Patchwork Bug in SeaBIOS virtio-ring handling bug with vhost-scsi-pci

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Submitter Nicholas A. Bellinger
Date April 5, 2013, 2:59 a.m.
Message ID <1365130792.8507.30.camel@haakon2.linux-iscsi.org>
Download mbox | patch
Permalink /patch/234027/
State New
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Nicholas A. Bellinger - April 5, 2013, 2:59 a.m.
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.

I'm using the following to work-around this issue for the moment, and
would like some input from virtio / SeaBIOS folks..

WDYT..?

--nab
Nicholas A. Bellinger - April 9, 2013, 4:09 a.m.
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@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.
> 
> 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;
>  }
> 
> --
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Asias He - April 9, 2013, 4:24 a.m.
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;
> >  }
> > 
> > --
> > To unsubscribe from this list: send the line "unsubscribe target-devel" in
> > the body of a message to majordomo@vger.kernel.org
> > More majordomo info at  http://vger.kernel.org/majordomo-info.html
> 
>
Nicholas A. Bellinger - April 9, 2013, 4:33 a.m.
On Tue, 2013-04-09 at 12:24 +0800, Asias He wrote:
> 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. 
> 

Sure.  Just pushed to:

http://git.kernel.org/cgit/virt/kvm/nab/qemu-kvm.git/log/?h=vhost-scsi-for-1.4

and should be appearing momentarily.

--nab

> > --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;
> > >  }
> > > 
> > > --
> > > To unsubscribe from this list: send the line "unsubscribe target-devel" in
> > > the body of a message to majordomo@vger.kernel.org
> > > More majordomo info at  http://vger.kernel.org/majordomo-info.html
> > 
> > 
>
Paolo Bonzini - April 9, 2013, 7:16 a.m.
Il 09/04/2013 06:33, Nicholas A. Bellinger ha scritto:
>> > Nicholas, where is the latest v3 code. Can you push it to your tree. 
>> > 
> Sure.  Just pushed to:
> 
> http://git.kernel.org/cgit/virt/kvm/nab/qemu-kvm.git/log/?h=vhost-scsi-for-1.4
> 
> and should be appearing momentarily.

I'm going to test my rebase today.

Paolo

Patch

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;
 }