On Mon, Nov 05, 2018 at 02:52:00PM +0000, Stojaczyk, Dariusz wrote:
> Hi Gaetan,
>
> > -----Original Message-----
> > From: Gaëtan Rivet [mailto:gaetan.ri...@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.zh...@intel.com
> > >
> > > Signed-off-by: Darek Stojaczyk <dariusz.stojac...@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
--
Gaëtan Rivet
6WIND
