Nicholas A. Bellinger
2013-Apr-05 02:59 UTC
Bug in SeaBIOS virtio-ring handling bug with vhost-scsi-pci
Hi Paolo & Co,
So I've been running into another bug with SeaBIOS w/ virtio-scsi +
vhost-scsi-pci code..
During the last weeks debugging on the QEMU vhost memory re-mapping bug,
my seabios builds have been using a smaller target ID (16) for scanning
than the default hard coded value of 256 in init_virtio_scsi().
After bumping this value back to 256 recently, a bogus out_num value
from vhost_get_vq_desc() start appearing on the tcm_vhost side:
[17348.044031] Invalid buffer layout out: 0 in: 2
After adding more debug output to SeaBIOS, the vring->num value appears
to be reset from the expected MAX_QUEUE_NUM=128, then incremented each
time after vring_more_used() is called to poll for completion..
init virtio-scsi
found virtio-scsi at 0:4
vring_init Setting vr->num: 128
Calling virtio_scsi_scan_target for target: 0
Searching bootorder for: /pci at i0cf8/*@4/*@0/*@0,0
virtio_scsi_cmd, using vring_add_buf for out_num: 1 in_num: 2
virtio_scsi_cmd, using vring_add_buf vr: 0x000ed404 vr->num: 128
vring_add_buf, vr: 0x000ed404 vr->num: 128
vring_add_buf, head: 0, index: 0
vring_add_buf, setting desc[prev=2].flags
vring_add_buf, setting free_head: 3
vring_add_buf, setting q->vdata[head=0]
vring_add_buf, setting q->ring[av=0]
virtio_scsi_cmd, after vring_add_buf vr: 0x000ed404 vr->num: 128
virtio_scsi_cmd, after vring_kick vr: 0x000ed404 vr->num: 128
virtio_scsi_cmd, after vring_more_used #4 vr: 0x000ed404 vr->num: 1
^^^^^^^^^^^^^^^^^^^^^^^^^
Reset from 128 to 1 immediate after first vring_more_used()..?
vring_get_buf last_used_idx: 0 vr: 0x000ed404 vr->num: 1
vring_get_buf checking &used->ring[0]
vring_get_buf, using new last_unsed: 0
>>>>>>>>>>>>>>>>>>
vring_get_buf using id: 0 from elem->id: 0x000ed004
vring_detach: vq->free_head: 3
vring_detach: Setting new vq->free_head: 0
virtio_scsi_cmd, after vring_get_buf #5 vr: 0x000ed404 vr->num: 1
Calling virtio_scsi_scan_target for target: 1
Searching bootorder for: /pci at i0cf8/*@4/*@0/*@1,0
virtio_scsi_cmd, using vring_add_buf for out_num: 1 in_num: 2
virtio_scsi_cmd, using vring_add_buf vr: 0x000ed404 vr->num: 1
vring_add_buf, vr: 0x000ed404 vr->num: 1
vring_add_buf, head: 0, index: 0
vring_add_buf, setting desc[prev=2].flags
vring_add_buf, setting free_head: 3
vring_add_buf, setting q->vdata[head=0]
vring_add_buf, setting q->ring[av=0]
virtio_scsi_cmd, after vring_add_buf vr: 0x000ed404 vr->num: 1
virtio_scsi_cmd, after vring_kick vr: 0x000ed404 vr->num: 1
virtio_scsi_cmd, after vring_more_used #4 vr: 0x000ed404 vr->num: 2
^^^^^^^^^^^^^^^^^^^^^^^^^
Incremented from 1 to 2 after second vring_more_used()..?
