On Mon, 2015-06-15 at 17:33 +0100, Eric Auger wrote:
> This patch aims at optimizing IRQ handling using irqfd framework.
>
> Instead of handling the eventfds on user-side they are handled on
> kernel side using
> - the KVM irqfd framework,
> - the VFIO driver virqfd framework.
>
> the virtual IRQ completion is trapped at interrupt controller
> This removes the need for fast/slow path swap.
>
> Overall this brings significant performance improvements.
>
> Signed-off-by: Alvise Rigo <a.r...@virtualopensystems.com>
> Signed-off-by: Eric Auger <eric.au...@linaro.org>
> Reviewed-by: Alex Bennée <alex.ben...@linaro.org>
> Tested-by: Vikram Sethi <vikr...@codeaurora.org>
>
> ---
> v15 -> v16:
> - add Vikram's T-b
>
> v13 -> v14:
> - use connect_irq_notifier
> - remove trace_vfio_platform_start_eventfd
>
> v12 -> v13:
> - setup the new mechanism for starting irqfd, based on
> LinkPropertySetter override
> - use kvm_irqchip_[add,remove]_irqfd_notifier new functions: no need
> to bother about gsi (hence virtualID could be removed with small
> change in trace-events)
>
> v10 -> v11:
> - Add Alex' Reviewed-by
> - introduce kvm_accel in this patch and initialize it
>
> v5 -> v6
> - rely on kvm_irqfds_enabled() and kvm_resamplefds_enabled()
> - guard KVM code with #ifdef CONFIG_KVM
>
> v3 -> v4:
> [Alvise Rigo]
> Use of VFIO Platform driver v6 unmask/virqfd feature and removal
> of resamplefd handler. Physical IRQ unmasking is now done in
> VFIO driver.
>
> v3:
> [Eric Auger]
> initial support with resamplefd handled on QEMU side since the
> unmask was not supported on VFIO platform driver v5.
> ---
> hw/vfio/platform.c | 107
> ++++++++++++++++++++++++++++++++++++++++
> include/hw/vfio/vfio-platform.h | 2 +
> trace-events | 1 +
> 3 files changed, 110 insertions(+)
>
> diff --git a/hw/vfio/platform.c b/hw/vfio/platform.c
> index 9382bb7..1d44085 100644
> --- a/hw/vfio/platform.c
> +++ b/hw/vfio/platform.c
> @@ -26,6 +26,7 @@
> #include "hw/sysbus.h"
> #include "trace.h"
> #include "hw/platform-bus.h"
> +#include "sysemu/kvm.h"
>
> /*
> * Functions used whatever the injection method
> @@ -51,6 +52,7 @@ static VFIOINTp *vfio_init_intp(VFIODevice *vbasedev,
> intp->pin = info.index;
> intp->flags = info.flags;
> intp->state = VFIO_IRQ_INACTIVE;
> + intp->kvm_accel = false;
>
> sysbus_init_irq(sbdev, &intp->qemuirq);
>
> @@ -61,6 +63,13 @@ static VFIOINTp *vfio_init_intp(VFIODevice *vbasedev,
> error_report("vfio: Error: trigger event_notifier_init failed ");
> return NULL;
> }
> + /* Get an eventfd for resample/unmask */
> + ret = event_notifier_init(&intp->unmask, 0);
> + if (ret) {
> + g_free(intp);
> + error_report("vfio: Error: resample event_notifier_init failed eoi");
> + return NULL;
> + }
>
> QLIST_INSERT_HEAD(&vdev->intp_list, intp, next);
> return intp;
> @@ -315,6 +324,95 @@ static int vfio_start_eventfd_injection(VFIOINTp *intp)
> return ret;
> }
>
> +/*
> + * Functions used for irqfd
> + */
> +
> +#ifdef CONFIG_KVM
> +
> +/**
> + * vfio_set_resample_eventfd - sets the resamplefd for an IRQ
> + * @intp: the IRQ struct handle
> + * programs the VFIO driver to unmask this IRQ when the
> + * intp->unmask eventfd is triggered
> + */
> +static int vfio_set_resample_eventfd(VFIOINTp *intp)
> +{
> + VFIODevice *vbasedev = &intp->vdev->vbasedev;
> + struct vfio_irq_set *irq_set;
> + int argsz, ret;
> + int32_t *pfd;
> +
> + argsz = sizeof(*irq_set) + sizeof(*pfd);
> + irq_set = g_malloc0(argsz);
> + irq_set->argsz = argsz;
> + irq_set->flags = VFIO_IRQ_SET_DATA_EVENTFD | VFIO_IRQ_SET_ACTION_UNMASK;
> + irq_set->index = intp->pin;
> + irq_set->start = 0;
> + irq_set->count = 1;
> + pfd = (int32_t *)&irq_set->data;
> + *pfd = event_notifier_get_fd(&intp->unmask);
> + qemu_set_fd_handler(*pfd, NULL, NULL, NULL);
> + ret = ioctl(vbasedev->fd, VFIO_DEVICE_SET_IRQS, irq_set);
> + g_free(irq_set);
> + if (ret < 0) {
> + error_report("vfio: Failed to set resample eventfd: %m");
> + }
> + return ret;
> +}
> +
> +static void vfio_start_irqfd_injection(SysBusDevice *sbdev, qemu_irq irq)
> +{
> + VFIOPlatformDevice *vdev = VFIO_PLATFORM_DEVICE(sbdev);
> + VFIOINTp *intp;
> + bool found = false;
> +
> + QLIST_FOREACH(intp, &vdev->intp_list, next) {
> + if (intp->qemuirq == irq) {
> + found = true;
> + break;
> + }
> + }
> + assert(found);
You can simply assert(intp) and get rid of found.
