Make use of the new vector notifier to track changes of the MSI-X
configuration of virtio PCI devices. On enabling events, we establish
the required virtual IRQ to MSI-X message route and link the signaling
eventfd file descriptor to this vIRQ line. That way, vhost-generated
interrupts can be directly delivered to an in-kernel MSI-X consumer like
the x86 APIC.
Signed-off-by: Jan Kiszka <jan.kiszka@xxxxxxxxxxx>
---
hw/virtio-pci.c | 126 +++++++++++++++++++++++++++++++++++++++++++++++++++++++
hw/virtio-pci.h | 6 +++
2 files changed, 132 insertions(+), 0 deletions(-)
diff --git a/hw/virtio-pci.c b/hw/virtio-pci.c
index 4a4413d..01f5b92 100644
--- a/hw/virtio-pci.c
+++ b/hw/virtio-pci.c
@@ -24,6 +24,7 @@
#include "virtio-scsi.h"
#include "pci.h"
#include "qemu-error.h"
+#include "msi.h"
#include "msix.h"
#include "net.h"
#include "loader.h"
@@ -539,6 +540,107 @@ static void virtio_pci_guest_notifier_read(void *opaque)
}
}
+static int kvm_virtio_pci_vq_vector_use(VirtIOPCIProxy *proxy,
+ unsigned int queue_no,
+ unsigned int vector,
+ MSIMessage msg)
+{
+ VirtQueue *vq = virtio_get_queue(proxy->vdev, queue_no);
+ VirtIOIRQFD *irqfd = &proxy->vector_irqfd[vector];
+ int fd, ret;
+
+ fd = event_notifier_get_fd(virtio_queue_get_guest_notifier(vq));
+
+ if (irqfd->users == 0) {
+ ret = kvm_irqchip_add_msi_route(kvm_state, msg);
+ if (ret < 0) {
+ return ret;
+ }
+ irqfd->virq = ret;
+ }
+ irqfd->users++;
+
+ ret = kvm_irqchip_add_irqfd(kvm_state, fd, irqfd->virq);
+ if (ret < 0) {
+ if (--irqfd->users == 0) {
+ kvm_irqchip_release_virq(kvm_state, irqfd->virq);
+ }
+ return ret;
+ }
+
+ qemu_set_fd_handler(fd, NULL, NULL, NULL);
+
+ return 0;
+}
+
+static void kvm_virtio_pci_vq_vector_release(VirtIOPCIProxy *proxy,
+ unsigned int queue_no,
+ unsigned int vector)
+{
+ VirtQueue *vq = virtio_get_queue(proxy->vdev, queue_no);
+ VirtIOIRQFD *irqfd = &proxy->vector_irqfd[vector];
+ int fd, ret;
+
+ fd = event_notifier_get_fd(virtio_queue_get_guest_notifier(vq));
+
+ ret = kvm_irqchip_remove_irqfd(kvm_state, fd, irqfd->virq);
+ assert(ret == 0);
+
+ if (--irqfd->users == 0) {
+ kvm_irqchip_release_virq(kvm_state, irqfd->virq);
+ }
+
+ qemu_set_fd_handler(fd, virtio_pci_guest_notifier_read, NULL, vq);
+}
+
+static int kvm_virtio_pci_vector_use(PCIDevice *dev, unsigned vector,
+ MSIMessage msg)
+{
+ VirtIOPCIProxy *proxy = container_of(dev, VirtIOPCIProxy, pci_dev);
+ VirtIODevice *vdev = proxy->vdev;
+ int ret, queue_no;
+
+ for (queue_no = 0; queue_no < VIRTIO_PCI_QUEUE_MAX; queue_no++) {
+ if (!virtio_queue_get_num(vdev, queue_no)) {
+ break;
+ }
+ if (virtio_queue_vector(vdev, queue_no) != vector) {
+ continue;
+ }
+ ret = kvm_virtio_pci_vq_vector_use(proxy, queue_no, vector, msg);
+ if (ret < 0) {
+ goto undo;
+ }
+ }
+ return 0;
+
+undo:
+ while (--queue_no >= 0) {
+ if (virtio_queue_vector(vdev, queue_no) != vector) {