vring_get_buf last_used_idx: 1 vr: 0x000ed404 vr->num: 2
vring_get_buf checking &used->ring[1]
vring_get_buf, using new last_unsed: 1
>>>>>>>>>>>>>>>>>>
vring_get_buf using id: 0 from elem->id: 0x000ed00c
vring_detach: vq->free_head: 3
vring_detach: Setting new vq->free_head: 0
virtio_scsi_cmd, after vring_get_buf #5 vr: 0x000ed404 vr->num: 2
virtio-scsi vendor='LIO-ORG' product='RAMDISK-MCP'
rev='4.0' type=0 removable=0
virtio_scsi_cmd, using vring_add_buf for out_num: 1 in_num: 1
virtio_scsi_cmd, using vring_add_buf vr: 0x000ed404 vr->num: 2
vring_add_buf, vr: 0x000ed404 vr->num: 2
vring_add_buf, head: 0, index: 0
vring_add_buf, setting desc[prev=1].flags
vring_add_buf, setting free_head: 2
vring_add_buf, setting q->vdata[head=0]
vring_add_buf, setting q->ring[av=0]
virtio_scsi_cmd, after vring_add_buf vr: 0x000ed404 vr->num: 2
virtio_scsi_cmd, after vring_kick vr: 0x000ed404 vr->num: 2
virtio_scsi_cmd, after vring_more_used #4 vr: 0x000ed404 vr->num: 3
^^^^^^^^^^^^^^^^^^^^^^^^^
Incremented from 2 to 3, and so on..
and this keeps happening until vr->num begins to exceed
MAX_QUEUE_NUM around scanning of target ID 127:
virtio_scsi_cmd, after vring_add_buf vr: 0x000ed404 vr->num: 128
virtio_scsi_cmd, after vring_kick vr: 0x000ed404 vr->num: 128
virtio_scsi_cmd, after vring_more_used #4 vr: 0x000ed404 vr->num: 129
vring_get_buf last_used_idx: 128 vr: 0x000ed404 vr->num: 129
vring_get_buf checking &used->ring[128]
vring_get_buf, using new last_unsed: 128
>>>>>>>>>>>>>>>>>>
vring_get_buf using id: 129 from elem->id: 0x000ed404
vring_detach: vq->free_head: 3
vring_detach: Setting new vq->free_head: 129
virtio_scsi_cmd, after vring_get_buf #5 vr: 0x000ed404 vr->num: 129
Calling virtio_scsi_scan_target for target: 127
Searching bootorder for: /pci at i0cf8/*@4/*@0/*@127,0
virtio_scsi_cmd, using vring_add_buf for out_num: 1 in_num: 2
virtio_scsi_cmd, using vring_add_buf vr: 0x000ed404 vr->num: 129
vring_add_buf, vr: 0x000ed404 vr->num: 129
vring_add_buf, head: 129, index: 0
vring_add_buf, setting desc[prev=4].flags
vring_add_buf, setting free_head: 5
vring_add_buf, setting q->vdata[head=0]
vring_add_buf, setting q->ring[av=129]
virtio_scsi_cmd, after vring_add_buf vr: 0x000ed404 vr->num: 129
virtio_scsi_cmd, after vring_kick vr: 0x000ed404 vr->num: 129
virtio_scsi_cmd, after vring_more_used #4 vr: 0x000ed404 vr->num: 130
vring_get_buf last_used_idx: 129 vr: 0x000ed404 vr->num: 130
vring_get_buf checking &used->ring[129]
vring_get_buf, using new last_unsed: 129
>>>>>>>>>>>>>>>>>>
vring_get_buf using id: 968704 from elem->id: 0x000ed40c
vring_detach: vq->free_head: 5
vring_detach: Setting new vq->free_head: 968704
virtio_scsi_cmd, after vring_get_buf #5 vr: 0x000ed404 vr->num: 130
Calling virtio_scsi_scan_target for target: 128
Searching bootorder for: /pci at i0cf8/*@4/*@0/*@128,0
virtio_scsi_cmd, using vring_add_buf for out_num: 1 in_num: 2
virtio_scsi_cmd, using vring_add_buf vr: 0x000ed404 vr->num: 130
vring_add_buf, vr: 0x000ed404 vr->num: 130
vring_add_buf, head: 51200, index: 0
vring_add_buf, setting desc[prev=1].flags
vring_add_buf, setting free_head: 2
vring_add_buf, setting q->vdata[head=0]
vring_add_buf, setting q->ring[av=51200]
until '[17348.044031] Invalid buffer layout out: 0 in: 2' appears on the
vhost.
