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: David Gibson <david@gibson.dropbear.id.au>
Tested-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Cornelia Huck <cornelia.huck@de.ibm.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Message-id: 1422289602-17874-2-git-send-email-cornelia.huck@de.ibm.com
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
This commit is contained in:
Cornelia Huck 2015-01-26 17:26:42 +01:00 committed by Stefan Hajnoczi
parent 9a75b0a037
commit b0e5d90ebc
7 changed files with 117 additions and 35 deletions

View File

@ -16,7 +16,9 @@
#include "qemu/iov.h" #include "qemu/iov.h"
#include "qemu/thread.h" #include "qemu/thread.h"
#include "qemu/error-report.h" #include "qemu/error-report.h"
#include "hw/virtio/virtio-access.h"
#include "hw/virtio/dataplane/vring.h" #include "hw/virtio/dataplane/vring.h"
#include "hw/virtio/dataplane/vring-accessors.h"
#include "sysemu/block-backend.h" #include "sysemu/block-backend.h"
#include "hw/virtio/virtio-blk.h" #include "hw/virtio/virtio-blk.h"
#include "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; VirtIOBlockDataPlane *s = req->dev->dataplane;
stb_p(&req->in->status, status); 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)); req->qiov.size + sizeof(*req->in));
/* Suppress notification to guest by BH and its scheduled /* Suppress notification to guest by BH and its scheduled

View File

@ -94,7 +94,7 @@ void virtio_scsi_vring_push_notify(VirtIOSCSIReq *req)
{ {
VirtIODevice *vdev = VIRTIO_DEVICE(req->vring->parent); 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); req->qsgl.size + req->resp_iov.size);
if (vring_should_notify(vdev, &req->vring->vring)) { if (vring_should_notify(vdev, &req->vring->vring)) {

View File

@ -2,7 +2,7 @@ common-obj-y += virtio-rng.o
common-obj-$(CONFIG_VIRTIO_PCI) += virtio-pci.o common-obj-$(CONFIG_VIRTIO_PCI) += virtio-pci.o
common-obj-y += virtio-bus.o common-obj-y += virtio-bus.o
common-obj-y += virtio-mmio.o common-obj-y += virtio-mmio.o
common-obj-$(CONFIG_VIRTIO) += dataplane/ obj-$(CONFIG_VIRTIO) += dataplane/
obj-y += virtio.o virtio-balloon.o obj-y += virtio.o virtio-balloon.o
obj-$(CONFIG_LINUX) += vhost.o vhost-backend.o vhost-user.o obj-$(CONFIG_LINUX) += vhost.o vhost-backend.o vhost-user.o

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@ -1 +1 @@
common-obj-y += vring.o obj-y += vring.o

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@ -18,7 +18,9 @@
#include "hw/hw.h" #include "hw/hw.h"
#include "exec/memory.h" #include "exec/memory.h"
#include "exec/address-spaces.h" #include "exec/address-spaces.h"
#include "hw/virtio/virtio-access.h"
#include "hw/virtio/dataplane/vring.h" #include "hw/virtio/dataplane/vring.h"
#include "hw/virtio/dataplane/vring-accessors.h"
#include "qemu/error-report.h" #include "qemu/error-report.h"
/* vring_map can be coupled with vring_unmap or (if you still have the /* 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_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_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 = 0;
vring->signalled_used_valid = false; 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) void vring_disable_notification(VirtIODevice *vdev, Vring *vring)
{ {
if (!(vdev->guest_features & (1 << VIRTIO_RING_F_EVENT_IDX))) { 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)) { if (vdev->guest_features & (1 << VIRTIO_RING_F_EVENT_IDX)) {
vring_avail_event(&vring->vr) = vring->vr.avail->idx; vring_avail_event(&vring->vr) = vring->vr.avail->idx;
} else { } 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 */ 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() */ /* 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(); smp_mb();
if ((vdev->guest_features & (1 << VIRTIO_F_NOTIFY_ON_EMPTY)) && 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; return true;
} }
if (!(vdev->guest_features & (1 << VIRTIO_RING_F_EVENT_IDX))) { 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; old = vring->signalled_used;
v = vring->signalled_used_valid; v = vring->signalled_used_valid;
@ -202,9 +205,19 @@ static int get_desc(Vring *vring, VirtQueueElement *elem,
return 0; 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. */ /* This is stolen from linux/drivers/vhost/vhost.c. */
static int get_indirect(Vring *vring, VirtQueueElement *elem, static int get_indirect(VirtIODevice *vdev, Vring *vring,
struct vring_desc *indirect) VirtQueueElement *elem, struct vring_desc *indirect)
{ {
struct vring_desc desc; struct vring_desc desc;
unsigned int i = 0, count, found = 0; unsigned int i = 0, count, found = 0;
@ -244,7 +257,7 @@ static int get_indirect(Vring *vring, VirtQueueElement *elem,
vring->broken = true; vring->broken = true;
return -EFAULT; return -EFAULT;
} }
desc = *desc_ptr; copy_in_vring_desc(vdev, desc_ptr, &desc);
memory_region_unref(mr); memory_region_unref(mr);
/* Ensure descriptor has been loaded before accessing fields */ /* 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. */ /* Check it isn't doing very strange things with descriptor numbers. */
last_avail_idx = vring->last_avail_idx; 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 */ barrier(); /* load indices now and not again later */
if (unlikely((uint16_t)(avail_idx - last_avail_idx) > num)) { 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 /* Grab the next descriptor number they're advertising, and increment
* the index we've seen. */ * 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; elem->index = head;
@ -365,13 +378,13 @@ int vring_pop(VirtIODevice *vdev, Vring *vring,
ret = -EFAULT; ret = -EFAULT;
goto out; goto out;
} }
desc = vring->vr.desc[i]; copy_in_vring_desc(vdev, &vring->vr.desc[i], &desc);
/* Ensure descriptor is loaded before accessing fields */ /* Ensure descriptor is loaded before accessing fields */
barrier(); barrier();
if (desc.flags & VRING_DESC_F_INDIRECT) { if (desc.flags & VRING_DESC_F_INDIRECT) {
ret = get_indirect(vring, elem, &desc); ret = get_indirect(vdev, vring, elem, &desc);
if (ret < 0) { if (ret < 0) {
goto out; goto out;
} }
@ -407,9 +420,9 @@ out:
* *
* Stolen from linux/drivers/vhost/vhost.c. * 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; unsigned int head = elem->index;
uint16_t new; 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 /* The virtqueue contains a ring of used buffers. Get a pointer to the
* next entry in that used ring. */ * next entry in that used ring. */
used = &vring->vr.used->ring[vring->last_used_idx % vring->vr.num]; vring_set_used_ring_id(vdev, vring, vring->last_used_idx % vring->vr.num,
used->id = head; head);
used->len = len; vring_set_used_ring_len(vdev, vring, vring->last_used_idx % vring->vr.num,
len);
/* Make sure buffer is written before we update index. */ /* Make sure buffer is written before we update index. */
smp_wmb(); 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)) { if (unlikely((int16_t)(new - vring->signalled_used) < (uint16_t)1)) {
vring->signalled_used_valid = false; vring->signalled_used_valid = false;
} }