+ continue;
+ }
+ kvm_virtio_pci_vq_vector_release(proxy, queue_no, vector);
+ }
+ return ret;
+}
+
+static void kvm_virtio_pci_vector_release(PCIDevice *dev, unsigned vector)
+{
+ VirtIOPCIProxy *proxy = container_of(dev, VirtIOPCIProxy, pci_dev);
+ VirtIODevice *vdev = proxy->vdev;
+ int queue_no;
+
+ for (queue_no = 0; queue_no < VIRTIO_PCI_QUEUE_MAX; queue_no++) {
+ if (!virtio_queue_get_num(vdev, queue_no)) {
+ break;
+ }
+ if (virtio_queue_vector(vdev, queue_no) != vector) {
+ continue;
+ }
+ kvm_virtio_pci_vq_vector_release(proxy, queue_no, vector);
+ }
+}
+
static int virtio_pci_set_guest_notifier(void *opaque, int n, bool assign)
{
VirtIOPCIProxy *proxy = opaque;
@@ -555,6 +657,9 @@ static int virtio_pci_set_guest_notifier(void *opaque, int n, bool assign)
} else {
qemu_set_fd_handler(event_notifier_get_fd(notifier),
NULL, NULL, NULL);
+ /* Test and clear notifier before closing it,
+ * in case poll callback didn't have time to run. */
+ virtio_pci_guest_notifier_read(vq);
event_notifier_cleanup(notifier);
}
@@ -573,6 +678,13 @@ static int virtio_pci_set_guest_notifiers(void *opaque, bool assign)
VirtIODevice *vdev = proxy->vdev;
int r, n;
+ /* Must unset vector notifier while guest notifier is still assigned */
+ if (kvm_irqchip_in_kernel() && !assign) {
+ msix_unset_vector_notifiers(&proxy->pci_dev);
+ g_free(proxy->vector_irqfd);
+ proxy->vector_irqfd = NULL;
+ }
+
for (n = 0; n < VIRTIO_PCI_QUEUE_MAX; n++) {
if (!virtio_queue_get_num(vdev, n)) {
break;
@@ -584,10 +696,24 @@ static int virtio_pci_set_guest_notifiers(void *opaque, bool assign)
}
}
+ /* Must set vector notifier after guest notifier has been assigned */
+ if (kvm_irqchip_in_kernel() && assign) {
+ proxy->vector_irqfd =
+ g_malloc0(sizeof(*proxy->vector_irqfd) *
+ msix_nr_vectors_allocated(&proxy->pci_dev));
+ r = msix_set_vector_notifiers(&proxy->pci_dev,
+ kvm_virtio_pci_vector_use,
+ kvm_virtio_pci_vector_release);
+ if (r < 0) {
+ goto assign_error;
+ }
+ }
+
return 0;
assign_error:
/* We get here on assignment failure. Recover by undoing for VQs 0 .. n. */
+ assert(assign);
while (--n >= 0) {
virtio_pci_set_guest_notifier(opaque, n, !assign);
}
diff --git a/hw/virtio-pci.h b/hw/virtio-pci.h
index e560428..8d28d4b 100644
--- a/hw/virtio-pci.h
+++ b/hw/virtio-pci.h
@@ -25,6 +25,11 @@
#define VIRTIO_PCI_FLAG_USE_IOEVENTFD (1 << VIRTIO_PCI_FLAG_USE_IOEVENTFD_BIT)
typedef struct {
+ int virq;
+ unsigned int users;
+} VirtIOIRQFD;
+
+typedef struct {
PCIDevice pci_dev;
VirtIODevice *vdev;
MemoryRegion bar;
@@ -44,6 +49,7 @@ typedef struct {
VirtIOSCSIConf scsi;
bool ioeventfd_disabled;
bool ioeventfd_started;
+ VirtIOIRQFD *vector_irqfd;
} VirtIOPCIProxy;
void virtio_init_pci(VirtIOPCIProxy *proxy, VirtIODevice *vdev);
--
1.7.3.4
--
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