So it's clear this definitely is not supposed to be happening, but I've
not yet been able to ascertain why it's suddenly being triggered now..?
I don't recall Asias running into a similar issue during his earlier
testing, but this bug is happening after every I/O in SeaBIOS with the
most recent vhost-scsi-pci code.
I'm using the following to work-around this issue for the moment, and
would like some input from virtio / SeaBIOS folks..
WDYT..?
--nab
diff --git a/src/virtio-ring.c b/src/virtio-ring.c
index bddb090..e046141 100644
--- a/src/virtio-ring.c
+++ b/src/virtio-ring.c
@@ -35,10 +35,16 @@
int vring_more_used(struct vring_virtqueue *vq)
{
+ struct vring *vr = &vq->vring;
struct vring_used *used = GET_LOWFLAT(vq->vring.used);
int more = GET_LOWFLAT(vq->last_used_idx) != GET_LOWFLAT(used->idx);
/* Make sure ring reads are done after idx read above. */
smp_rmb();
+
+ /* Huh..? vr->num is somehow changing from below us..? */
+ if (GET_LOWFLAT(vr->num) != MAX_QUEUE_NUM) {
+ SET_LOWFLAT(vr->num, MAX_QUEUE_NUM);
+ }
return more;
}
Nicholas A. Bellinger
2013-Apr-09 04:09 UTC
Bug in SeaBIOS virtio-ring handling bug with vhost-scsi-pci
Ping. Any ideas on this one..? It seems like this bug would be effecting non vhost-scsi-pci code as well.. --nab On Thu, 2013-04-04 at 19:59 -0700, Nicholas A. Bellinger wrote:> Hi Paolo & Co, > > So I've been running into another bug with SeaBIOS w/ virtio-scsi + > vhost-scsi-pci code.. > > During the last weeks debugging on the QEMU vhost memory re-mapping bug, > my seabios builds have been using a smaller target ID (16) for scanning > than the default hard coded value of 256 in init_virtio_scsi(). > > After bumping this value back to 256 recently, a bogus out_num value > from vhost_get_vq_desc() start appearing on the tcm_vhost side: > > [17348.044031] Invalid buffer layout out: 0 in: 2 > > After adding more debug output to SeaBIOS, the vring->num value appears > to be reset from the expected MAX_QUEUE_NUM=128, then incremented each > time after vring_more_used() is called to poll for completion.. > > init virtio-scsi > found virtio-scsi at 0:4 > vring_init Setting vr->num: 128 > Calling virtio_scsi_scan_target for target: 0 > Searching bootorder for: /pci at i0cf8/*@4/*@0/*@0,0 > virtio_scsi_cmd, using vring_add_buf for out_num: 1 in_num: 2 > virtio_scsi_cmd, using vring_add_buf vr: 0x000ed404 vr->num: 128 > vring_add_buf, vr: 0x000ed404 vr->num: 128 > vring_add_buf, head: 0, index: 0 > vring_add_buf, setting desc[prev=2].flags > vring_add_buf, setting free_head: 3 > vring_add_buf, setting q->vdata[head=0] > vring_add_buf, setting q->ring[av=0] > virtio_scsi_cmd, after vring_add_buf vr: 0x000ed404 vr->num: 128 > virtio_scsi_cmd, after vring_kick vr: 0x000ed404 vr->num: 128 > virtio_scsi_cmd, after vring_more_used #4 vr: 0x000ed404 vr->num: 1 > ^^^^^^^^^^^^^^^^^^^^^^^^^ > > Reset from 128 to 1 immediate after first