Record data writes that come through the NVIDIA BAR0 quirk, if we get enough in a row that we're only passing through, automatically enable an ioeventfd for it. The primary target for this is the MSI-ACK that NVIDIA uses to allow the MSI interrupt to re-trigger, which is a 4-byte write, data value 0x0 to offset 0x704 into the quirk, 0x88704 into BAR0 MMIO space. For an interrupt latency sensitive micro- benchmark, this takes us from 83% of performance versus disabling the quirk entirely (which GeForce cannot do), to to almost 90%. Signed-off-by: Alex Williamson --- hw/vfio/pci-quirks.c | 89 +++++++++++++++++++++++++++++++++++++++++++++++++- hw/vfio/pci.h | 2 + 2 files changed, 89 insertions(+), 2 deletions(-) diff --git a/hw/vfio/pci-quirks.c b/hw/vfio/pci-quirks.c index e4cf4ea2dd9c..e739efe601b1 100644 --- a/hw/vfio/pci-quirks.c +++ b/hw/vfio/pci-quirks.c @@ -203,6 +203,7 @@ typedef struct VFIOConfigMirrorQuirk { uint32_t offset; uint8_t bar; MemoryRegion *mem; + uint8_t data[]; } VFIOConfigMirrorQuirk; static uint64_t vfio_generic_quirk_mirror_read(void *opaque, @@ -297,6 +298,50 @@ static void vfio_ioeventfd_exit(VFIOIOEventFD *ioeventfd) g_free(ioeventfd); } +static void vfio_ioeventfd_handler(void *opaque) +{ + VFIOIOEventFD *ioeventfd = opaque; + + if (event_notifier_test_and_clear(&ioeventfd->e)) { + vfio_region_write(ioeventfd->region, ioeventfd->region_addr, + ioeventfd->data, ioeventfd->size); + } +} + +static VFIOIOEventFD *vfio_ioeventfd_init(VFIOPCIDevice *vdev, + MemoryRegion *mr, hwaddr addr, + unsigned size, uint64_t data, + VFIORegion *region, + hwaddr region_addr) +{ + VFIOIOEventFD *ioeventfd = g_malloc0(sizeof(*ioeventfd)); + + if (event_notifier_init(&ioeventfd->e, 0)) { + g_free(ioeventfd); + return NULL; + } + + ioeventfd->mr = mr; + ioeventfd->addr = addr; + ioeventfd->size = size; + ioeventfd->match_data = true; + ioeventfd->data = data; + ioeventfd->region = region; + ioeventfd->region_addr = region_addr; + + qemu_set_fd_handler(event_notifier_get_fd(&ioeventfd->e), + vfio_ioeventfd_handler, NULL, ioeventfd); + memory_region_add_eventfd(ioeventfd->mr, ioeventfd->addr, + ioeventfd->size, ioeventfd->match_data, + ioeventfd->data, &ioeventfd->e); + + info_report("Enabled automatic ioeventfd acceleration for %s region %d, " + "offset 0x%"HWADDR_PRIx", data 0x%"PRIx64", size %u", + vdev->vbasedev.name, region->nr, region_addr, data, size); + + return ioeventfd; +} + static void vfio_vga_probe_ati_3c3_quirk(VFIOPCIDevice *vdev) { VFIOQuirk *quirk; @@ -732,6 +777,13 @@ static void vfio_probe_nvidia_bar5_quirk(VFIOPCIDevice *vdev, int nr) trace_vfio_quirk_nvidia_bar5_probe(vdev->vbasedev.name); } +typedef struct LastDataSet { + hwaddr addr; + uint64_t data; + unsigned size; + int count; +} LastDataSet; + /* * Finally, BAR0 itself. We want to redirect any accesses to either * 0x1800 or 0x88000 through the PCI config space access functions. @@ -742,6 +794,7 @@ static void vfio_nvidia_quirk_mirror_write(void *opaque, hwaddr addr, VFIOConfigMirrorQuirk *mirror = opaque; VFIOPCIDevice *vdev = mirror->vdev; PCIDevice *pdev = &vdev->pdev; + LastDataSet *last = (LastDataSet *)&mirror->data; vfio_generic_quirk_mirror_write(opaque, addr, data, size); @@ -756,6 +809,38 @@ static void vfio_nvidia_quirk_mirror_write(void *opaque, hwaddr addr, addr + mirror->offset, data, size); trace_vfio_quirk_nvidia_bar0_msi_ack(vdev->vbasedev.name); } + + /* + * Automatically add an ioeventfd to handle any repeated write with the + * same data and size above the standard PCI config space header. This is + * primarily expected to accelerate the MSI-ACK behavior, such as noted + * above. Current hardware/drivers should trigger an ioeventfd at config + * offset 0x704 (region offset 0x88704), with data 0x0, size 4. + */ + if (addr > PCI_STD_HEADER_SIZEOF) { + if (addr != last->addr || data != last->data || size != last->size) { + last->addr = addr; + last->data = data; + last->size = size; + last->count = 1; + } else if (++last->count > 10) { + VFIOIOEventFD *ioeventfd; + + ioeventfd = vfio_ioeventfd_init(vdev, mirror->mem, addr, size, data, + &vdev->bars[mirror->bar].region, + mirror->offset + addr); + if (ioeventfd) { + VFIOQuirk *quirk; + + QLIST_FOREACH(quirk, &vdev->bars[mirror->bar].quirks, next) { + if (quirk->data == mirror) { + QLIST_INSERT_HEAD(&quirk->ioeventfds, ioeventfd, next); + break; + } + } + } + } + } } static const MemoryRegionOps vfio_nvidia_mirror_quirk = { @@ -776,7 +861,7 @@ static void vfio_probe_nvidia_bar0_quirk(VFIOPCIDevice *vdev, int nr) } quirk = vfio_quirk_alloc(1); - mirror = quirk->data = g_malloc0(sizeof(*mirror)); + mirror = quirk->data = g_malloc0(sizeof(*mirror) + sizeof(LastDataSet)); mirror->mem = quirk->mem; mirror->vdev = vdev; mirror->offset = 0x88000; @@ -794,7 +879,7 @@ static void vfio_probe_nvidia_bar0_quirk(VFIOPCIDevice *vdev, int nr) /* The 0x1800 offset mirror only seems to get used by legacy VGA */ if (vdev->vga) { quirk = vfio_quirk_alloc(1); - mirror = quirk->data = g_malloc0(sizeof(*mirror)); + mirror = quirk->data = g_malloc0(sizeof(*mirror) + sizeof(LastDataSet)); mirror->mem = quirk->mem; mirror->vdev = vdev; mirror->offset = 0x1800; diff --git a/hw/vfio/pci.h b/hw/vfio/pci.h index 146065c2f715..ec53b9935725 100644 --- a/hw/vfio/pci.h +++ b/hw/vfio/pci.h @@ -32,6 +32,8 @@ typedef struct VFIOIOEventFD { bool match_data; uint64_t data; EventNotifier e; + VFIORegion *region; + hwaddr region_addr; } VFIOIOEventFD; typedef struct VFIOQuirk {