From 81ee28858d0082b300184c9fcfc10480c67aa74d Mon Sep 17 00:00:00 2001
From: Alex Williamson <alex.williamson@redhat.com>
Date: Thu, 7 Aug 2014 21:03:08 +0200
Subject: [PATCH 5/7] vfio-pci: Fix MSI-X masking performance
Message-id: <20140807210308.11689.93757.stgit@gimli.home>
Patchwork-id: 60481
O-Subject: [RHEL7.0/z qemu-kvm PATCH v2 4/6] vfio-pci: Fix MSI-X masking performance
Bugzilla: 1098976
RH-Acked-by: Bandan Das <bsd@redhat.com>
RH-Acked-by: Amos Kong <akong@redhat.com>
RH-Acked-by: Laszlo Ersek <lersek@redhat.com>
There are still old guests out there that over-exercise MSI-X masking.
The current code completely sets-up and tears-down an MSI-X vector on
the "use" and "release" callbacks. While this is functional, it can
slow an old guest to a crawl. We can easily skip the KVM parts of
this so that we keep the MSI route and irqfd setup. We do however
need to switch VFIO to trigger a different eventfd while masked.
Actually, we have the option of continuing to use -1 to disable the
trigger, but by using another EventNotifier we can allow the MSI-X
core to emulate pending bits and re-fire the vector once unmasked.
MSI code gets updated as well to use the same setup and teardown
structures and functions.
Prior to this change, an igbvf assigned to a RHEL5 guest gets about
20Mbps and 50 transactions/s with netperf (remote or VF->PF). With
this change, we get line rate and 3k transactions/s remote or 2Gbps
and 6k+ transactions/s to the PF. No significant change is expected
for newer guests with more well behaved MSI-X support.
Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
Signed-off-by: Miroslav Rezanina <mrezanin@redhat.com>
---
hw/misc/vfio.c | 233 ++++++++++++++++++++++++++++++++-------------------------
1 file changed, 131 insertions(+), 102 deletions(-)
diff --git a/hw/misc/vfio.c b/hw/misc/vfio.c
index 5f0460a..bd37924 100644
--- a/hw/misc/vfio.c
+++ b/hw/misc/vfio.c
@@ -120,6 +120,7 @@ typedef struct VFIOINTx {
typedef struct VFIOMSIVector {
EventNotifier interrupt; /* eventfd triggered on interrupt */
+ EventNotifier kvm_interrupt; /* eventfd triggered for KVM irqfd bypass */
struct VFIODevice *vdev; /* back pointer to device */
MSIMessage msg; /* cache the MSI message so we know when it changes */
int virq; /* KVM irqchip route for QEMU bypass */
@@ -663,10 +664,11 @@ static int vfio_enable_vectors(VFIODevice *vdev, bool msix)
for (i = 0; i < vdev->nr_vectors; i++) {
if (!vdev->msi_vectors[i].use) {
fds[i] = -1;
- continue;
+ } else if (vdev->msi_vectors[i].virq >= 0) {
+ fds[i] = event_notifier_get_fd(&vdev->msi_vectors[i].kvm_interrupt);
+ } else {
+ fds[i] = event_notifier_get_fd(&vdev->msi_vectors[i].interrupt);
}
-
- fds[i] = event_notifier_get_fd(&vdev->msi_vectors[i].interrupt);
}
ret = ioctl(vdev->fd, VFIO_DEVICE_SET_IRQS, irq_set);
@@ -676,6 +678,52 @@ static int vfio_enable_vectors(VFIODevice *vdev, bool msix)
return ret;
}
+static void vfio_add_kvm_msi_virq(VFIOMSIVector *vector, MSIMessage *msg,
+ bool msix)
+{
+ int virq;
+
+ if ((msix && !VFIO_ALLOW_KVM_MSIX) ||
+ (!msix && !VFIO_ALLOW_KVM_MSI) || !msg) {
+ return;
+ }
+
+ if (event_notifier_init(&vector->kvm_interrupt, 0)) {
+ return;
+ }
+
+ virq = kvm_irqchip_add_msi_route(kvm_state, *msg);
+ if (virq < 0) {
