[1/3] bus/pci: update device devargs on each rescan

  Bus rescan is done e.g. during the device hotplug,
where devargs are re-allocated. By not updating the
rte_device->devargs pointer we potentially make it
a dangling one, as previous devargs could have been
(or will be soon) freed.

Fixes: 55e411b301c3 ("bus/pci: fix resource mapping override")
Cc: qi.z.zhang@intel.com

Signed-off-by: Darek Stojaczyk <dariusz.stojaczyk@intel.com>
---
 drivers/bus/pci/linux/pci.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
  

Hi Darek,

On Mon, Nov 05, 2018 at 08:04:45AM +0100, Darek Stojaczyk wrote:
> Bus rescan is done e.g. during the device hotplug,
> where devargs are re-allocated. By not updating the
> rte_device->devargs pointer we potentially make it
> a dangling one, as previous devargs could have been
> (or will be soon) freed.
> 
> Fixes: 55e411b301c3 ("bus/pci: fix resource mapping override")
> Cc: qi.z.zhang@intel.com
> 
> Signed-off-by: Darek Stojaczyk <dariusz.stojaczyk@intel.com>
> ---
>  drivers/bus/pci/linux/pci.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/bus/pci/linux/pci.c b/drivers/bus/pci/linux/pci.c
> index f87533c5c..f3172960e 100644
> --- a/drivers/bus/pci/linux/pci.c
> +++ b/drivers/bus/pci/linux/pci.c
> @@ -349,10 +349,10 @@ pci_scan_one(const char *dirname, const struct rte_pci_addr *addr)
>  			if (ret < 0) {
>  				rte_pci_insert_device(dev2, dev);
>  			} else { /* already registered */
> +				pci_name_set(dev2);

This is rather unfortunate to call pci_name_set()
to trigger the mapping devargs <-> devices.

pci_devargs_lookup could be made non-static instead,
if that's sufficient. Given that the PCI id matches because the device
is a duplicate (already registered), then the name itself probably does
not need to be updated.

>  				if (!rte_dev_is_probed(&dev2->device)) {
>  					dev2->kdrv = dev->kdrv;
>  					dev2->max_vfs = dev->max_vfs;
> -					pci_name_set(dev2);
>  					memmove(dev2->mem_resource,
>  						dev->mem_resource,
>  						sizeof(dev->mem_resource));
> -- 
> 2.17.1
>
  

Hi Gaetan,

> -----Original Message-----
> From: Gaëtan Rivet [mailto:gaetan.rivet@6wind.com]
> Subject: Re: [dpdk-dev] [PATCH 1/3] bus/pci: update device devargs on each
> rescan
> 
> Hi Darek,
> 
> On Mon, Nov 05, 2018 at 08:04:45AM +0100, Darek Stojaczyk wrote:
> > Bus rescan is done e.g. during the device hotplug,
> > where devargs are re-allocated. By not updating the
> > rte_device->devargs pointer we potentially make it
> > a dangling one, as previous devargs could have been
> > (or will be soon) freed.
> >
> > Fixes: 55e411b301c3 ("bus/pci: fix resource mapping override")
> > Cc: qi.z.zhang@intel.com
> >
> > Signed-off-by: Darek Stojaczyk <dariusz.stojaczyk@intel.com>
> > ---
> >  drivers/bus/pci/linux/pci.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/drivers/bus/pci/linux/pci.c b/drivers/bus/pci/linux/pci.c
> > index f87533c5c..f3172960e 100644
> > --- a/drivers/bus/pci/linux/pci.c
> > +++ b/drivers/bus/pci/linux/pci.c
> > @@ -349,10 +349,10 @@ pci_scan_one(const char *dirname, const struct
> rte_pci_addr *addr)
> >  			if (ret < 0) {
> >  				rte_pci_insert_device(dev2, dev);
> >  			} else { /* already registered */
> > +				pci_name_set(dev2);
> 
> This is rather unfortunate to call pci_name_set()
> to trigger the mapping devargs <-> devices.
> 
> pci_devargs_lookup could be made non-static instead,
> if that's sufficient. 

