On Mon, Apr 08, 2013 at 09:09:54PM -0700, Nicholas A. Bellinger wrote:
> Ping.
>
> Any ideas on this one..? It seems like this bug would be effecting
> non vhost-scsi-pci code as well..
Nicholas, where is the latest v3 code. Can you push it to your tree.
> --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@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@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@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@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.
Ah, I did not see this before. If we disable SeaBIOS and only use guest
kernel to access tcm_vhost disk, do you see this.
> > 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..? */
Pretty strange.
> > + if (GET_LOWFLAT(vr->num) != MAX_QUEUE_NUM) {
> > + SET_LOWFLAT(vr->num, MAX_QUEUE_NUM);
> > + }
> > return more;
> > }
> >
> > --
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>
>
--
Asias
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