+ event_notifier_cleanup(&vector->kvm_interrupt);
+ return;
+ }
+
+ if (kvm_irqchip_add_irqfd_notifier(kvm_state, &vector->kvm_interrupt,
+ virq) < 0) {
+ kvm_irqchip_release_virq(kvm_state, virq);
+ event_notifier_cleanup(&vector->kvm_interrupt);
+ return;
+ }
+
+ vector->msg = *msg;
+ vector->virq = virq;
+}
+
+static void vfio_remove_kvm_msi_virq(VFIOMSIVector *vector)
+{
+ kvm_irqchip_remove_irqfd_notifier(kvm_state, &vector->kvm_interrupt,
+ vector->virq);
+ kvm_irqchip_release_virq(kvm_state, vector->virq);
+ vector->virq = -1;
+ event_notifier_cleanup(&vector->kvm_interrupt);
+}
+
+static void vfio_update_kvm_msi_virq(VFIOMSIVector *vector, MSIMessage msg)
+{
+ kvm_irqchip_update_msi_route(kvm_state, vector->virq, msg);
+ vector->msg = msg;
+}
+
static int vfio_msix_vector_do_use(PCIDevice *pdev, unsigned int nr,
MSIMessage *msg, IOHandler *handler)
{
@@ -688,30 +736,32 @@ static int vfio_msix_vector_do_use(PCIDevice *pdev, unsigned int nr,
vdev->host.function, nr);
vector = &vdev->msi_vectors[nr];
- vector->vdev = vdev;
- vector->use = true;
-
- msix_vector_use(pdev, nr);
- if (event_notifier_init(&vector->interrupt, 0)) {
- error_report("vfio: Error: event_notifier_init failed");
+ if (!vector->use) {
+ vector->vdev = vdev;
+ vector->virq = -1;
+ if (event_notifier_init(&vector->interrupt, 0)) {
+ error_report("vfio: Error: event_notifier_init failed");
+ }
+ vector->use = true;
+ msix_vector_use(pdev, nr);
}
+ qemu_set_fd_handler(event_notifier_get_fd(&vector->interrupt),
+ handler, NULL, vector);
+
/*
* Attempt to enable route through KVM irqchip,
* default to userspace handling if unavailable.
*/
- vector->virq = msg && VFIO_ALLOW_KVM_MSIX ?
- kvm_irqchip_add_msi_route(kvm_state, *msg) : -1;
- if (vector->virq < 0 ||
- kvm_irqchip_add_irqfd_notifier(kvm_state, &vector->interrupt,
- vector->virq) < 0) {
- if (vector->virq >= 0) {
- kvm_irqchip_release_virq(kvm_state, vector->virq);
- vector->virq = -1;
+ if (vector->virq >= 0) {
+ if (!msg) {
+ vfio_remove_kvm_msi_virq(vector);
+ } else {
+ vfio_update_kvm_msi_virq(vector, *msg);
}
- qemu_set_fd_handler(event_notifier_get_fd(&vector->interrupt),
- handler, NULL, vector);
+ } else {
+ vfio_add_kvm_msi_virq(vector, msg, true);
}
/*
@@ -742,7 +792,11 @@ static int vfio_msix_vector_do_use(PCIDevice *pdev, unsigned int nr,
irq_set->count = 1;
pfd = (int32_t *)&irq_set->data;
- *pfd = event_notifier_get_fd(&vector->interrupt);
+ if (vector->virq >= 0) {
+ *pfd = event_notifier_get_fd(&vector->kvm_interrupt);
+ } else {
+ *pfd = event_notifier_get_fd(&vector->interrupt);
+ }
ret = ioctl(vdev->fd, VFIO_DEVICE_SET_IRQS, irq_set);
g_free(irq_set);
@@ -764,50 +818,41 @@ static void vfio_msix_vector_release(PCIDevice *pdev, unsigned int nr)
{
VFIODevice *vdev = DO_UPCAST(VFIODevice, pdev, pdev);
VFIOMSIVector *vector = &vdev->msi_vectors[nr];
- int argsz;
- struct vfio_irq_set *irq_set;
- int32_t *pfd;
DPRINTF("%s(%04x:%02x:%02x.%x) vector %d released\n", __func__,
vdev->host.domain, vdev->host.bus, vdev->host.slot,
vdev->host.function, nr);
/*
- * XXX What's the right thing to do here? This turns off the interrupt
- * completely, but do we really just want to switch the interrupt to
- * bouncing through userspace and let msix.c drop it? Not sure.
