Re: [PATCH 09/11] PCI: add matching checks for driver_override binding

[Max Gurtovoy]

On 6/16/2021 3:34 AM, Jason Gunthorpe wrote:
> On Tue, Jun 15, 2021 at 06:22:45PM -0600, Alex Williamson wrote:
> > On Tue, 15 Jun 2021 20:32:57 -0300
> > Jason Gunthorpe <jgg@xxxxxxxxxx> wrote:
> >
> > > On Tue, Jun 15, 2021 at 05:22:42PM -0600, Alex Williamson wrote:
> > >
> > > > > > b) alone is a functional, runtime difference.
> > > > > I would state b) differently:
> > > > >
> > > > > b) Ignore the driver-override-only match entries in the ID table.
> > > > No, pci_match_device() returns NULL if a match is found that is marked
> > > > driver-override-only and a driver_override is not specified.  That's
> > > > the same as no match at all.  We don't then go on to search past that
> > > > match in the table, we fail to bind the driver.  That's effectively an
> > > > anti-match when there's no driver_override on the device.
> > > anti-match isn't the intention. The deployment will have match tables
> > > where all entires are either flags=0 or are driver-override-only.
> > I'd expect pci-pf-stub to have one of each, an any-id with
> > override-only flag and the one device ID currently in the table with
> > no flag.
> Oh Hum. Actually I think this shows the anti-match behavior is
> actually a bug.. :(
>
> For something like pci_pf_stub_whitelist, if we add a
> driver_override-only using the PCI any id then it effectively disables
> new_id completely because the match search will alway find the
> driver_override match first and stop searching. There is no chance to
> see things new_id adds.

Actually the dynamic table is the first table the driver search. So 
new_id works exactly the same AFAIU.

But you're right for static mixed table (I assumed that this will never 
happen I guess).

If we put the any_id_override id before the non_override AMAZON device 
entry in the pci-pf-stub we'll fail with the matching to the AMAZON device.

What about the bellow untested addition (also remove condition c):

diff --git a/drivers/pci/pci-driver.c b/drivers/pci/pci-driver.c
index 296de7bc9dc9..2d46f6cd96f7 100644
--- a/drivers/pci/pci-driver.c
+++ b/drivers/pci/pci-driver.c
@@ -136,7 +136,7 @@ static const struct pci_device_id 
*pci_match_device(struct pci_driver *drv,
                                                    struct pci_dev *dev)
 {
        struct pci_dynid *dynid;
-       const struct pci_device_id *found_id = NULL;
+       const struct pci_device_id *found_id = NULL, *ids;

        /* When driver_override is set, only bind to the matching driver */
        if (dev->driver_override && strcmp(dev->driver_override, 
drv->name))
@@ -155,8 +155,8 @@ static const struct pci_device_id 
*pci_match_device(struct pci_driver *drv,
        if (found_id)
                return found_id;

-       found_id = pci_match_id(drv->id_table, dev);
-       if (found_id) {
+       ids = drv->id_table;
+       while ((found_id = pci_match_id(ids, dev))) {
                /*
                 * if we found id in the static table, we must fulfill the
                 * matching flags (i.e. if PCI_ID_F_DRIVER_OVERRIDE flag is
@@ -164,17 +164,19 @@ static const struct pci_device_id 
*pci_match_device(struct pci_driver *drv,
                 */
                bool is_driver_override =
                        (found_id->flags & PCI_ID_F_DRIVER_OVERRIDE) != 0;
-               if ((is_driver_override && !dev->driver_override) ||
-                   (dev->driver_override && !is_driver_override))
-                       return NULL;
-       } else if (dev->driver_override) {
-               /*
-                * if we didn't find suitable id in the static table,
-                * driver_override will still , send a dummy id
-                */
-               found_id = &pci_device_id_any;
+               if (is_driver_override && !dev->driver_override)
+                       ids = found_id++; /* continue searching */
+               else
+                       break;
        }

+       /*
+        * if no static match, driver_override will always match, send a 
dummy
+        * id.
+        */
+       if (!found_id && dev->driver_override)
+               found_id = &pci_device_id_any;
+
        return found_id;
 }

diff --git a/drivers/pci/pci-pf-stub.c b/drivers/pci/pci-pf-stub.c
index 45855a5e9fca..49544ba9a7af 100644
--- a/drivers/pci/pci-pf-stub.c
+++ b/drivers/pci/pci-pf-stub.c
@@ -19,6 +19,7 @@
  */
 static const struct pci_device_id pci_pf_stub_whitelist[] = {
        { PCI_VDEVICE(AMAZON, 0x0053) },
+       { PCI_DEVICE_FLAGS(PCI_ANY_ID, PCI_ANY_ID, 
PCI_ID_F_STUB_DRIVER_OVERRIDE) }, /* match all by default (override) */
        /* required last entry */
        { 0 }
 };


> We have to fix this patch so flags isn't an anti-match to make it work
> without user regression.
>
> Jason