vfio_pci_intrs.c

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/*
 * VFIO PCI interrupt handling
 *
 * Copyright (C) 2012 Red Hat, Inc.  All rights reserved.
 *     Author: Alex Williamson <[email protected]>
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 *
 * Derived from original vfio:
 * Copyright 2010 Cisco Systems, Inc.  All rights reserved.
 * Author: Tom Lyon, [email protected]
 */

#include <linux/device.h>
#include <linux/interrupt.h>
#include <linux/eventfd.h>
#include <linux/pci.h>
#include <linux/file.h>
#include <linux/poll.h>
#include <linux/vfio.h>
#include <linux/wait.h>
#include <linux/workqueue.h>

#include "vfio_pci_private.h"

/*
 * IRQfd - generic
 */
struct virqfd {
    struct vfio_pci_device  *vdev;
    struct eventfd_ctx  *eventfd;
    int         (*handler)(struct vfio_pci_device *, void *);
    void            (*thread)(struct vfio_pci_device *, void *);
    void            *data;
    struct work_struct  inject;
    wait_queue_t        wait;
    poll_table      pt;
    struct work_struct  shutdown;
    struct virqfd       **pvirqfd;
};

static struct workqueue_struct *vfio_irqfd_cleanup_wq;

int __init vfio_pci_virqfd_init(void)
{
    vfio_irqfd_cleanup_wq =
        create_singlethread_workqueue("vfio-irqfd-cleanup");
    if (!vfio_irqfd_cleanup_wq)
        return -ENOMEM;

    return 0;
}

void vfio_pci_virqfd_exit(void)
{
    destroy_workqueue(vfio_irqfd_cleanup_wq);
}

static void virqfd_deactivate(struct virqfd *virqfd)
{
    queue_work(vfio_irqfd_cleanup_wq, &virqfd->shutdown);
}

static int virqfd_wakeup(wait_queue_t *wait, unsigned mode, int sync, void *key)
{
    struct virqfd *virqfd = container_of(wait, struct virqfd, wait);
    unsigned long flags = (unsigned long)key;

    if (flags & POLLIN) {
        /* An event has been signaled, call function */
        if ((!virqfd->handler ||
             virqfd->handler(virqfd->vdev, virqfd->data)) &&
            virqfd->thread)
            schedule_work(&virqfd->inject);
    }

    if (flags & POLLHUP) {
        unsigned long flags;
        spin_lock_irqsave(&virqfd->vdev->irqlock, flags);

        /*
         * The eventfd is closing, if the virqfd has not yet been
         * queued for release, as determined by testing whether the
         * vdev pointer to it is still valid, queue it now.  As
         * with kvm irqfds, we know we won't race against the virqfd
         * going away because we hold wqh->lock to get here.
         */
        if (*(virqfd->pvirqfd) == virqfd) {
            *(virqfd->pvirqfd) = NULL;
            virqfd_deactivate(virqfd);
        }

        spin_unlock_irqrestore(&virqfd->vdev->irqlock, flags);
    }

    return 0;
}

static void virqfd_ptable_queue_proc(struct file *file,
                     wait_queue_head_t *wqh, poll_table *pt)
{
    struct virqfd *virqfd = container_of(pt, struct virqfd, pt);
    add_wait_queue(wqh, &virqfd->wait);
}

static void virqfd_shutdown(struct work_struct *work)
{
    struct virqfd *virqfd = container_of(work, struct virqfd, shutdown);
    u64 cnt;

    eventfd_ctx_remove_wait_queue(virqfd->eventfd, &virqfd->wait, &cnt);
    flush_work(&virqfd->inject);
    eventfd_ctx_put(virqfd->eventfd);

    kfree(virqfd);
}

static void virqfd_inject(struct work_struct *work)
{
    struct virqfd *virqfd = container_of(work, struct virqfd, inject);
    if (virqfd->thread)
        virqfd->thread(virqfd->vdev, virqfd->data);
}

static int virqfd_enable(struct vfio_pci_device *vdev,
             int (*handler)(struct vfio_pci_device *, void *),
             void (*thread)(struct vfio_pci_device *, void *),
             void *data, struct virqfd **pvirqfd, int fd)
{
    struct file *file = NULL;
    struct eventfd_ctx *ctx = NULL;
    struct virqfd *virqfd;
    int ret = 0;
    unsigned int events;

    virqfd = kzalloc(sizeof(*virqfd), GFP_KERNEL);
    if (!virqfd)
        return -ENOMEM;

    virqfd->pvirqfd = pvirqfd;
    virqfd->vdev = vdev;
    virqfd->handler = handler;
    virqfd->thread = thread;
    virqfd->data = data;

