anything when the guest is running.

Signed-off-by: Sasha Levin <levinsasha928@xxxxxxxxx>
---
 tools/kvm/include/kvm/virtio-pci.h |  3 +++
 tools/kvm/virtio/pci.c             | 25 +++++++++++++++++++++++--
 2 files changed, 26 insertions(+), 2 deletions(-)

diff --git a/tools/kvm/include/kvm/virtio-pci.h b/tools/kvm/include/kvm/virtio-pci.h
index 9e036b2..44130e0c 100644
--- a/tools/kvm/include/kvm/virtio-pci.h
+++ b/tools/kvm/include/kvm/virtio-pci.h
@@ -15,6 +15,8 @@ struct virtio_pci_ioevent_param {
 	u32			vq;
 };
 
+#define VIRTIO_PCI_F_SIGNAL_MSI (1 << 0)
+
 struct virtio_pci {
 	struct pci_device_header pci_hdr;
 	void			*dev;
@@ -22,6 +24,7 @@ struct virtio_pci {
 	u16			base_addr;
 	u8			status;
 	u8			isr;
+	u32			features;
 
 	/* MSI-X */
 	u16			config_vector;
diff --git a/tools/kvm/virtio/pci.c b/tools/kvm/virtio/pci.c
index f17cd8a..4dc7916 100644
--- a/tools/kvm/virtio/pci.c
+++ b/tools/kvm/virtio/pci.c
@@ -7,6 +7,7 @@
 #include "kvm/virtio.h"
 #include "kvm/ioeventfd.h"
 
+#include <sys/ioctl.h>
 #include <linux/virtio_pci.h>
 #include <linux/byteorder.h>
 #include <string.h>
@@ -236,6 +237,17 @@ static void virtio_pci__mmio_callback(u64 addr, u8 *data, u32 len, u8 is_write,
 		memcpy(data, table + addr - offset, len);
 }
 
+static void virtio_pci__signal_msi(struct kvm *kvm, struct virtio_pci *vpci, int vec)
+{
+	struct kvm_msi msi = {
+		.address_lo = vpci->msix_table[vec].msg.address_lo,
+		.address_hi = vpci->msix_table[vec].msg.address_hi,
+		.data = vpci->msix_table[vec].msg.data,
+	};
+
+	ioctl(kvm->vm_fd, KVM_SIGNAL_MSI, &msi);
+}
+
 int virtio_pci__signal_vq(struct kvm *kvm, struct virtio_device *vdev, u32 vq)
 {
 	struct virtio_pci *vpci = vdev->virtio;
@@ -249,7 +261,10 @@ int virtio_pci__signal_vq(struct kvm *kvm, struct virtio_device *vdev, u32 vq)
 			return 0;
 		}
 
-		kvm__irq_trigger(kvm, vpci->gsis[vq]);
+		if (vpci->features & VIRTIO_PCI_F_SIGNAL_MSI)
+			virtio_pci__signal_msi(kvm, vpci, vpci->vq_vector[vq]);
+		else
+			kvm__irq_trigger(kvm, vpci->gsis[vq]);
 	} else {
 		vpci->isr = VIRTIO_IRQ_HIGH;
 		kvm__irq_trigger(kvm, vpci->pci_hdr.irq_line);
@@ -270,7 +285,10 @@ int virtio_pci__signal_config(struct kvm *kvm, struct virtio_device *vdev)
 			return 0;
 		}
 
-		kvm__irq_trigger(kvm, vpci->config_gsi);
+		if (vpci->features & VIRTIO_PCI_F_SIGNAL_MSI)
+			virtio_pci__signal_msi(kvm, vpci, vpci->vq_vector[vpci->config_vector]);
+		else
+			kvm__irq_trigger(kvm, vpci->config_gsi);
 	} else {
 		vpci->isr = VIRTIO_PCI_ISR_CONFIG;
 		kvm__irq_trigger(kvm, vpci->pci_hdr.irq_line);
@@ -347,6 +365,9 @@ int virtio_pci__init(struct kvm *kvm, void *dev, struct virtio_device *vdev,
 	if (r < 0)
 		goto free_mmio;
 
+	if (kvm__supports_extension(kvm, KVM_CAP_SIGNAL_MSI))
+		vpci->features |= VIRTIO_PCI_F_SIGNAL_MSI;
+
 	vpci->pci_hdr.irq_pin	= pin;
 	vpci->pci_hdr.irq_line	= line;
 	r = pci__register(&vpci->pci_hdr, ndev);
-- 
1.7.12

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