> +
> + /* Get to a known interrupt state */
> + qemu_set_fd_handler(event_notifier_get_fd(&intp->interrupt),
> + NULL, NULL, vdev);
> +
> + vfio_mask_single_irqindex(&vdev->vbasedev, intp->pin);
> + qemu_set_irq(intp->qemuirq, 0);
> +
> + if (kvm_irqchip_add_irqfd_notifier(kvm_state, &intp->interrupt,
> + &intp->unmask, irq) < 0) {
> + goto fail_irqfd;
> + }
> +
> + if (vfio_set_trigger_eventfd(intp, NULL) < 0) {
> + goto fail_vfio;
> + }
> + if (vfio_set_resample_eventfd(intp) < 0) {
> + goto fail_vfio;
> + }
> +
> + /* Let'em rip */
> + vfio_unmask_single_irqindex(&vdev->vbasedev, intp->pin);
> +
> + intp->kvm_accel = true;
> +
> + trace_vfio_platform_start_irqfd_injection(intp->pin,
> + event_notifier_get_fd(&intp->interrupt),
> + event_notifier_get_fd(&intp->unmask));
> + return;
> +fail_vfio:
> + kvm_irqchip_remove_irqfd_notifier(kvm_state, &intp->interrupt, irq);
> +fail_irqfd:
> + vfio_start_eventfd_injection(intp);
> + vfio_unmask_single_irqindex(&vdev->vbasedev, intp->pin);
> + return;
> +}
> +
> +#endif /* CONFIG_KVM */
> +
> /* VFIO skeleton */
>
> static void vfio_platform_compute_needs_reset(VFIODevice *vbasedev)
> @@ -548,6 +646,7 @@ static void vfio_platform_realize(DeviceState *dev, Error
> **errp)
> {
> VFIOPlatformDevice *vdev = VFIO_PLATFORM_DEVICE(dev);
> SysBusDevice *sbdev = SYS_BUS_DEVICE(dev);
> + SysBusDeviceClass *sbc = SYS_BUS_DEVICE_GET_CLASS(dev);
> VFIODevice *vbasedev = &vdev->vbasedev;
> VFIOINTp *intp;
> int i, ret;
> @@ -555,6 +654,13 @@ static void vfio_platform_realize(DeviceState *dev,
> Error **errp)
> vbasedev->type = VFIO_DEVICE_TYPE_PLATFORM;
> vbasedev->ops = &vfio_platform_ops;
>
> +#ifdef CONFIG_KVM
> + if (kvm_irqfds_enabled() && kvm_resamplefds_enabled() &&
> + vdev->irqfd_allowed) {
> + sbc->connect_irq_notifier = vfio_start_irqfd_injection;
Should we be abstracting this to a
sysbus_register_connect_irq_notifier()? It seems a littler personal to
be reaching in and setting it ourselves and would avoid us needing to
reference the class.
> + }
> +#endif
> +
> trace_vfio_platform_realize(vbasedev->name, vdev->compat);
>
> ret = vfio_base_device_init(vbasedev);
> @@ -584,6 +690,7 @@ static Property vfio_platform_dev_properties[] = {
> DEFINE_PROP_BOOL("x-mmap", VFIOPlatformDevice, vbasedev.allow_mmap,
> true),
> DEFINE_PROP_UINT32("mmap-timeout-ms", VFIOPlatformDevice,
> mmap_timeout, 1100),
> + DEFINE_PROP_BOOL("x-irqfd", VFIOPlatformDevice, irqfd_allowed, true),
> DEFINE_PROP_END_OF_LIST(),
> };
>
> diff --git a/include/hw/vfio/vfio-platform.h b/include/hw/vfio/vfio-platform.h
> index 26b2ad6..c5cf1d7 100644
> --- a/include/hw/vfio/vfio-platform.h
> +++ b/include/hw/vfio/vfio-platform.h
> @@ -41,6 +41,7 @@ typedef struct VFIOINTp {
> int state; /* inactive, pending, active */
> uint8_t pin; /* index */
> uint32_t flags; /* IRQ info flags */
> + bool kvm_accel; /* set when QEMU bypass through KVM enabled */
> } VFIOINTp;
>
> /* function type for user side eventfd handler */
> @@ -57,6 +58,7 @@ typedef struct VFIOPlatformDevice {
> uint32_t mmap_timeout; /* delay to re-enable mmaps after interrupt */
> QEMUTimer *mmap_timer; /* allows fast-path resume after IRQ hit */
> QemuMutex intp_mutex; /* protect the intp_list IRQ state */
> + bool irqfd_allowed; /* debug option to force irqfd on/off */
> } VFIOPlatformDevice;
>
> typedef struct VFIOPlatformDeviceClass {
> diff --git a/trace-events b/trace-events
> index 6060d36..4390381 100644
> --- a/trace-events
> +++ b/trace-events
> @@ -1594,6 +1594,7 @@ vfio_platform_intp_interrupt(int pin, int fd) "Inject
> IRQ #%d (fd = %d)"
> vfio_platform_intp_inject_pending_lockheld(int pin, int fd) "Inject pending
> IRQ #%d (fd = %d)"
> vfio_platform_populate_interrupts(int pin, int count, int flags) "- IRQ
> index %d: count %d, flags=0x%x"
> vfio_intp_interrupt_set_pending(int index) "irq %d is set PENDING"
> +vfio_platform_start_irqfd_injection(int index, int fd, int resamplefd) "IRQ
> index=%d, fd = %d, resamplefd = %d"
>
> #hw/acpi/memory_hotplug.c
> mhp_acpi_invalid_slot_selected(uint32_t slot) "0x%"PRIx32
