Commit b0e5d90e authored by Cornelia Huck's avatar Cornelia Huck Committed by Stefan Hajnoczi
Browse files

dataplane: endianness-aware accesses 



The vring.c code currently assumes that guest and host endianness match,
which is not true for a number of cases:

- emulating targets with a different endianness than the host
- bi-endian targets, where the correct endianness depends on the virtio
  device
- upcoming support for the virtio-1 standard mandates little-endian
  accesses even for big-endian targets and hosts

Make sure to use accessors that depend on the virtio device.

Note that dataplane now needs to be built per-target.

Cc: Stefan Hajnoczi <stefanha@redhat.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Fam Zheng <famz@redhat.com>
Reviewed-by: default avatarDavid Gibson <david@gibson.dropbear.id.au>
Tested-by: default avatarDavid Gibson <david@gibson.dropbear.id.au>
Signed-off-by: default avatarCornelia Huck <cornelia.huck@de.ibm.com>
Reviewed-by: default avatarStefan Hajnoczi <stefanha@redhat.com>
Message-id: 1422289602-17874-2-git-send-email-cornelia.huck@de.ibm.com
Signed-off-by: default avatarStefan Hajnoczi <stefanha@redhat.com>
parent 9a75b0a0

hw/block/dataplane/virtio-blk.c

+3 −1
Original line number Diff line number Diff line
@@ -16,7 +16,9 @@ 
#include "qemu/iov.h"

#include "qemu/thread.h"

#include "qemu/error-report.h"

#include "hw/virtio/virtio-access.h"

#include "hw/virtio/dataplane/vring.h"

#include "hw/virtio/dataplane/vring-accessors.h"

#include "sysemu/block-backend.h"

#include "hw/virtio/virtio-blk.h"

#include "virtio-blk.h"
@@ -75,7 +77,7 @@ static void complete_request_vring(VirtIOBlockReq *req, unsigned char status) 
    VirtIOBlockDataPlane *s = req->dev->dataplane;

    stb_p(&req->in->status, status);



    vring_push(&req->dev->dataplane->vring, &req->elem,

    vring_push(s->vdev, &req->dev->dataplane->vring, &req->elem,

               req->qiov.size + sizeof(*req->in));



    /* Suppress notification to guest by BH and its scheduled

hw/scsi/virtio-scsi-dataplane.c

+1 −1
Original line number Diff line number Diff line
@@ -94,7 +94,7 @@ void virtio_scsi_vring_push_notify(VirtIOSCSIReq *req) 
{

    VirtIODevice *vdev = VIRTIO_DEVICE(req->vring->parent);



    vring_push(&req->vring->vring, &req->elem,

    vring_push(vdev, &req->vring->vring, &req->elem,

               req->qsgl.size + req->resp_iov.size);



    if (vring_should_notify(vdev, &req->vring->vring)) {

hw/virtio/Makefile.objs

+1 −1
Original line number Diff line number Diff line
@@ -2,7 +2,7 @@ common-obj-y += virtio-rng.o 
common-obj-$(CONFIG_VIRTIO_PCI) += virtio-pci.o

common-obj-y += virtio-bus.o

common-obj-y += virtio-mmio.o

common-obj-$(CONFIG_VIRTIO) += dataplane/

obj-$(CONFIG_VIRTIO) += dataplane/



obj-y += virtio.o virtio-balloon.o 

obj-$(CONFIG_LINUX) += vhost.o vhost-backend.o vhost-user.o

hw/virtio/dataplane/Makefile.objs

+1 −1
Original line number Diff line number Diff line 
common-obj-y += vring.o
 
obj-y += vring.o

hw/virtio/dataplane/vring.c

+34 −19
Original line number Diff line number Diff line
@@ -18,7 +18,9 @@ 
#include "hw/hw.h"

#include "exec/memory.h"

#include "exec/address-spaces.h"

#include "hw/virtio/virtio-access.h"

#include "hw/virtio/dataplane/vring.h"

#include "hw/virtio/dataplane/vring-accessors.h"

#include "qemu/error-report.h"



/* vring_map can be coupled with vring_unmap or (if you still have the
@@ -83,7 +85,7 @@ bool vring_setup(Vring *vring, VirtIODevice *vdev, int n) 
    vring_init(&vring->vr, virtio_queue_get_num(vdev, n), vring_ptr, 4096);



    vring->last_avail_idx = virtio_queue_get_last_avail_idx(vdev, n);

    vring->last_used_idx = vring->vr.used->idx;

    vring->last_used_idx = vring_get_used_idx(vdev, vring);

    vring->signalled_used = 0;

    vring->signalled_used_valid = false;
@@ -104,7 +106,7 @@ void vring_teardown(Vring *vring, VirtIODevice *vdev, int n) 
void vring_disable_notification(VirtIODevice *vdev, Vring *vring)

{

    if (!(vdev->guest_features & (1 << VIRTIO_RING_F_EVENT_IDX))) {

        vring->vr.used->flags |= VRING_USED_F_NO_NOTIFY;

        vring_set_used_flags(vdev, vring, VRING_USED_F_NO_NOTIFY);

    }

}
@@ -117,10 +119,10 @@ bool vring_enable_notification(VirtIODevice *vdev, Vring *vring) 
    if (vdev->guest_features & (1 << VIRTIO_RING_F_EVENT_IDX)) {

        vring_avail_event(&vring->vr) = vring->vr.avail->idx;

