diff options
| -rw-r--r-- | hw/vfio_pci.c | 65 | ||||
| -rw-r--r-- | hw/vfio_pci_int.h | 4 |
2 files changed, 44 insertions, 25 deletions
diff --git a/hw/vfio_pci.c b/hw/vfio_pci.c index a1eeced8fd..7ec9c30cd8 100644 --- a/hw/vfio_pci.c +++ b/hw/vfio_pci.c @@ -92,6 +92,34 @@ static void vfio_unmask_intx(VFIODevice *vdev) ioctl(vdev->fd, VFIO_DEVICE_SET_IRQS, &irq_set); } +/* + * Disabling BAR mmaping can be slow, but toggling it around INTx can + * also be a huge overhead. We try to get the best of both worlds by + * waiting until an interrupt to disable mmaps (subsequent transitions + * to the same state are effectively no overhead). If the interrupt has + * been serviced and the time gap is long enough, we re-enable mmaps for + * performance. This works well for things like graphics cards, which + * may not use their interrupt at all and are penalized to an unusable + * level by read/write BAR traps. Other devices, like NICs, have more + * regular interrupts and see much better latency by staying in non-mmap + * mode. We therefore set the default mmap_timeout such that a ping + * is just enough to keep the mmap disabled. Users can experiment with + * other options with the x-intx-mmap-timeout-ms parameter (a value of + * zero disables the timer). + */ +static void vfio_intx_mmap_enable(void *opaque) +{ + VFIODevice *vdev = opaque; + + if (vdev->intx.pending) { + qemu_mod_timer(vdev->intx.mmap_timer, + qemu_get_clock_ms(vm_clock) + vdev->intx.mmap_timeout); + return; + } + + vfio_mmap_set_enabled(vdev, true); +} + static void vfio_intx_interrupt(void *opaque) { VFIODevice *vdev = opaque; @@ -106,6 +134,11 @@ static void vfio_intx_interrupt(void *opaque) vdev->intx.pending = true; qemu_set_irq(vdev->pdev.irq[vdev->intx.pin], 1); + vfio_mmap_set_enabled(vdev, false); + if (vdev->intx.mmap_timeout) { + qemu_mod_timer(vdev->intx.mmap_timer, + qemu_get_clock_ms(vm_clock) + vdev->intx.mmap_timeout); + } } static void vfio_eoi(VFIODevice *vdev) @@ -141,7 +174,7 @@ static int vfio_enable_intx(VFIODevice *vdev) uint8_t pin = vfio_pci_read_config(&vdev->pdev, PCI_INTERRUPT_PIN, 1); int ret; - if (vdev->intx.disabled || !pin) { + if (!pin) { return 0; } @@ -162,16 +195,6 @@ static int vfio_enable_intx(VFIODevice *vdev) return -errno; } - /* - * Disable mmaps so we can trap on BAR accesses. We interpret any - * access as a response to an interrupt and unmask the physical - * device. The device will re-assert if the interrupt is still - * pending. We'll likely retrigger on the host multiple times per - * guest interrupt, but without EOI notification it's better than - * nothing. Acceleration paths through KVM will avoid this. - */ - vfio_mmap_set_enabled(vdev, false); - vdev->interrupt = VFIO_INT_INTx; DPRINTF("%s(%04x:%02x:%02x.%x)\n", __func__, vdev->host.domain, @@ -184,6 +207,7 @@ static void vfio_disable_intx(VFIODevice *vdev) { int fd; + qemu_del_timer(vdev->intx.mmap_timer); vfio_disable_irqindex(vdev, VFIO_PCI_INTX_IRQ_INDEX); vdev->intx.pending = false; qemu_set_irq(vdev->pdev.irq[vdev->intx.pin], 0); @@ -1766,17 +1790,8 @@ static int vfio_initfn(PCIDevice *pdev) } if (vfio_pci_read_config(&vdev->pdev, PCI_INTERRUPT_PIN, 1)) { - if (vdev->intx.intx && strcmp(vdev->intx.intx, "off")) { - error_report("vfio: Unknown option x-intx=%s, " - "valid options: \"off\".\n", vdev->intx.intx); - ret = -EINVAL; - goto out_teardown; - } - - if (vdev->intx.intx && !strcmp(vdev->intx.intx, "off")) { - vdev->intx.disabled = true; - } - + vdev->intx.mmap_timer = qemu_new_timer_ms(vm_clock, + vfio_intx_mmap_enable, vdev); ret = vfio_enable_intx(vdev); if (ret) { goto out_teardown; @@ -1802,6 +1817,9 @@ static void vfio_exitfn(PCIDevice *pdev) pci_device_set_intx_routing_notifier(&vdev->pdev, NULL); vfio_disable_interrupts(vdev); + if (vdev->intx.mmap_timer) { + qemu_free_timer(vdev->intx.mmap_timer); + } vfio_teardown_msi(vdev); vfio_unmap_bars(vdev); vfio_put_device(vdev); @@ -1826,7 +1844,8 @@ static void vfio_pci_reset(DeviceState *dev) static Property vfio_pci_dev_properties[] = { DEFINE_PROP_PCI_HOST_DEVADDR("host", VFIODevice, host), - DEFINE_PROP_STRING("x-intx", VFIODevice, intx.intx), + DEFINE_PROP_UINT32("x-intx-mmap-timeout-ms", VFIODevice, + intx.mmap_timeout, 1100), /* * TODO - support passed fds... is this necessary? * DEFINE_PROP_STRING("vfiofd", VFIODevice, vfiofd_name), diff --git a/hw/vfio_pci_int.h b/hw/vfio_pci_int.h index 3812d8d7f1..e69bf5f939 100644 --- a/hw/vfio_pci_int.h +++ b/hw/vfio_pci_int.h @@ -36,8 +36,8 @@ typedef struct VFIOINTx { EventNotifier interrupt; /* eventfd triggered on interrupt */ EventNotifier unmask; /* eventfd for unmask on QEMU bypass */ PCIINTxRoute route; /* routing info for QEMU bypass */ - bool disabled; - char *intx; + uint32_t mmap_timeout; /* delay to re-enable mmaps after interrupt */ + QEMUTimer *mmap_timer; /* enable mmaps after periods w/o interrupts */ } VFIOINTx; struct VFIODevice; |