Commit fb5f8164 authored by Eric Auger's avatar Eric Auger Committed by Alex Williamson
Browse files

hw/vfio/platform: add irqfd support 



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: default avatarAlvise Rigo <a.rigo@virtualopensystems.com>
Signed-off-by: default avatarEric Auger <eric.auger@linaro.org>
Reviewed-by: default avatarAlex Bennée <alex.bennee@linaro.org>
Tested-by: default avatarVikram Sethi <vikrams@codeaurora.org>
Acked-by: default avatarPeter Maydell <peter.maydell@linaro.org>
Signed-off-by: default avatarAlex Williamson <alex.williamson@redhat.com>
parent 879904e8

hw/vfio/platform.c

+100 −0
Original line number Diff line number Diff line
@@ -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: resamplefd event_notifier_init failed");

        return NULL;

    }



    QLIST_INSERT_HEAD(&vdev->intp_list, intp, next);

    return intp;
@@ -315,6 +324,94 @@ static int vfio_start_eventfd_injection(VFIOINTp *intp) 
    return ret;

}



/*

 * Functions used for irqfd

 */



/**

 * 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;



    if (!kvm_irqfds_enabled() || !kvm_resamplefds_enabled() ||

        !vdev->irqfd_allowed) {

        return;

    }



    QLIST_FOREACH(intp, &vdev->intp_list, next) {

        if (intp->qemuirq == irq) {

            break;

        }

    }

    assert(intp);



    /* 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's resume injection with irqfd setup */

    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;

}



/* VFIO skeleton */



static void vfio_platform_compute_needs_reset(VFIODevice *vbasedev)
@@ -584,17 +681,20 @@ 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(),

};



static void vfio_platform_class_init(ObjectClass *klass, void *data)

{

    DeviceClass *dc = DEVICE_CLASS(klass);

    SysBusDeviceClass *sbc = SYS_BUS_DEVICE_CLASS(klass);



    dc->realize = vfio_platform_realize;

    dc->props = vfio_platform_dev_properties;

    dc->vmsd = &vfio_platform_vmstate;

    dc->desc = "VFIO-based platform device assignment";

    sbc->connect_irq_notifier = vfio_start_irqfd_injection;

    set_bit(DEVICE_CATEGORY_MISC, dc->categories);

}

include/hw/vfio/vfio-platform.h

+2 −0
Original line number Diff line number Diff line
@@ -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 {

trace-events

+1 −0
Original line number Diff line number Diff line
@@ -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