vring_more_used()..? > > vring_get_buf last_used_idx: 0 vr: 0x000ed404 vr->num: 1 > vring_get_buf checking &used->ring[0] > vring_get_buf, using new last_unsed: 0 >>>>>>>>>>>>>>>>>> > vring_get_buf using id: 0 from elem->id: 0x000ed004 > vring_detach: vq->free_head: 3 > vring_detach: Setting new vq->free_head: 0 > virtio_scsi_cmd, after vring_get_buf #5 vr: 0x000ed404 vr->num: 1 > Calling virtio_scsi_scan_target for target: 1 > Searching bootorder for: /pci at i0cf8/*@4/*@0/*@1,0 > virtio_scsi_cmd, using vring_add_buf for out_num: 1 in_num: 2 > virtio_scsi_cmd, using vring_add_buf vr: 0x000ed404 vr->num: 1 > vring_add_buf, vr: 0x000ed404 vr->num: 1 > vring_add_buf, head: 0, index: 0 > vring_add_buf, setting desc[prev=2].flags > vring_add_buf, setting free_head: 3 > vring_add_buf, setting q->vdata[head=0] > vring_add_buf, setting q->ring[av=0] > virtio_scsi_cmd, after vring_add_buf vr: 0x000ed404 vr->num: 1 > virtio_scsi_cmd, after vring_kick vr: 0x000ed404 vr->num: 1 > virtio_scsi_cmd, after vring_more_used #4 vr: 0x000ed404 vr->num: 2 > ^^^^^^^^^^^^^^^^^^^^^^^^^ > > Incremented from 1 to 2 after second vring_more_used()..? > > vring_get_buf last_used_idx: 1 vr: 0x000ed404 vr->num: 2 > vring_get_buf checking &used->ring[1] > vring_get_buf, using new last_unsed: 1 >>>>>>>>>>>>>>>>>> > vring_get_buf using id: 0 from elem->id: 0x000ed00c > vring_detach: vq->free_head: 3 > vring_detach: Setting new vq->free_head: 0 > virtio_scsi_cmd, after vring_get_buf #5 vr: 0x000ed404 vr->num: 2 > virtio-scsi vendor='LIO-ORG' product='RAMDISK-MCP' rev='4.0' type=0 removable=0 > virtio_scsi_cmd, using vring_add_buf for out_num: 1 in_num: 1 > virtio_scsi_cmd, using vring_add_buf vr: 0x000ed404 vr->num: 2 > vring_add_buf, vr: 0x000ed404 vr->num: 2 > vring_add_buf, head: 0, index: 0 > vring_add_buf, setting desc[prev=1].flags > vring_add_buf, setting free_head: 2 > vring_add_buf, setting q->vdata[head=0] > vring_add_buf, setting q->ring[av=0] > virtio_scsi_cmd, after vring_add_buf vr: 0x000ed404 vr->num: 2 > virtio_scsi_cmd, after vring_kick vr: 0x000ed404 vr->num: 2 > virtio_scsi_cmd, after vring_more_used #4 vr: 0x000ed404 vr->num: 3 > ^^^^^^^^^^^^^^^^^^^^^^^^^ > > Incremented from 2 to 3, and so on.. > > and this keeps happening until vr->num begins to exceed > MAX_QUEUE_NUM around scanning of target ID 127: > > virtio_scsi_cmd, after vring_add_buf vr: 0x000ed404 vr->num: 128 > virtio_scsi_cmd, after vring_kick vr: 0x000ed404 vr->num: 128 > virtio_scsi_cmd, after vring_more_used #4 vr: 0x000ed404 vr->num: 129 > vring_get_buf last_used_idx: 128 vr: 0x000ed404 vr->num: 129 > vring_get_buf checking &used->ring[128] > vring_get_buf, using new last_unsed: 128 >>>>>>>>>>>>>>>>>> > vring_get_buf using id: 129 from elem->id: 0x000ed404 > vring_detach: vq->free_head: 3 > vring_detach: Setting new vq->free_head: 129 > virtio_scsi_cmd, after vring_get_buf #5 vr: 0x000ed404 vr->num: 129 > Calling virtio_scsi_scan_target