    INIT_WORK(&virqfd->shutdown, virqfd_shutdown);
    INIT_WORK(&virqfd->inject, virqfd_inject);

    file = eventfd_fget(fd);
    if (IS_ERR(file)) {
        ret = PTR_ERR(file);
        goto fail;
    }

    ctx = eventfd_ctx_fileget(file);
    if (IS_ERR(ctx)) {
        ret = PTR_ERR(ctx);
        goto fail;
    }

    virqfd->eventfd = ctx;

    /*
     * virqfds can be released by closing the eventfd or directly
     * through ioctl.  These are both done through a workqueue, so
     * we update the pointer to the virqfd under lock to avoid
     * pushing multiple jobs to release the same virqfd.
     */
    spin_lock_irq(&vdev->irqlock);

    if (*pvirqfd) {
        spin_unlock_irq(&vdev->irqlock);
        ret = -EBUSY;
        goto fail;
    }
    *pvirqfd = virqfd;

    spin_unlock_irq(&vdev->irqlock);

    /*
     * Install our own custom wake-up handling so we are notified via
     * a callback whenever someone signals the underlying eventfd.
     */
    init_waitqueue_func_entry(&virqfd->wait, virqfd_wakeup);
    init_poll_funcptr(&virqfd->pt, virqfd_ptable_queue_proc);

    events = file->f_op->poll(file, &virqfd->pt);

    /*
     * Check if there was an event already pending on the eventfd
     * before we registered and trigger it as if we didn't miss it.
     */
    if (events & POLLIN) {
        if ((!handler || handler(vdev, data)) && thread)
            schedule_work(&virqfd->inject);
    }

    /*
     * Do not drop the file until the irqfd is fully initialized,
     * otherwise we might race against the POLLHUP.
     */
    fput(file);

    return 0;

fail:
    if (ctx && !IS_ERR(ctx))
        eventfd_ctx_put(ctx);

    if (file && !IS_ERR(file))
        fput(file);

    kfree(virqfd);

    return ret;
}

static void virqfd_disable(struct vfio_pci_device *vdev,
               struct virqfd **pvirqfd)
{
    unsigned long flags;

    spin_lock_irqsave(&vdev->irqlock, flags);

    if (*pvirqfd) {
        virqfd_deactivate(*pvirqfd);
        *pvirqfd = NULL;
    }

    spin_unlock_irqrestore(&vdev->irqlock, flags);

    /*
     * Block until we know all outstanding shutdown jobs have completed.
     * Even if we don't queue the job, flush the wq to be sure it's
     * been released.
     */
    flush_workqueue(vfio_irqfd_cleanup_wq);
}

/*
 * INTx
 */
static void vfio_send_intx_eventfd(struct vfio_pci_device *vdev, void *unused)
{
    if (likely(is_intx(vdev) && !vdev->virq_disabled))
        eventfd_signal(vdev->ctx[0].trigger, 1);
}

void vfio_pci_intx_mask(struct vfio_pci_device *vdev)
{
    struct pci_dev *pdev = vdev->pdev;
    unsigned long flags;

    spin_lock_irqsave(&vdev->irqlock, flags);

    /*
     * Masking can come from interrupt, ioctl, or config space
     * via INTx disable.  The latter means this can get called
     * even when not using intx delivery.  In this case, just
     * try to have the physical bit follow the virtual bit.
     */
    if (unlikely(!is_intx(vdev))) {
        if (vdev->pci_2_3)
            pci_intx(pdev, 0);
    } else if (!vdev->ctx[0].masked) {
        /*
         * Can't use check_and_mask here because we always want to
         * mask, not just when something is pending.
         */
        if (vdev->pci_2_3)
            pci_intx(pdev, 0);
        else
            disable_irq_nosync(pdev->irq);

