Re: [Qemu-devel] [PATCH V3 WIP 3/3] disable vhost_verify_ring_mappings check

[Nicholas A. Bellinger]

On Wed, 2013-03-20 at 11:51 +0200, Michael S. Tsirkin wrote:
> On Tue, Mar 19, 2013 at 06:57:08PM -0700, Nicholas A. Bellinger wrote:
> > On Tue, 2013-03-19 at 09:40 +0100, Stefan Hajnoczi wrote:
> > > On Tue, Mar 19, 2013 at 08:34:45AM +0800, Asias He wrote:
> > > > ---
> > > >  hw/vhost.c | 2 ++
> > > >  1 file changed, 2 insertions(+)
> > > > 
> > > > diff --git a/hw/vhost.c b/hw/vhost.c
> > > > index 4d6aee3..0c52ec4 100644
> > > > --- a/hw/vhost.c
> > > > +++ b/hw/vhost.c
> > > > @@ -421,10 +421,12 @@ static void vhost_set_memory(MemoryListener 
> > > > *listener,
> > > >          return;
> > > >      }
> > > >  
> > > > +#if 0
> > > >      if (dev->started) {
> > > >          r = vhost_verify_ring_mappings(dev, start_addr, size);
> > > >          assert(r >= 0);
> > > >      }
> > > > +#endif
> > > 
> > > Please add a comment to explain why.
> > > 
> > 
> > Btw, the output that Asias added in the failure case at the behest of
> > MST is here:
> > 
> > http://www.spinics.net/lists/target-devel/msg04077.html
> 
> Yes I suspected we could get l > ring_size, but this is
> not the case here.
> 

Hi MST & Co,

A quick update here..

So this issue appears to be related to performing the
vhost_verify_ring_mappings() call after vhost_dev_unassign_memory() has
been invoked with vhost_set_memory(..., add=false).

AFAICT from the logs below, things appear to work as expected when
vhost_verify_ring_mappings() is called only for the
vhost_set_memory(..., add=true) case.

Calling vhost_verify_ring_mappings() when dev->started == true +
vhost_set_memory(..., add=false) appears to be a bug caused by fallout
from:

commit 24f4fe345c1b80bab1ee18573914123d8028a9e6
Author: Michael S. Tsirkin <address@hidden>
Date:   Tue Dec 25 17:41:07 2012 +0200

    vhost: set started flag while start is in progress

I'm including the following patch in the forth-coming vhost-scsi series.
Please let me know if you have any concerns.

diff --git a/hw/vhost.c b/hw/vhost.c
index 4d6aee3..687a689 100644
--- a/hw/vhost.c
+++ b/hw/vhost.c
@@ -421,7 +421,7 @@ static void vhost_set_memory(MemoryListener *listener,
         return;
     }
 
-    if (dev->started) {
+    if (dev->started && add) {
         r = vhost_verify_ring_mappings(dev, start_addr, size);
         assert(r >= 0);
     }

Thanks!