for target: 127 > Searching bootorder for: /pci at i0cf8/*@4/*@0/*@127,0 > virtio_scsi_cmd, using vring_add_buf for out_num: 1 in_num: 2 > virtio_scsi_cmd, using vring_add_buf vr: 0x000ed404 vr->num: 129 > vring_add_buf, vr: 0x000ed404 vr->num: 129 > vring_add_buf, head: 129, index: 0 > vring_add_buf, setting desc[prev=4].flags > vring_add_buf, setting free_head: 5 > vring_add_buf, setting q->vdata[head=0] > vring_add_buf, setting q->ring[av=129] > virtio_scsi_cmd, after vring_add_buf vr: 0x000ed404 vr->num: 129 > virtio_scsi_cmd, after vring_kick vr: 0x000ed404 vr->num: 129 > virtio_scsi_cmd, after vring_more_used #4 vr: 0x000ed404 vr->num: 130 > vring_get_buf last_used_idx: 129 vr: 0x000ed404 vr->num: 130 > vring_get_buf checking &used->ring[129] > vring_get_buf, using new last_unsed: 129 >>>>>>>>>>>>>>>>>> > vring_get_buf using id: 968704 from elem->id: 0x000ed40c > vring_detach: vq->free_head: 5 > vring_detach: Setting new vq->free_head: 968704 > virtio_scsi_cmd, after vring_get_buf #5 vr: 0x000ed404 vr->num: 130 > Calling virtio_scsi_scan_target for target: 128 > Searching bootorder for: /pci at i0cf8/*@4/*@0/*@128,0 > virtio_scsi_cmd, using vring_add_buf for out_num: 1 in_num: 2 > virtio_scsi_cmd, using vring_add_buf vr: 0x000ed404 vr->num: 130 > vring_add_buf, vr: 0x000ed404 vr->num: 130 > vring_add_buf, head: 51200, index: 0 > vring_add_buf, setting desc[prev=1].flags > vring_add_buf, setting free_head: 2 > vring_add_buf, setting q->vdata[head=0] > vring_add_buf, setting q->ring[av=51200] > > until '[17348.044031] Invalid buffer layout out: 0 in: 2' appears on the > vhost. > > So it's clear this definitely is not supposed to be happening, but I've > not yet been able to ascertain why it's suddenly being triggered now..? > I don't recall Asias running into a similar issue during his earlier > testing, but this bug is happening after every I/O in SeaBIOS with the > most recent vhost-scsi-pci code. > > I'm using the following to work-around this issue for the moment, and > would like some input from virtio / SeaBIOS folks.. > > WDYT..? > > --nab > > diff --git a/src/virtio-ring.c b/src/virtio-ring.c > index bddb090..e046141 100644 > --- a/src/virtio-ring.c > +++ b/src/virtio-ring.c > @@ -35,10 +35,16 @@ > > int vring_more_used(struct vring_virtqueue *vq) > { > + struct vring *vr = &vq->vring; > struct vring_used *used = GET_LOWFLAT(vq->vring.used); > int more = GET_LOWFLAT(vq->last_used_idx) != GET_LOWFLAT(used->idx); > /* Make sure ring reads are done after idx read above. */ > smp_rmb(); > + > + /* Huh..? vr->num is somehow changing from below us..? */ > + if (GET_LOWFLAT(vr->num) != MAX_QUEUE_NUM) { > + SET_LOWFLAT(vr->num, MAX_QUEUE_NUM); > + } > return more; > } > > -- > To unsubscribe from this list: send the line "unsubscribe target-devel" in > the body of a message to majordomo at vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html