        vdev->ctx[0].masked = true;
    }

    spin_unlock_irqrestore(&vdev->irqlock, flags);
}

/*
 * If this is triggered by an eventfd, we can't call eventfd_signal
 * or else we'll deadlock on the eventfd wait queue.  Return >0 when
 * a signal is necessary, which can then be handled via a work queue
 * or directly depending on the caller.
 */
int vfio_pci_intx_unmask_handler(struct vfio_pci_device *vdev, void *unused)
{
    struct pci_dev *pdev = vdev->pdev;
    unsigned long flags;
    int ret = 0;

    spin_lock_irqsave(&vdev->irqlock, flags);

    /*
     * Unmasking comes from ioctl or config, so again, have the
     * physical bit follow the virtual even when not using INTx.
     */
    if (unlikely(!is_intx(vdev))) {
        if (vdev->pci_2_3)
            pci_intx(pdev, 1);
    } else if (vdev->ctx[0].masked && !vdev->virq_disabled) {
        /*
         * A pending interrupt here would immediately trigger,
         * but we can avoid that overhead by just re-sending
         * the interrupt to the user.
         */
        if (vdev->pci_2_3) {
            if (!pci_check_and_unmask_intx(pdev))
                ret = 1;
        } else
            enable_irq(pdev->irq);

        vdev->ctx[0].masked = (ret > 0);
    }

    spin_unlock_irqrestore(&vdev->irqlock, flags);

    return ret;
}

void vfio_pci_intx_unmask(struct vfio_pci_device *vdev)
{
    if (vfio_pci_intx_unmask_handler(vdev, NULL) > 0)
        vfio_send_intx_eventfd(vdev, NULL);
}

static irqreturn_t vfio_intx_handler(int irq, void *dev_id)
{
    struct vfio_pci_device *vdev = dev_id;
    unsigned long flags;
    int ret = IRQ_NONE;

    spin_lock_irqsave(&vdev->irqlock, flags);

    if (!vdev->pci_2_3) {
        disable_irq_nosync(vdev->pdev->irq);
        vdev->ctx[0].masked = true;
        ret = IRQ_HANDLED;
    } else if (!vdev->ctx[0].masked &&  /* may be shared */
           pci_check_and_mask_intx(vdev->pdev)) {
        vdev->ctx[0].masked = true;
        ret = IRQ_HANDLED;
    }

    spin_unlock_irqrestore(&vdev->irqlock, flags);

    if (ret == IRQ_HANDLED)
        vfio_send_intx_eventfd(vdev, NULL);

    return ret;
}

static int vfio_intx_enable(struct vfio_pci_device *vdev)
{
    if (!is_irq_none(vdev))
        return -EINVAL;

    if (!vdev->pdev->irq)
        return -ENODEV;

    vdev->ctx = kzalloc(sizeof(struct vfio_pci_irq_ctx), GFP_KERNEL);
    if (!vdev->ctx)
        return -ENOMEM;

    vdev->num_ctx = 1;

    /*
     * If the virtual interrupt is masked, restore it.  Devices
     * supporting DisINTx can be masked at the hardware level
     * here, non-PCI-2.3 devices will have to wait until the
     * interrupt is enabled.
     */
    vdev->ctx[0].masked = vdev->virq_disabled;
    if (vdev->pci_2_3)
        pci_intx(vdev->pdev, !vdev->ctx[0].masked);

    vdev->irq_type = VFIO_PCI_INTX_IRQ_INDEX;

    return 0;
}

static int vfio_intx_set_signal(struct vfio_pci_device *vdev, int fd)
{
    struct pci_dev *pdev = vdev->pdev;
    unsigned long irqflags = IRQF_SHARED;
    struct eventfd_ctx *trigger;
    unsigned long flags;
    int ret;

    if (vdev->ctx[0].trigger) {
        free_irq(pdev->irq, vdev);
        kfree(vdev->ctx[0].name);
        eventfd_ctx_put(vdev->ctx[0].trigger);
        vdev->ctx[0].trigger = NULL;
    }

    if (fd < 0) /* Disable only */
        return 0;

    vdev->ctx[0].name = kasprintf(GFP_KERNEL, "vfio-intx(%s)",
                      pci_name(pdev));
    if (!vdev->ctx[0].name)
        return -ENOMEM;

