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

[Michael S. Tsirkin]

On Wed, Mar 27, 2013 at 02:31:27PM -0700, Nicholas A. Bellinger wrote:
> 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

Sorry NAK,
I think this will shut down too much stuff:
the main reason to check is when we delete a region.

> 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

I still do not understand how this happened.  Somehow a memory region
was deleted after vhost_dev_start but before vhost_virtqueue_start was
called?
Can you set a breakpoint there and see please?