* [Qemu-devel] [PATCH v2 1/1] dataplane: endianness-aware accesses
2015-01-26 16:26 [Qemu-devel] [PATCH v2 0/1] dataplane vs. endianness Cornelia Huck
@ 2015-01-26 16:26 ` Cornelia Huck
2015-01-27 5:15 ` [Qemu-devel] [PATCH v2 0/1] dataplane vs. endianness David Gibson
` (2 subsequent siblings)
3 siblings, 0 replies; 6+ messages in thread
From: Cornelia Huck @ 2015-01-26 16:26 UTC (permalink / raw)
To: Stefan Hajnoczi
Cc: Cornelia Huck, Paolo Bonzini, Fam Zheng, qemu-devel, David Gibson
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>
---
hw/block/dataplane/virtio-blk.c | 4 +-
hw/scsi/virtio-scsi-dataplane.c | 2 +-
hw/virtio/Makefile.objs | 2 +-
hw/virtio/dataplane/Makefile.objs | 2 +-
hw/virtio/dataplane/vring.c | 53 ++++++++++++-------
include/hw/virtio/dataplane/vring-accessors.h | 75 +++++++++++++++++++++++++++
include/hw/virtio/dataplane/vring.h | 14 +----
7 files changed, 117 insertions(+), 35 deletions(-)
create mode 100644 include/hw/virtio/dataplane/vring-accessors.h
diff --git a/hw/block/dataplane/virtio-blk.c b/hw/block/dataplane/virtio-blk.c
index 39c5d71..7ae4e03 100644
--- a/hw/block/dataplane/virtio-blk.c
+++ b/hw/block/dataplane/virtio-blk.c
@@ -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
diff --git a/hw/scsi/virtio-scsi-dataplane.c b/hw/scsi/virtio-scsi-dataplane.c
index 03a1e8c..418d73b 100644
--- a/hw/scsi/virtio-scsi-dataplane.c
+++ b/hw/scsi/virtio-scsi-dataplane.c
@@ -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)) {
diff --git a/hw/virtio/Makefile.objs b/hw/virtio/Makefile.objs
index d21c397..19b224a 100644
--- a/hw/virtio/Makefile.objs
+++ b/hw/virtio/Makefile.objs
@@ -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
diff --git a/hw/virtio/dataplane/Makefile.objs b/hw/virtio/dataplane/Makefile.objs
index 9a8cfc0..753a9ca 100644
--- a/hw/virtio/dataplane/Makefile.objs
+++ b/hw/virtio/dataplane/Makefile.objs
@@ -1 +1 @@
-common-obj-y += vring.o
+obj-y += vring.o
diff --git a/hw/virtio/dataplane/vring.c b/hw/virtio/dataplane/vring.c
index 61f6d83..87d9121 100644
--- a/hw/virtio/dataplane/vring.c
+++ b/hw/virtio/dataplane/vring.c
@@ -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 & 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 & 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;
}
diff --git a/include/hw/virtio/dataplane/vring-accessors.h b/include/hw/virtio/dataplane/vring-accessors.h
new file mode 100644
index 0000000..b508b87
--- /dev/null
+++ b/include/hw/virtio/dataplane/vring-accessors.h
@@ -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
diff --git a/include/hw/virtio/dataplane/vring.h b/include/hw/virtio/dataplane/vring.h
index d3e086a..e42c0fc 100644
--- a/include/hw/virtio/dataplane/vring.h
+++ b/include/hw/virtio/dataplane/vring.h
@@ -31,17 +31,6 @@ typedef struct {
bool broken; /* was there a fatal error? */
} 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 */
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_should_notify(VirtIODevice *vdev, Vring *vring);
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 */
--
2.1.4
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