    trigger = eventfd_ctx_fdget(fd);
    if (IS_ERR(trigger)) {
        kfree(vdev->ctx[0].name);
        return PTR_ERR(trigger);
    }

    vdev->ctx[0].trigger = trigger;

    if (!vdev->pci_2_3)
        irqflags = 0;

    ret = request_irq(pdev->irq, vfio_intx_handler,
              irqflags, vdev->ctx[0].name, vdev);
    if (ret) {
        vdev->ctx[0].trigger = NULL;
        kfree(vdev->ctx[0].name);
        eventfd_ctx_put(trigger);
        return ret;
    }

    /*
     * INTx disable will stick across the new irq setup,
     * disable_irq won't.
     */
    spin_lock_irqsave(&vdev->irqlock, flags);
    if (!vdev->pci_2_3 && vdev->ctx[0].masked)
        disable_irq_nosync(pdev->irq);
    spin_unlock_irqrestore(&vdev->irqlock, flags);

    return 0;
}

static void vfio_intx_disable(struct vfio_pci_device *vdev)
{
    vfio_intx_set_signal(vdev, -1);
    virqfd_disable(vdev, &vdev->ctx[0].unmask);
    virqfd_disable(vdev, &vdev->ctx[0].mask);
    vdev->irq_type = VFIO_PCI_NUM_IRQS;
    vdev->num_ctx = 0;
    kfree(vdev->ctx);
}

/*
 * MSI/MSI-X
 */
static irqreturn_t vfio_msihandler(int irq, void *arg)
{
    struct eventfd_ctx *trigger = arg;

    eventfd_signal(trigger, 1);
    return IRQ_HANDLED;
}

static int vfio_msi_enable(struct vfio_pci_device *vdev, int nvec, bool msix)
{
    struct pci_dev *pdev = vdev->pdev;
    int ret;

    if (!is_irq_none(vdev))
        return -EINVAL;

    vdev->ctx = kzalloc(nvec * sizeof(struct vfio_pci_irq_ctx), GFP_KERNEL);
    if (!vdev->ctx)
        return -ENOMEM;

    if (msix) {
        int i;

        vdev->msix = kzalloc(nvec * sizeof(struct msix_entry),
                     GFP_KERNEL);
        if (!vdev->msix) {
            kfree(vdev->ctx);
            return -ENOMEM;
        }

        for (i = 0; i < nvec; i++)
            vdev->msix[i].entry = i;

        ret = pci_enable_msix(pdev, vdev->msix, nvec);
        if (ret) {
            kfree(vdev->msix);
            kfree(vdev->ctx);
            return ret;
        }
    } else {
        ret = pci_enable_msi_block(pdev, nvec);
        if (ret) {
            kfree(vdev->ctx);
            return ret;
        }
    }

    vdev->num_ctx = nvec;
    vdev->irq_type = msix ? VFIO_PCI_MSIX_IRQ_INDEX :
                VFIO_PCI_MSI_IRQ_INDEX;

    if (!msix) {
        /*
         * Compute the virtual hardware field for max msi vectors -
         * it is the log base 2 of the number of vectors.
         */
        vdev->msi_qmax = fls(nvec * 2 - 1) - 1;
    }

    return 0;
}

static int vfio_msi_set_vector_signal(struct vfio_pci_device *vdev,
                      int vector, int fd, bool msix)
{
    struct pci_dev *pdev = vdev->pdev;
    int irq = msix ? vdev->msix[vector].vector : pdev->irq + vector;
    char *name = msix ? "vfio-msix" : "vfio-msi";
    struct eventfd_ctx *trigger;
    int ret;

    if (vector >= vdev->num_ctx)
        return -EINVAL;

    if (vdev->ctx[vector].trigger) {
        free_irq(irq, vdev->ctx[vector].trigger);
        kfree(vdev->ctx[vector].name);
        eventfd_ctx_put(vdev->ctx[vector].trigger);
        vdev->ctx[vector].trigger = NULL;
    }

    if (fd < 0)
        return 0;

    vdev->ctx[vector].name = kasprintf(GFP_KERNEL, "%s[%d](%s)",
                       name, vector, pci_name(pdev));
    if (!vdev->ctx[vector].name)
        return -ENOMEM;

