From 81ee28858d0082b300184c9fcfc10480c67aa74d Mon Sep 17 00:00:00 2001 From: Alex Williamson 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 RH-Acked-by: Amos Kong RH-Acked-by: Laszlo Ersek 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 Signed-off-by: Miroslav Rezanina --- 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