This is unfortunately trigerred by the generic eal device hotplug path which looks as follows:

da = calloc(sizeof rte_devargs);
[...]
rte_devargs_insert(da); # frees the previous devargs that rte_device still references
da->bus->scan(); # this should update the dangling devargs/name pointer in rte_device

Instead of making pci_devargs_lookup public, we would have to introduce a new bus callback for updating devargs of only a single device and that would be a really, realy ugly overkill. Thomas already mentioned in the subsequent patch within this series that we might want to re-think the devargs design in the next release.

> Given that the PCI id matches because the device
> is a duplicate (already registered), then the name itself probably does
> not need to be updated.

The issue here was that old devargs/name could have been freed.
The new name is the same as the old one, it's just in a different buffer.

I know calling pci_name_set() on each device during scan is not perfect, but IMO it's enforced by the current rte_devargs design. Besides, this used to be the original behavior before 55e411b301c3 ("bus/pci: fix resource mapping override").

Thanks,
D.

> 
> >  <snip>
> 
> --
> Gaëtan Rivet
> 6WIND
  

On Mon, Nov 05, 2018 at 02:52:00PM +0000, Stojaczyk, Dariusz wrote:
> Hi Gaetan,
> 
> > -----Original Message-----
> > From: Gaëtan Rivet [mailto:gaetan.rivet@6wind.com]
> > Subject: Re: [dpdk-dev] [PATCH 1/3] bus/pci: update device devargs on each
> > rescan
> > 
> > Hi Darek,
> > 
> > On Mon, Nov 05, 2018 at 08:04:45AM +0100, Darek Stojaczyk wrote:
> > > Bus rescan is done e.g. during the device hotplug,
> > > where devargs are re-allocated. By not updating the
> > > rte_device->devargs pointer we potentially make it
> > > a dangling one, as previous devargs could have been
> > > (or will be soon) freed.
> > >
> > > Fixes: 55e411b301c3 ("bus/pci: fix resource mapping override")
> > > Cc: qi.z.zhang@intel.com
> > >
> > > Signed-off-by: Darek Stojaczyk <dariusz.stojaczyk@intel.com>
> > > ---
> > >  drivers/bus/pci/linux/pci.c | 2 +-
> > >  1 file changed, 1 insertion(+), 1 deletion(-)
> > >
> > > diff --git a/drivers/bus/pci/linux/pci.c b/drivers/bus/pci/linux/pci.c
> > > index f87533c5c..f3172960e 100644
> > > --- a/drivers/bus/pci/linux/pci.c
> > > +++ b/drivers/bus/pci/linux/pci.c
> > > @@ -349,10 +349,10 @@ pci_scan_one(const char *dirname, const struct
> > rte_pci_addr *addr)
> > >  			if (ret < 0) {
> > >  				rte_pci_insert_device(dev2, dev);
> > >  			} else { /* already registered */
> > > +				pci_name_set(dev2);
> > 
> > This is rather unfortunate to call pci_name_set()
> > to trigger the mapping devargs <-> devices.
> > 
> > pci_devargs_lookup could be made non-static instead,
> > if that's sufficient. 
> 
> This is unfortunately trigerred by the generic eal device hotplug path which looks as follows:
> 
> da = calloc(sizeof rte_devargs);
> [...]
> rte_devargs_insert(da); # frees the previous devargs that rte_device still references
> da->bus->scan(); # this should update the dangling devargs/name pointer in rte_device
> 
> Instead of making pci_devargs_lookup public, we would have to introduce a new bus callback for updating devargs of only a single device and that would be a really, realy ugly overkill. Thomas already mentioned in the subsequent patch within this series that we might want to re-think the devargs design in the next release.
> 

No, of course, I'm not saying to make pci_devargs_lookup public, only
private to the PCI bus, and within the bus, non-static. This way,
instead of calling pci_name_set(), you call instead only
pci_devargs_lookup().

> > Given that the PCI id matches because the device
> > is a duplicate (already registered), then the name itself probably does
> > not need to be updated.
> 
> The issue here was that old devargs/name could have been freed.
> The new name is the same as the old one, it's just in a different buffer.
> 
> I know calling pci_name_set() on each device during scan is not perfect, but IMO it's enforced by the current rte_devargs design. Besides, this used to be the original behavior before 55e411b301c3 ("bus/pci: fix resource mapping override").
> 
> Thanks,
> D.
> 
> > 
> > >  <snip>
> > 
> > --
> > Gaëtan Rivet
> > 6WIND