    trigger = eventfd_ctx_fdget(fd);
    if (IS_ERR(trigger)) {
        kfree(vdev->ctx[vector].name);
        return PTR_ERR(trigger);
    }

    ret = request_irq(irq, vfio_msihandler, 0,
              vdev->ctx[vector].name, trigger);
    if (ret) {
        kfree(vdev->ctx[vector].name);
        eventfd_ctx_put(trigger);
        return ret;
    }

    vdev->ctx[vector].trigger = trigger;

    return 0;
}

static int vfio_msi_set_block(struct vfio_pci_device *vdev, unsigned start,
                  unsigned count, int32_t *fds, bool msix)
{
    int i, j, ret = 0;

    if (start + count > vdev->num_ctx)
        return -EINVAL;

    for (i = 0, j = start; i < count && !ret; i++, j++) {
        int fd = fds ? fds[i] : -1;
        ret = vfio_msi_set_vector_signal(vdev, j, fd, msix);
    }

    if (ret) {
        for (--j; j >= start; j--)
            vfio_msi_set_vector_signal(vdev, j, -1, msix);
    }

    return ret;
}

static void vfio_msi_disable(struct vfio_pci_device *vdev, bool msix)
{
    struct pci_dev *pdev = vdev->pdev;
    int i;

    vfio_msi_set_block(vdev, 0, vdev->num_ctx, NULL, msix);

    for (i = 0; i < vdev->num_ctx; i++) {
        virqfd_disable(vdev, &vdev->ctx[i].unmask);
        virqfd_disable(vdev, &vdev->ctx[i].mask);
    }

    if (msix) {
        pci_disable_msix(vdev->pdev);
        kfree(vdev->msix);
    } else
        pci_disable_msi(pdev);

    vdev->irq_type = VFIO_PCI_NUM_IRQS;
    vdev->num_ctx = 0;
    kfree(vdev->ctx);
}

/*
 * IOCTL support
 */
static int vfio_pci_set_intx_unmask(struct vfio_pci_device *vdev,
                    unsigned index, unsigned start,
                    unsigned count, uint32_t flags, void *data)
{
    if (!is_intx(vdev) || start != 0 || count != 1)
        return -EINVAL;

    if (flags & VFIO_IRQ_SET_DATA_NONE) {
        vfio_pci_intx_unmask(vdev);
    } else if (flags & VFIO_IRQ_SET_DATA_BOOL) {
        uint8_t unmask = *(uint8_t *)data;
        if (unmask)
            vfio_pci_intx_unmask(vdev);
    } else if (flags & VFIO_IRQ_SET_DATA_EVENTFD) {
        int32_t fd = *(int32_t *)data;
        if (fd >= 0)
            return virqfd_enable(vdev, vfio_pci_intx_unmask_handler,
                         vfio_send_intx_eventfd, NULL,
                         &vdev->ctx[0].unmask, fd);

        virqfd_disable(vdev, &vdev->ctx[0].unmask);
    }

    return 0;
}

static int vfio_pci_set_intx_mask(struct vfio_pci_device *vdev,
                  unsigned index, unsigned start,
                  unsigned count, uint32_t flags, void *data)
{
    if (!is_intx(vdev) || start != 0 || count != 1)
        return -EINVAL;

    if (flags & VFIO_IRQ_SET_DATA_NONE) {
        vfio_pci_intx_mask(vdev);
    } else if (flags & VFIO_IRQ_SET_DATA_BOOL) {
        uint8_t mask = *(uint8_t *)data;
        if (mask)
            vfio_pci_intx_mask(vdev);
    } else if (flags & VFIO_IRQ_SET_DATA_EVENTFD) {
        return -ENOTTY; /* XXX implement me */
    }

    return 0;
}

static int vfio_pci_set_intx_trigger(struct vfio_pci_device *vdev,
                     unsigned index, unsigned start,
                     unsigned count, uint32_t flags, void *data)
{
    if (is_intx(vdev) && !count && (flags & VFIO_IRQ_SET_DATA_NONE)) {
        vfio_intx_disable(vdev);
        return 0;
    }

