Commit 7d37d351 authored by Jan Kiszka's avatar Jan Kiszka Committed by Avi Kivity
Browse files

virtio/vhost: Add support for KVM in-kernel MSI injection 



Make use of the new vector notifier to track changes of the MSI-X
configuration of virtio PCI devices. On enabling events, we establish
the required virtual IRQ to MSI-X message route and link the signaling
eventfd file descriptor to this vIRQ line. That way, vhost-generated
interrupts can be directly delivered to an in-kernel MSI-X consumer like
the x86 APIC.

Signed-off-by: default avatarJan Kiszka <jan.kiszka@siemens.com>
Signed-off-by: default avatarAvi Kivity <avi@redhat.com>
parent cb697aaa

hw/virtio-pci.c

+126 −0
Original line number Diff line number Diff line
@@ -24,6 +24,7 @@ 
#include "virtio-scsi.h"

#include "pci.h"

#include "qemu-error.h"

#include "msi.h"

#include "msix.h"

#include "net.h"

#include "loader.h"
@@ -539,6 +540,107 @@ static void virtio_pci_guest_notifier_read(void *opaque) 
    }

}



static int kvm_virtio_pci_vq_vector_use(VirtIOPCIProxy *proxy,

                                        unsigned int queue_no,

                                        unsigned int vector,

                                        MSIMessage msg)

{

    VirtQueue *vq = virtio_get_queue(proxy->vdev, queue_no);

    VirtIOIRQFD *irqfd = &proxy->vector_irqfd[vector];

    int fd, ret;



    fd = event_notifier_get_fd(virtio_queue_get_guest_notifier(vq));



    if (irqfd->users == 0) {

        ret = kvm_irqchip_add_msi_route(kvm_state, msg);

        if (ret < 0) {

            return ret;

        }

        irqfd->virq = ret;

    }

    irqfd->users++;



    ret = kvm_irqchip_add_irqfd(kvm_state, fd, irqfd->virq);

    if (ret < 0) {

        if (--irqfd->users == 0) {

            kvm_irqchip_release_virq(kvm_state, irqfd->virq);

        }

        return ret;

    }



    qemu_set_fd_handler(fd, NULL, NULL, NULL);



    return 0;

}



static void kvm_virtio_pci_vq_vector_release(VirtIOPCIProxy *proxy,

                                             unsigned int queue_no,

                                             unsigned int vector)

{

    VirtQueue *vq = virtio_get_queue(proxy->vdev, queue_no);

    VirtIOIRQFD *irqfd = &proxy->vector_irqfd[vector];

    int fd, ret;



    fd = event_notifier_get_fd(virtio_queue_get_guest_notifier(vq));



    ret = kvm_irqchip_remove_irqfd(kvm_state, fd, irqfd->virq);

    assert(ret == 0);



    if (--irqfd->users == 0) {

        kvm_irqchip_release_virq(kvm_state, irqfd->virq);

    }



    qemu_set_fd_handler(fd, virtio_pci_guest_notifier_read, NULL, vq);

}



static int kvm_virtio_pci_vector_use(PCIDevice *dev, unsigned vector,

                                     MSIMessage msg)

{

    VirtIOPCIProxy *proxy = container_of(dev, VirtIOPCIProxy, pci_dev);

    VirtIODevice *vdev = proxy->vdev;

    int ret, queue_no;



    for (queue_no = 0; queue_no < VIRTIO_PCI_QUEUE_MAX; queue_no++) {

        if (!virtio_queue_get_num(vdev, queue_no)) {

            break;

        }

        if (virtio_queue_vector(vdev, queue_no) != vector) {

            continue;

        }

        ret = kvm_virtio_pci_vq_vector_use(proxy, queue_no, vector, msg);

        if (ret < 0) {

            goto undo;

        }

    }

    return 0;



undo:

    while (--queue_no >= 0) {

        if (virtio_queue_vector(vdev, queue_no) != vector) {

            continue;

