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virtio: Support transports which can specify the vring alignment 

Support virtio transports which can specify the vring alignment
(ie where the guest communicates this to the host) by providing
a new virtio_queue_set_align() function. (The default alignment
remains as before.)

Transports which wish to make use of this must set the
has_variable_vring_alignment field in their VirtioBusClass
struct to true; they can then change the alignment via
virtio_queue_set_align().

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Message-id: 1373977512-28932-5-git-send-email-peter.maydell@linaro.org
This commit is contained in:
Peter Maydell 2013-07-16 13:25:08 +01:00
parent e63c0ba1bc
commit 6ce69d1c77
3 changed files with 36 additions and 3 deletions
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32
hw/virtio/virtio.c
View File

@ -19,8 +19,11 @@
#include "qemu/atomic.h"
#include "hw/virtio/virtio-bus.h"
/* The alignment to use between consumer and producer parts of vring.
* x86 pagesize again. */
/*
* The alignment to use between consumer and producer parts of vring.
* x86 pagesize again. This is the default, used by transports like PCI
* which don't provide a means for the guest to tell the host the alignment.
*/
#define VIRTIO_PCI_VRING_ALIGN 4096
typedef struct VRingDesc
@ -54,6 +57,7 @@ typedef struct VRingUsed
typedef struct VRing
{
unsigned int num;
unsigned int align;
hwaddr desc;
hwaddr avail;
hwaddr used;
@ -93,7 +97,7 @@ static void virtqueue_init(VirtQueue *vq)
vq->vring.avail = pa + vq->vring.num * sizeof(VRingDesc);
vq->vring.used = vring_align(vq->vring.avail +
offsetof(VRingAvail, ring[vq->vring.num]),
VIRTIO_PCI_VRING_ALIGN);
vq->vring.align);
}
static inline uint64_t vring_desc_addr(hwaddr desc_pa, int i)
@ -687,6 +691,21 @@ int virtio_queue_get_id(VirtQueue *vq)
return vq - &vdev->vq[0];
}
void virtio_queue_set_align(VirtIODevice *vdev, int n, int align)
{
BusState *qbus = qdev_get_parent_bus(DEVICE(vdev));
VirtioBusClass *k = VIRTIO_BUS_GET_CLASS(qbus);
/* Check that the transport told us it was going to do this
* (so a buggy transport will immediately assert rather than
* silently failing to migrate this state)
*/
assert(k->has_variable_vring_alignment);
vdev->vq[n].vring.align = align;
virtqueue_init(&vdev->vq[n]);
}
void virtio_queue_notify_vq(VirtQueue *vq)
{
if (vq->vring.desc) {
@ -727,6 +746,7 @@ VirtQueue *virtio_add_queue(VirtIODevice *vdev, int queue_size,
abort();
vdev->vq[i].vring.num = queue_size;
vdev->vq[i].vring.align = VIRTIO_PCI_VRING_ALIGN;
vdev->vq[i].handle_output = handle_output;
return &vdev->vq[i];
@ -833,6 +853,9 @@ void virtio_save(VirtIODevice *vdev, QEMUFile *f)
break;
qemu_put_be32(f, vdev->vq[i].vring.num);
if (k->has_variable_vring_alignment) {
qemu_put_be32(f, vdev->vq[i].vring.align);
}
qemu_put_be64(f, vdev->vq[i].pa);
qemu_put_be16s(f, &vdev->vq[i].last_avail_idx);
if (k->save_queue) {
@ -889,6 +912,9 @@ int virtio_load(VirtIODevice *vdev, QEMUFile *f)
for (i = 0; i < num; i++) {
vdev->vq[i].vring.num = qemu_get_be32(f);
if (k->has_variable_vring_alignment) {
vdev->vq[i].vring.align = qemu_get_be32(f);
}
vdev->vq[i].pa = qemu_get_be64(f);
qemu_get_be16s(f, &vdev->vq[i].last_avail_idx);
vdev->vq[i].signalled_used_valid = false;

6
include/hw/virtio/virtio-bus.h
View File

@ -62,6 +62,12 @@ typedef struct VirtioBusClass {
* This is called by virtio-bus just before the device is unplugged.
*/
void (*device_unplug)(DeviceState *d);
/*
* Does the transport have variable vring alignment?
* (ie can it ever call virtio_queue_set_align()?)
* Note that changing this will break migration for this transport.
*/
bool has_variable_vring_alignment;
} VirtioBusClass;
struct VirtioBusState {

1
include/hw/virtio/virtio.h
View File

@ -202,6 +202,7 @@ void virtio_queue_set_addr(VirtIODevice *vdev, int n, hwaddr addr);
hwaddr virtio_queue_get_addr(VirtIODevice *vdev, int n);
void virtio_queue_set_num(VirtIODevice *vdev, int n, int num);
int virtio_queue_get_num(VirtIODevice *vdev, int n);
void virtio_queue_set_align(VirtIODevice *vdev, int n, int align);
void virtio_queue_notify(VirtIODevice *vdev, int n);
uint16_t virtio_queue_vector(VirtIODevice *vdev, int n);
void virtio_queue_set_vector(VirtIODevice *vdev, int n, uint16_t vector);