    if (!(is_intx(vdev) || is_irq_none(vdev)) || start != 0 || count != 1)
        return -EINVAL;

    if (flags & VFIO_IRQ_SET_DATA_EVENTFD) {
        int32_t fd = *(int32_t *)data;
        int ret;

        if (is_intx(vdev))
            return vfio_intx_set_signal(vdev, fd);

        ret = vfio_intx_enable(vdev);
        if (ret)
            return ret;

        ret = vfio_intx_set_signal(vdev, fd);
        if (ret)
            vfio_intx_disable(vdev);

        return ret;
    }

    if (!is_intx(vdev))
        return -EINVAL;

    if (flags & VFIO_IRQ_SET_DATA_NONE) {
        vfio_send_intx_eventfd(vdev, NULL);
    } else if (flags & VFIO_IRQ_SET_DATA_BOOL) {
        uint8_t trigger = *(uint8_t *)data;
        if (trigger)
            vfio_send_intx_eventfd(vdev, NULL);
    }
    return 0;
}

static int vfio_pci_set_msi_trigger(struct vfio_pci_device *vdev,
                    unsigned index, unsigned start,
                    unsigned count, uint32_t flags, void *data)
{
    int i;
    bool msix = (index == VFIO_PCI_MSIX_IRQ_INDEX) ? true : false;

    if (irq_is(vdev, index) && !count && (flags & VFIO_IRQ_SET_DATA_NONE)) {
        vfio_msi_disable(vdev, msix);
        return 0;
    }

    if (!(irq_is(vdev, index) || is_irq_none(vdev)))
        return -EINVAL;

    if (flags & VFIO_IRQ_SET_DATA_EVENTFD) {
        int32_t *fds = data;
        int ret;

        if (vdev->irq_type == index)
            return vfio_msi_set_block(vdev, start, count,
                          fds, msix);

        ret = vfio_msi_enable(vdev, start + count, msix);
        if (ret)
            return ret;

        ret = vfio_msi_set_block(vdev, start, count, fds, msix);
        if (ret)
            vfio_msi_disable(vdev, msix);

        return ret;
    }

    if (!irq_is(vdev, index) || start + count > vdev->num_ctx)
        return -EINVAL;

    for (i = start; i < start + count; i++) {
        if (!vdev->ctx[i].trigger)
            continue;
        if (flags & VFIO_IRQ_SET_DATA_NONE) {
            eventfd_signal(vdev->ctx[i].trigger, 1);
        } else if (flags & VFIO_IRQ_SET_DATA_BOOL) {
            uint8_t *bools = data;
            if (bools[i - start])
                eventfd_signal(vdev->ctx[i].trigger, 1);
        }
    }
    return 0;
}

int vfio_pci_set_irqs_ioctl(struct vfio_pci_device *vdev, uint32_t flags,
                unsigned index, unsigned start, unsigned count,
                void *data)
{
    int (*func)(struct vfio_pci_device *vdev, unsigned index,
            unsigned start, unsigned count, uint32_t flags,
            void *data) = NULL;

    switch (index) {
    case VFIO_PCI_INTX_IRQ_INDEX:
        switch (flags & VFIO_IRQ_SET_ACTION_TYPE_MASK) {
        case VFIO_IRQ_SET_ACTION_MASK:
            func = vfio_pci_set_intx_mask;
            break;
        case VFIO_IRQ_SET_ACTION_UNMASK:
            func = vfio_pci_set_intx_unmask;
            break;
        case VFIO_IRQ_SET_ACTION_TRIGGER:
            func = vfio_pci_set_intx_trigger;
            break;
        }
        break;
    case VFIO_PCI_MSI_IRQ_INDEX:
    case VFIO_PCI_MSIX_IRQ_INDEX:
        switch (flags & VFIO_IRQ_SET_ACTION_TYPE_MASK) {
        case VFIO_IRQ_SET_ACTION_MASK:
        case VFIO_IRQ_SET_ACTION_UNMASK:
            /* XXX Need masking support exported */
            break;
        case VFIO_IRQ_SET_ACTION_TRIGGER:
            func = vfio_pci_set_msi_trigger;
            break;
        }
        break;
    }

    if (!func)
        return -ENOTTY;

    return func(vdev, index, start, count, flags, data);
}