--nab

vhost_set_memory: section: 0x7f2249986b60 section->size: 2146697216 add: 0
Before vhost_verify_ring_mappings: start_addr: c0000 size: 2146697216
Checking vq: 0 ring_phys: 0 ring_size: 1028 >>>>>>>>>>>>>>>>>>.
Got ranges_overlap for vq: 0 ring_phys: 0 ring_size: 1028
Checking vq: 1 ring_phys: 0 ring_size: 1028 >>>>>>>>>>>>>>>>>>.
Got ranges_overlap for vq: 1 ring_phys: 0 ring_size: 1028
Checking vq: 2 ring_phys: ee000 ring_size: 5124 >>>>>>>>>>>>>>>>>>.
Calling l: 5124 for start_addr: c0000 for vq 2
Unable to map ring buffer for ring 2
l: 4096 ring_size: 5124
vhost_set_memory: section: 0x7f2249986aa0 section->size: 32768 add: 1
Before vhost_verify_ring_mappings: start_addr: c0000 size: 32768
Checking vq: 0 ring_phys: 0 ring_size: 1028 >>>>>>>>>>>>>>>>>>.
Got ranges_overlap for vq: 0 ring_phys: 0 ring_size: 1028
Checking vq: 1 ring_phys: 0 ring_size: 1028 >>>>>>>>>>>>>>>>>>.
Got ranges_overlap for vq: 1 ring_phys: 0 ring_size: 1028
Checking vq: 2 ring_phys: ee000 ring_size: 5124 >>>>>>>>>>>>>>>>>>.
Got ranges_overlap for vq: 2 ring_phys: ee000 ring_size: 5124
vhost_set_memory: section: 0x7f2249986aa0 section->size: 2146664448 add: 1
Before vhost_verify_ring_mappings: start_addr: c8000 size: 2146664448
Checking vq: 0 ring_phys: 0 ring_size: 1028 >>>>>>>>>>>>>>>>>>.
Got ranges_overlap for vq: 0 ring_phys: 0 ring_size: 1028
Checking vq: 1 ring_phys: 0 ring_size: 1028 >>>>>>>>>>>>>>>>>>.
Got ranges_overlap for vq: 1 ring_phys: 0 ring_size: 1028
Checking vq: 2 ring_phys: ee000 ring_size: 5124 >>>>>>>>>>>>>>>>>>.
Calling l: 5124 for start_addr: c8000 for vq 2
vhost_set_memory: section: 0x7f2249986b60 section->size: 32768 add: 0
Before vhost_verify_ring_mappings: start_addr: c0000 size: 32768
Checking vq: 0 ring_phys: 0 ring_size: 1028 >>>>>>>>>>>>>>>>>>.
Got ranges_overlap for vq: 0 ring_phys: 0 ring_size: 1028
Checking vq: 1 ring_phys: 0 ring_size: 1028 >>>>>>>>>>>>>>>>>>.
Got ranges_overlap for vq: 1 ring_phys: 0 ring_size: 1028
Checking vq: 2 ring_phys: ee000 ring_size: 5124 >>>>>>>>>>>>>>>>>>.
Got ranges_overlap for vq: 2 ring_phys: ee000 ring_size: 5124
vhost_set_memory: section: 0x7f2249986b60 section->size: 2146664448 add: 0
Before vhost_verify_ring_mappings: start_addr: c8000 size: 2146664448
Checking vq: 0 ring_phys: 0 ring_size: 1028 >>>>>>>>>>>>>>>>>>.
Got ranges_overlap for vq: 0 ring_phys: 0 ring_size: 1028
Checking vq: 1 ring_phys: 0 ring_size: 1028 >>>>>>>>>>>>>>>>>>.
Got ranges_overlap for vq: 1 ring_phys: 0 ring_size: 1028
Checking vq: 2 ring_phys: ee000 ring_size: 5124 >>>>>>>>>>>>>>>>>>.
Calling l: 5124 for start_addr: c8000 for vq 2
Unable to map ring buffer for ring 2
l: 0 ring_size: 5124
vhost_set_memory: section: 0x7f2249986aa0 section->size: 36864 add: 1
Before vhost_verify_ring_mappings: start_addr: c0000 size: 36864
Checking vq: 0 ring_phys: 0 ring_size: 1028 >>>>>>>>>>>>>>>>>>.