    } else {

        vring->vr.used->flags &= ~VRING_USED_F_NO_NOTIFY;

        vring_clear_used_flags(vdev, vring, VRING_USED_F_NO_NOTIFY);

    }

    smp_mb(); /* ensure update is seen before reading avail_idx */

    return !vring_more_avail(vring);

    return !vring_more_avail(vdev, vring);

}



/* This is stolen from linux/drivers/vhost/vhost.c:vhost_notify() */
@@ -134,12 +136,13 @@ bool vring_should_notify(VirtIODevice *vdev, Vring *vring) 
    smp_mb();



    if ((vdev->guest_features & (1 << VIRTIO_F_NOTIFY_ON_EMPTY)) &&

        unlikely(vring->vr.avail->idx == vring->last_avail_idx)) {

        unlikely(!vring_more_avail(vdev, vring))) {

        return true;

    }



    if (!(vdev->guest_features & (1 << VIRTIO_RING_F_EVENT_IDX))) {

        return !(vring->vr.avail->flags & VRING_AVAIL_F_NO_INTERRUPT);

        return !(vring_get_avail_flags(vdev, vring) &

                 VRING_AVAIL_F_NO_INTERRUPT);

    }

    old = vring->signalled_used;

    v = vring->signalled_used_valid;
@@ -202,9 +205,19 @@ static int get_desc(Vring *vring, VirtQueueElement *elem, 
    return 0;

}



static void copy_in_vring_desc(VirtIODevice *vdev,

                               const struct vring_desc *guest,

                               struct vring_desc *host)

{

    host->addr = virtio_ldq_p(vdev, &guest->addr);

    host->len = virtio_ldl_p(vdev, &guest->len);

    host->flags = virtio_lduw_p(vdev, &guest->flags);

    host->next = virtio_lduw_p(vdev, &guest->next);

}



/* This is stolen from linux/drivers/vhost/vhost.c. */

static int get_indirect(Vring *vring, VirtQueueElement *elem,

                        struct vring_desc *indirect)

static int get_indirect(VirtIODevice *vdev, Vring *vring,

                        VirtQueueElement *elem, struct vring_desc *indirect)

{

    struct vring_desc desc;

    unsigned int i = 0, count, found = 0;
@@ -244,7 +257,7 @@ static int get_indirect(Vring *vring, VirtQueueElement *elem, 
            vring->broken = true;

            return -EFAULT;

        }

        desc = *desc_ptr;

        copy_in_vring_desc(vdev, desc_ptr, &desc);

        memory_region_unref(mr);



        /* Ensure descriptor has been loaded before accessing fields */
@@ -320,7 +333,7 @@ int vring_pop(VirtIODevice *vdev, Vring *vring, 


    /* Check it isn't doing very strange things with descriptor numbers. */

    last_avail_idx = vring->last_avail_idx;

    avail_idx = vring->vr.avail->idx;

    avail_idx = vring_get_avail_idx(vdev, vring);

    barrier(); /* load indices now and not again later */



    if (unlikely((uint16_t)(avail_idx - last_avail_idx) > num)) {
@@ -341,7 +354,7 @@ int vring_pop(VirtIODevice *vdev, Vring *vring, 


    /* Grab the next descriptor number they're advertising, and increment

     * the index we've seen. */

    head = vring->vr.avail->ring[last_avail_idx % num];

    head = vring_get_avail_ring(vdev, vring, last_avail_idx % num);



    elem->index = head;
@@ -365,13 +378,13 @@ int vring_pop(VirtIODevice *vdev, Vring *vring, 
            ret = -EFAULT;

            goto out;

        }

        desc = vring->vr.desc[i];

        copy_in_vring_desc(vdev, &vring->vr.desc[i], &desc);



        /* Ensure descriptor is loaded before accessing fields */

        barrier();



        if (desc.flags & VRING_DESC_F_INDIRECT) {

            ret = get_indirect(vring, elem, &desc);

            ret = get_indirect(vdev, vring, elem, &desc);

            if (ret < 0) {

                goto out;

            }
@@ -407,9 +420,9 @@ out: 
 *

 * Stolen from linux/drivers/vhost/vhost.c.

 */

void vring_push(Vring *vring, VirtQueueElement *elem, int len)

void vring_push(VirtIODevice *vdev, Vring *vring, VirtQueueElement *elem,

                int len)

{

    struct vring_used_elem *used;

    unsigned int head = elem->index;

    uint16_t new;
@@ -422,14 +435,16 @@ void vring_push(Vring *vring, VirtQueueElement *elem, int len) 


    /* The virtqueue contains a ring of used buffers.  Get a pointer to the

     * next entry in that used ring. */

    used = &vring->vr.used->ring[vring->last_used_idx % vring->vr.num];

    used->id = head;

    used->len = len;

    vring_set_used_ring_id(vdev, vring, vring->last_used_idx % vring->vr.num,

                           head);

    vring_set_used_ring_len(vdev, vring, vring->last_used_idx % vring->vr.num,

                            len);



    /* Make sure buffer is written before we update index. */

    smp_wmb();



    new = vring->vr.used->idx = ++vring->last_used_idx;

    new = ++vring->last_used_idx;

    vring_set_used_idx(vdev, vring, new);

    if (unlikely((int16_t)(new - vring->signalled_used) < (uint16_t)1)) {

        vring->signalled_used_valid = false;

    }