+ * There are still old guests that mask and unmask vectors on every
+ * interrupt. If we're using QEMU bypass with a KVM irqfd, leave all of
+ * the KVM setup in place, simply switch VFIO to use the non-bypass
+ * eventfd. We'll then fire the interrupt through QEMU and the MSI-X
+ * core will mask the interrupt and set pending bits, allowing it to
+ * be re-asserted on unmask. Nothing to do if already using QEMU mode.
*/
- msix_vector_unuse(pdev, nr);
-
- argsz = sizeof(*irq_set) + sizeof(*pfd);
+ if (vector->virq >= 0) {
+ int argsz;
+ struct vfio_irq_set *irq_set;
+ int32_t *pfd;
- irq_set = g_malloc0(argsz);
- irq_set->argsz = argsz;
- irq_set->flags = VFIO_IRQ_SET_DATA_EVENTFD |
- VFIO_IRQ_SET_ACTION_TRIGGER;
- irq_set->index = VFIO_PCI_MSIX_IRQ_INDEX;
- irq_set->start = nr;
- irq_set->count = 1;
- pfd = (int32_t *)&irq_set->data;
+ argsz = sizeof(*irq_set) + sizeof(*pfd);
- *pfd = -1;
+ irq_set = g_malloc0(argsz);
+ irq_set->argsz = argsz;
+ irq_set->flags = VFIO_IRQ_SET_DATA_EVENTFD |
+ VFIO_IRQ_SET_ACTION_TRIGGER;
+ irq_set->index = VFIO_PCI_MSIX_IRQ_INDEX;
+ irq_set->start = nr;
+ irq_set->count = 1;
+ pfd = (int32_t *)&irq_set->data;
- ioctl(vdev->fd, VFIO_DEVICE_SET_IRQS, irq_set);
+ *pfd = event_notifier_get_fd(&vector->interrupt);
- g_free(irq_set);
+ ioctl(vdev->fd, VFIO_DEVICE_SET_IRQS, irq_set);
- if (vector->virq < 0) {
- qemu_set_fd_handler(event_notifier_get_fd(&vector->interrupt),
- NULL, NULL, NULL);
- } else {
- kvm_irqchip_remove_irqfd_notifier(kvm_state, &vector->interrupt,
- vector->virq);
- kvm_irqchip_release_virq(kvm_state, vector->virq);
- vector->virq = -1;
+ g_free(irq_set);
}
-
- event_notifier_cleanup(&vector->interrupt);
- vector->use = false;
}
static void vfio_enable_msix(VFIODevice *vdev)
@@ -857,28 +902,28 @@ retry:
VFIOMSIVector *vector = &vdev->msi_vectors[i];
vector->vdev = vdev;
+ vector->virq = -1;
vector->use = true;
if (event_notifier_init(&vector->interrupt, 0)) {
error_report("vfio: Error: event_notifier_init failed");
}
+ qemu_set_fd_handler(event_notifier_get_fd(&vector->interrupt),
+ vfio_msi_interrupt, NULL, vector);
+
vector->msg = msi_get_message(&vdev->pdev, i);
/*
* Attempt to enable route through KVM irqchip,
* default to userspace handling if unavailable.
*/
- vector->virq = VFIO_ALLOW_KVM_MSI ?
- kvm_irqchip_add_msi_route(kvm_state, vector->msg) : -1;
- if (vector->virq < 0 ||
- kvm_irqchip_add_irqfd_notifier(kvm_state, &vector->interrupt,
- vector->virq) < 0) {
- qemu_set_fd_handler(event_notifier_get_fd(&vector->interrupt),
- vfio_msi_interrupt, NULL, vector);
- }
+ vfio_add_kvm_msi_virq(vector, &vector->msg, false);
}
+ /* Set interrupt type prior to possible interrupts */
+ vdev->interrupt = VFIO_INT_MSI;
+
ret = vfio_enable_vectors(vdev, false);
if (ret) {
if (ret < 0) {
@@ -891,14 +936,10 @@ retry:
for (i = 0; i < vdev->nr_vectors; i++) {
VFIOMSIVector *vector = &vdev->msi_vectors[i];
if (vector->virq >= 0) {
- kvm_irqchip_remove_irqfd_notifier(kvm_state, &vector->interrupt,
- vector->virq);
- kvm_irqchip_release_virq(kvm_state, vector->virq);
- vector->virq = -1;
- } else {
- qemu_set_fd_handler(event_notifier_get_fd(&vector->interrupt),
- NULL, NULL, NULL);
+ vfio_remove_kvm_msi_virq(vector);
}
+ qemu_set_fd_handler(event_notifier_get_fd(&vector->interrupt),
+ NULL, NULL, NULL);
event_notifier_cleanup(&vector->interrupt);
}
@@ -910,11 +951,17 @@ retry:
}
vdev->nr_vectors = 0;
+ /*
+ * Failing to setup MSI doesn't really fall within any specification.