        }

        kvm_virtio_pci_vq_vector_release(proxy, queue_no, vector);

    }

    return ret;

}



static void kvm_virtio_pci_vector_release(PCIDevice *dev, unsigned vector)

{

    VirtIOPCIProxy *proxy = container_of(dev, VirtIOPCIProxy, pci_dev);

    VirtIODevice *vdev = proxy->vdev;

    int queue_no;



    for (queue_no = 0; queue_no < VIRTIO_PCI_QUEUE_MAX; queue_no++) {

        if (!virtio_queue_get_num(vdev, queue_no)) {

            break;

        }

        if (virtio_queue_vector(vdev, queue_no) != vector) {

            continue;

        }

        kvm_virtio_pci_vq_vector_release(proxy, queue_no, vector);

    }

}



static int virtio_pci_set_guest_notifier(void *opaque, int n, bool assign)

{

    VirtIOPCIProxy *proxy = opaque;
@@ -555,6 +657,9 @@ static int virtio_pci_set_guest_notifier(void *opaque, int n, bool assign) 
    } else {

        qemu_set_fd_handler(event_notifier_get_fd(notifier),

                            NULL, NULL, NULL);

        /* Test and clear notifier before closing it,

         * in case poll callback didn't have time to run. */

        virtio_pci_guest_notifier_read(vq);

        event_notifier_cleanup(notifier);

    }
@@ -573,6 +678,13 @@ static int virtio_pci_set_guest_notifiers(void *opaque, bool assign) 
    VirtIODevice *vdev = proxy->vdev;

    int r, n;



    /* Must unset vector notifier while guest notifier is still assigned */

    if (kvm_irqchip_in_kernel() && !assign) {

        msix_unset_vector_notifiers(&proxy->pci_dev);

        g_free(proxy->vector_irqfd);

        proxy->vector_irqfd = NULL;

    }



    for (n = 0; n < VIRTIO_PCI_QUEUE_MAX; n++) {

        if (!virtio_queue_get_num(vdev, n)) {

            break;
@@ -584,10 +696,24 @@ static int virtio_pci_set_guest_notifiers(void *opaque, bool assign) 
        }

    }



    /* Must set vector notifier after guest notifier has been assigned */

    if (kvm_irqchip_in_kernel() && assign) {

        proxy->vector_irqfd =

            g_malloc0(sizeof(*proxy->vector_irqfd) *

                      msix_nr_vectors_allocated(&proxy->pci_dev));

        r = msix_set_vector_notifiers(&proxy->pci_dev,

                                      kvm_virtio_pci_vector_use,

                                      kvm_virtio_pci_vector_release);

        if (r < 0) {

            goto assign_error;

        }

    }



    return 0;



assign_error:

    /* We get here on assignment failure. Recover by undoing for VQs 0 .. n. */

    assert(assign);

    while (--n >= 0) {

        virtio_pci_set_guest_notifier(opaque, n, !assign);

    }

hw/virtio-pci.h

+6 −0
Original line number Diff line number Diff line
@@ -24,6 +24,11 @@ 
#define VIRTIO_PCI_FLAG_USE_IOEVENTFD_BIT 1

#define VIRTIO_PCI_FLAG_USE_IOEVENTFD   (1 << VIRTIO_PCI_FLAG_USE_IOEVENTFD_BIT)



typedef struct {

    int virq;

    unsigned int users;

} VirtIOIRQFD;



typedef struct {

    PCIDevice pci_dev;

    VirtIODevice *vdev;
@@ -44,6 +49,7 @@ typedef struct { 
    VirtIOSCSIConf scsi;

    bool ioeventfd_disabled;

    bool ioeventfd_started;

    VirtIOIRQFD *vector_irqfd;

} VirtIOPCIProxy;



void virtio_init_pci(VirtIOPCIProxy *proxy, VirtIODevice *vdev);