From f1d0f15a6d46bd47e7658e44a004c8898c8cb91e Mon Sep 17 00:00:00 2001 From: "Michael S. Tsirkin" Date: Mon, 24 Dec 2012 17:35:27 +0200 Subject: [PATCH] virtio: backend virtqueue notifier masking some backends (notably vhost) can mask events at their source in a way that is more efficient than masking through kvm. Specifically - masking in kvm uses rcu write side so it has high latency - in kvm on unmask we always send an interrupt masking at source does not have these issues. Add such support in virtio.h and use in virtio-pci. Signed-off-by: Michael S. Tsirkin --- hw/virtio-pci.c | 79 ++++++++++++++++++++++++++++++++++++++++++++++++++------- hw/virtio.h | 13 ++++++++++ 2 files changed, 83 insertions(+), 9 deletions(-) diff --git a/hw/virtio-pci.c b/hw/virtio-pci.c index 6b6f25bd06..1f35922f65 100644 --- a/hw/virtio-pci.c +++ b/hw/virtio-pci.c @@ -510,6 +510,31 @@ static void kvm_virtio_pci_vq_vector_release(VirtIOPCIProxy *proxy, } } +static int kvm_virtio_pci_irqfd_use(VirtIOPCIProxy *proxy, + unsigned int queue_no, + unsigned int vector) +{ + VirtIOIRQFD *irqfd = &proxy->vector_irqfd[vector]; + VirtQueue *vq = virtio_get_queue(proxy->vdev, queue_no); + EventNotifier *n = virtio_queue_get_guest_notifier(vq); + int ret; + ret = kvm_irqchip_add_irqfd_notifier(kvm_state, n, irqfd->virq); + return ret; +} + +static void kvm_virtio_pci_irqfd_release(VirtIOPCIProxy *proxy, + unsigned int queue_no, + unsigned int vector) +{ + VirtQueue *vq = virtio_get_queue(proxy->vdev, queue_no); + EventNotifier *n = virtio_queue_get_guest_notifier(vq); + VirtIOIRQFD *irqfd = &proxy->vector_irqfd[vector]; + int ret; + + ret = kvm_irqchip_remove_irqfd_notifier(kvm_state, n, irqfd->virq); + assert(ret == 0); +} + static int kvm_virtio_pci_vector_use(VirtIOPCIProxy *proxy, int nvqs) { PCIDevice *dev = &proxy->pci_dev; @@ -531,6 +556,16 @@ static int kvm_virtio_pci_vector_use(VirtIOPCIProxy *proxy, int nvqs) if (ret < 0) { goto undo; } + /* If guest supports masking, set up irqfd now. + * Otherwise, delay until unmasked in the frontend. + */ + if (proxy->vdev->guest_notifier_mask) { + ret = kvm_virtio_pci_irqfd_use(proxy, queue_no, vector); + if (ret < 0) { + kvm_virtio_pci_vq_vector_release(proxy, vector); + goto undo; + } + } } return 0; @@ -540,6 +575,9 @@ undo: if (vector >= msix_nr_vectors_allocated(dev)) { continue; } + if (proxy->vdev->guest_notifier_mask) { + kvm_virtio_pci_irqfd_release(proxy, vector, queue_no); + } kvm_virtio_pci_vq_vector_release(proxy, vector); } return ret; @@ -560,6 +598,12 @@ static void kvm_virtio_pci_vector_release(VirtIOPCIProxy *proxy, int nvqs) if (vector >= msix_nr_vectors_allocated(dev)) { continue; } + /* If guest supports masking, clean up irqfd now. + * Otherwise, it was cleaned when masked in the frontend. + */ + if (proxy->vdev->guest_notifier_mask) { + kvm_virtio_pci_irqfd_release(proxy, vector, queue_no); + } kvm_virtio_pci_vq_vector_release(proxy, vector); } } @@ -581,7 +625,19 @@ static int kvm_virtio_pci_vq_vector_unmask(VirtIOPCIProxy *proxy, } } - ret = kvm_irqchip_add_irqfd_notifier(kvm_state, n, irqfd->virq); + /* If guest supports masking, irqfd is already setup, unmask it. + * Otherwise, set it up now. + */ + if (proxy->vdev->guest_notifier_mask) { + proxy->vdev->guest_notifier_mask(proxy->vdev, queue_no, false); + /* Test after unmasking to avoid losing events. */ + if (proxy->vdev->guest_notifier_pending && + proxy->vdev->guest_notifier_pending(proxy->vdev, queue_no)) { + event_notifier_set(n); + } + } else { + ret = kvm_virtio_pci_irqfd_use(proxy, queue_no, vector); + } return ret; } @@ -589,13 +645,14 @@ static void kvm_virtio_pci_vq_vector_mask(VirtIOPCIProxy *proxy, unsigned int queue_no, unsigned int vector) { - VirtQueue *vq = virtio_get_queue(proxy->vdev, queue_no); - EventNotifier *n = virtio_queue_get_guest_notifier(vq); - VirtIOIRQFD *irqfd = &proxy->vector_irqfd[vector]; - int ret; - - ret = kvm_irqchip_remove_irqfd_notifier(kvm_state, n, irqfd->virq); - assert(ret == 0); + /* If guest supports masking, keep irqfd but mask it. + * Otherwise, clean it up now. + */ + if (proxy->vdev->guest_notifier_mask) { + proxy->vdev->guest_notifier_mask(proxy->vdev, queue_no, true); + } else { + kvm_virtio_pci_irqfd_release(proxy, vector, queue_no); + } } static int kvm_virtio_pci_vector_unmask(PCIDevice *dev, unsigned vector, @@ -668,7 +725,11 @@ static void kvm_virtio_pci_vector_poll(PCIDevice *dev, } vq = virtio_get_queue(vdev, queue_no); notifier = virtio_queue_get_guest_notifier(vq); - if (event_notifier_test_and_clear(notifier)) { + if (vdev->guest_notifier_pending) { + if (vdev->guest_notifier_pending(vdev, queue_no)) { + msix_set_pending(dev, vector); + } + } else if (event_notifier_test_and_clear(notifier)) { msix_set_pending(dev, vector); } } diff --git a/hw/virtio.h b/hw/virtio.h index 329b426fc0..b9f1873fd6 100644 --- a/hw/virtio.h +++ b/hw/virtio.h @@ -126,6 +126,19 @@ struct VirtIODevice void (*set_config)(VirtIODevice *vdev, const uint8_t *config); void (*reset)(VirtIODevice *vdev); void (*set_status)(VirtIODevice *vdev, uint8_t val); + /* Test and clear event pending status. + * Should be called after unmask to avoid losing events. + * If backend does not support masking, + * must check in frontend instead. + */ + bool (*guest_notifier_pending)(VirtIODevice *vdev, int n); + /* Mask/unmask events from this vq. Any events reported + * while masked will become pending. + * If backend does not support masking, + * must mask in frontend instead. + */ + void (*guest_notifier_mask)(VirtIODevice *vdev, int n, bool mask); + VirtQueue *vq; const VirtIOBindings *binding; DeviceState *binding_opaque; -- 2.11.4.GIT