+ * Let's try leaving interrupts disabled and hope the guest figures
+ * out to fall back to INTx for this device.
+ */
+ error_report("vfio: Error: Failed to enable MSI");
+ vdev->interrupt = VFIO_INT_NONE;
+
return;
}
- vdev->interrupt = VFIO_INT_MSI;
-
DPRINTF("%s(%04x:%02x:%02x.%x) Enabled %d MSI vectors\n", __func__,
vdev->host.domain, vdev->host.bus, vdev->host.slot,
vdev->host.function, vdev->nr_vectors);
@@ -922,6 +969,20 @@ retry:
static void vfio_disable_msi_common(VFIODevice *vdev)
{
+ int i;
+
+ for (i = 0; i < vdev->nr_vectors; i++) {
+ VFIOMSIVector *vector = &vdev->msi_vectors[i];
+ if (vdev->msi_vectors[i].use) {
+ if (vector->virq >= 0) {
+ vfio_remove_kvm_msi_virq(vector);
+ }
+ qemu_set_fd_handler(event_notifier_get_fd(&vector->interrupt),
+ NULL, NULL, NULL);
+ event_notifier_cleanup(&vector->interrupt);
+ }
+ }
+
g_free(vdev->msi_vectors);
vdev->msi_vectors = NULL;
vdev->nr_vectors = 0;
@@ -943,6 +1004,7 @@ static void vfio_disable_msix(VFIODevice *vdev)
for (i = 0; i < vdev->nr_vectors; i++) {
if (vdev->msi_vectors[i].use) {
vfio_msix_vector_release(&vdev->pdev, i);
+ msix_vector_unuse(&vdev->pdev, i);
}
}
@@ -958,30 +1020,7 @@ static void vfio_disable_msix(VFIODevice *vdev)
static void vfio_disable_msi(VFIODevice *vdev)
{
- int i;
-
vfio_disable_irqindex(vdev, VFIO_PCI_MSI_IRQ_INDEX);
-
- for (i = 0; i < vdev->nr_vectors; i++) {
- VFIOMSIVector *vector = &vdev->msi_vectors[i];
-
- if (!vector->use) {
- continue;
- }
-
- if (vector->virq >= 0) {
- kvm_irqchip_remove_irqfd_notifier(kvm_state,
- &vector->interrupt, vector->virq);
- kvm_irqchip_release_virq(kvm_state, vector->virq);
- vector->virq = -1;
- } else {
- qemu_set_fd_handler(event_notifier_get_fd(&vector->interrupt),
- NULL, NULL, NULL);
- }
-
- event_notifier_cleanup(&vector->interrupt);
- }
-
vfio_disable_msi_common(vdev);
DPRINTF("%s(%04x:%02x:%02x.%x)\n", __func__, vdev->host.domain,
@@ -1001,17 +1040,7 @@ static void vfio_update_msi(VFIODevice *vdev)
}
msg = msi_get_message(&vdev->pdev, i);
-
- if (msg.address != vector->msg.address ||
- msg.data != vector->msg.data) {
-
- DPRINTF("%s(%04x:%02x:%02x.%x) MSI vector %d changed\n",
- __func__, vdev->host.domain, vdev->host.bus,
- vdev->host.slot, vdev->host.function, i);
-
- kvm_irqchip_update_msi_route(kvm_state, vector->virq, msg);
- vector->msg = msg;
- }
+ vfio_update_kvm_msi_virq(vector, msg);
}
}
--
1.8.3.1