Got ranges_overlap for vq: 0 ring_phys: 0 ring_size: 1028
Checking vq: 1 ring_phys: 0 ring_size: 1028 >>>>>>>>>>>>>>>>>>.
Got ranges_overlap for vq: 1 ring_phys: 0 ring_size: 1028
Checking vq: 2 ring_phys: ee000 ring_size: 5124 >>>>>>>>>>>>>>>>>>.
Got ranges_overlap for vq: 2 ring_phys: ee000 ring_size: 5124
vhost_set_memory: section: 0x7f2249986aa0 section->size: 2146660352 add: 1
Before vhost_verify_ring_mappings: start_addr: c9000 size: 2146660352
Checking vq: 0 ring_phys: 0 ring_size: 1028 >>>>>>>>>>>>>>>>>>.
Got ranges_overlap for vq: 0 ring_phys: 0 ring_size: 1028
Checking vq: 1 ring_phys: 0 ring_size: 1028 >>>>>>>>>>>>>>>>>>.
Got ranges_overlap for vq: 1 ring_phys: 0 ring_size: 1028
Checking vq: 2 ring_phys: ee000 ring_size: 5124 >>>>>>>>>>>>>>>>>>.
Calling l: 5124 for start_addr: c9000 for vq 2
vhost_set_memory: section: 0x7f2249986b60 section->size: 2146660352 add: 0
Before vhost_verify_ring_mappings: start_addr: c9000 size: 2146660352
Checking vq: 0 ring_phys: 0 ring_size: 1028 >>>>>>>>>>>>>>>>>>.
Got ranges_overlap for vq: 0 ring_phys: 0 ring_size: 1028
Checking vq: 1 ring_phys: 0 ring_size: 1028 >>>>>>>>>>>>>>>>>>.
Got ranges_overlap for vq: 1 ring_phys: 0 ring_size: 1028
Checking vq: 2 ring_phys: ee000 ring_size: 5124 >>>>>>>>>>>>>>>>>>.
Calling l: 5124 for start_addr: c9000 for vq 2
Unable to map ring buffer for ring 2
l: 0 ring_size: 5124
vhost_set_memory: section: 0x7f2249986aa0 section->size: 159744 add: 1
Before vhost_verify_ring_mappings: start_addr: c9000 size: 159744
Checking vq: 0 ring_phys: 0 ring_size: 1028 >>>>>>>>>>>>>>>>>>.
Got ranges_overlap for vq: 0 ring_phys: 0 ring_size: 1028
Checking vq: 1 ring_phys: 0 ring_size: 1028 >>>>>>>>>>>>>>>>>>.
Got ranges_overlap for vq: 1 ring_phys: 0 ring_size: 1028
Checking vq: 2 ring_phys: ee000 ring_size: 5124 >>>>>>>>>>>>>>>>>>.
Calling l: 5124 for start_addr: c9000 for vq 2
vhost_set_memory: section: 0x7f2249986aa0 section->size: 65536 add: 1
Before vhost_verify_ring_mappings: start_addr: f0000 size: 65536
Checking vq: 0 ring_phys: 0 ring_size: 1028 >>>>>>>>>>>>>>>>>>.
Got ranges_overlap for vq: 0 ring_phys: 0 ring_size: 1028
Checking vq: 1 ring_phys: 0 ring_size: 1028 >>>>>>>>>>>>>>>>>>.
Got ranges_overlap for vq: 1 ring_phys: 0 ring_size: 1028
Checking vq: 2 ring_phys: ee000 ring_size: 5124 >>>>>>>>>>>>>>>>>>.
Got ranges_overlap for vq: 2 ring_phys: ee000 ring_size: 5124
vhost_set_memory: section: 0x7f2249986aa0 section->size: 2146435072 add: 1
Before vhost_verify_ring_mappings: start_addr: 100000 size: 2146435072
Checking vq: 0 ring_phys: 0 ring_size: 1028 >>>>>>>>>>>>>>>>>>.
Got ranges_overlap for vq: 0 ring_phys: 0 ring_size: 1028
Checking vq: 1 ring_phys: 0 ring_size: 1028 >>>>>>>>>>>>>>>>>>.
Got ranges_overlap for vq: 1 ring_phys: 0 ring_size: 1028
Checking vq: 2 ring_phys: ee000 ring_size: 5124 >>>>>>>>>>>>>>>>>>.
Got ranges_overlap for vq: 2 ring_phys: ee000 ring_size: 5124