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@ -0,0 +1,75 @@
#ifndef VRING_ACCESSORS_H
#define VRING_ACCESSORS_H
#include "hw/virtio/virtio_ring.h"
#include "hw/virtio/virtio.h"
#include "hw/virtio/virtio-access.h"
static inline uint16_t vring_get_used_idx(VirtIODevice *vdev, Vring *vring)
{
return virtio_tswap16(vdev, vring->vr.used->idx);
}
static inline void vring_set_used_idx(VirtIODevice *vdev, Vring *vring,
uint16_t idx)
{
vring->vr.used->idx = virtio_tswap16(vdev, idx);
}
static inline uint16_t vring_get_avail_idx(VirtIODevice *vdev, Vring *vring)
{
return virtio_tswap16(vdev, vring->vr.avail->idx);
}
static inline uint16_t vring_get_avail_ring(VirtIODevice *vdev, Vring *vring,
int i)
{
return virtio_tswap16(vdev, vring->vr.avail->ring[i]);
}
static inline void vring_set_used_ring_id(VirtIODevice *vdev, Vring *vring,
int i, uint32_t id)
{
vring->vr.used->ring[i].id = virtio_tswap32(vdev, id);
}
static inline void vring_set_used_ring_len(VirtIODevice *vdev, Vring *vring,
int i, uint32_t len)
{
vring->vr.used->ring[i].len = virtio_tswap32(vdev, len);
}
static inline uint16_t vring_get_used_flags(VirtIODevice *vdev, Vring *vring)
{
return virtio_tswap16(vdev, vring->vr.used->flags);
}
static inline uint16_t vring_get_avail_flags(VirtIODevice *vdev, Vring *vring)
{
return virtio_tswap16(vdev, vring->vr.avail->flags);
}
static inline void vring_set_used_flags(VirtIODevice *vdev, Vring *vring,
uint16_t flags)
{
vring->vr.used->flags |= virtio_tswap16(vdev, flags);
}
static inline void vring_clear_used_flags(VirtIODevice *vdev, Vring *vring,
uint16_t flags)
{
vring->vr.used->flags &= virtio_tswap16(vdev, ~flags);
}
static inline unsigned int vring_get_num(Vring *vring)
{
return vring->vr.num;
}
/* Are there more descriptors available? */
static inline bool vring_more_avail(VirtIODevice *vdev, Vring *vring)
{
return vring_get_avail_idx(vdev, vring) != vring->last_avail_idx;
}
#endif

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@ -31,17 +31,6 @@ typedef struct {
bool broken; /* was there a fatal error? */ bool broken; /* was there a fatal error? */
} Vring; } Vring;
static inline unsigned int vring_get_num(Vring *vring)
{
return vring->vr.num;
}
/* Are there more descriptors available? */
static inline bool vring_more_avail(Vring *vring)
{
return vring->vr.avail->idx != vring->last_avail_idx;
}
/* Fail future vring_pop() and vring_push() calls until reset */ /* Fail future vring_pop() and vring_push() calls until reset */
static inline void vring_set_broken(Vring *vring) static inline void vring_set_broken(Vring *vring)
{ {
@ -54,6 +43,7 @@ void vring_disable_notification(VirtIODevice *vdev, Vring *vring);
bool vring_enable_notification(VirtIODevice *vdev, Vring *vring); bool vring_enable_notification(VirtIODevice *vdev, Vring *vring);
bool vring_should_notify(VirtIODevice *vdev, Vring *vring); bool vring_should_notify(VirtIODevice *vdev, Vring *vring);
int vring_pop(VirtIODevice *vdev, Vring *vring, VirtQueueElement *elem); int vring_pop(VirtIODevice *vdev, Vring *vring, VirtQueueElement *elem);
void vring_push(Vring *vring, VirtQueueElement *elem, int len); void vring_push(VirtIODevice *vdev, Vring *vring, VirtQueueElement *elem,
int len);
#endif /* VRING_H */ #endif /* VRING_H */