On Mon, 2024-11-04 at 10:14 +0100, Philipp Stanner wrote:
> On Thu, 2024-10-31 at 14:42 +0100, Takashi Iwai wrote:
> > pcim_intx() tries to restore the INTx bit at removal via devres,
> > but
> > there is a chance that it restores a wrong value.
> > Because the value to be restored is blindly assumed to be the
> > negative
> > of the enable argument, when a driver calls pcim_intx()
> > unnecessarily
> > for the already enabled state, it'll restore to the disabled state
> > in
> > turn. That is, the function assumes the case like:
> >
> > // INTx == 1
> > pcim_intx(pdev, 0); // old INTx value assumed to be 1 -> correct
> >
> > but it might be like the following, too:
> >
> > // INTx == 0
> > pcim_intx(pdev, 0); // old INTx value assumed to be 1 -> wrong
> >
> > Also, when a driver calls pcim_intx() multiple times with different
> > enable argument values, the last one will win no matter what value
> > it
> > is. This can lead to inconsistency, e.g.
> >
> > // INTx == 1
> > pcim_intx(pdev, 0); // OK
> > ...
> > pcim_intx(pdev, 1); // now old INTx wrongly assumed to be 0
> >
> > This patch addresses those inconsistencies by saving the original
> > INTx state at the first pcim_intx() call. For that,
> > get_or_create_intx_devres() is folded into pcim_intx() caller side;
> > it allows us to simply check the already allocated devres and
> > record
> > the original INTx along with the devres_alloc() call.
> >
> > Fixes: 25216afc9db5 ("PCI: Add managed pcim_intx()")
> > Cc: stable@xxxxxxxxxxxxxxx # 6.11+
> > Link: https://lore.kernel.org/87v7xk2ps5.wl-tiwai@xxxxxxx
> > Signed-off-by: Takashi Iwai <tiwai@xxxxxxx>
>
> Reviewed-by: Philipp Stanner <pstanner@xxxxxxxxxx>
Hello,
it seems we forgot about this patch.
Regards,
P.
>
> Nice!
>
> > ---
> > v1->v2: refactoring, fold get_or_create_intx_devres() into the
> > caller
> > instead of retrieving the original INTx there.
> > Also add comments and improve the patch description.
> >
> > drivers/pci/devres.c | 34 +++++++++++++++++++---------------
> > 1 file changed, 19 insertions(+), 15 deletions(-)
> >
> > diff --git a/drivers/pci/devres.c b/drivers/pci/devres.c
> > index b133967faef8..c93d4d4499a0 100644
> > --- a/drivers/pci/devres.c
> > +++ b/drivers/pci/devres.c
> > @@ -438,19 +438,12 @@ static void pcim_intx_restore(struct device
> > *dev, void *data)
> > __pcim_intx(pdev, res->orig_intx);
> > }
> >
> > -static struct pcim_intx_devres *get_or_create_intx_devres(struct
> > device *dev)
> > +static void save_orig_intx(struct pci_dev *pdev, struct
> > pcim_intx_devres *res)
> > {
> > - struct pcim_intx_devres *res;
> > + u16 pci_command;
> >
> > - res = devres_find(dev, pcim_intx_restore, NULL, NULL);
> > - if (res)
> > - return res;
> > -
> > - res = devres_alloc(pcim_intx_restore, sizeof(*res),
> > GFP_KERNEL);
> > - if (res)
> > - devres_add(dev, res);
> > -
> > - return res;
> > + pci_read_config_word(pdev, PCI_COMMAND, &pci_command);
> > + res->orig_intx = !(pci_command &
> > PCI_COMMAND_INTX_DISABLE);
> > }
> >
> > /**
> > @@ -466,12 +459,23 @@ static struct pcim_intx_devres
> > *get_or_create_intx_devres(struct device *dev)
> > int pcim_intx(struct pci_dev *pdev, int enable)
> > {
> > struct pcim_intx_devres *res;
> > + struct device *dev = &pdev->dev;
> >
> > - res = get_or_create_intx_devres(&pdev->dev);
> > - if (!res)
> > - return -ENOMEM;
> > + /*
> > + * pcim_intx() must only restore the INTx value that
> > existed
> > before the
> > + * driver was loaded, i.e., before it called pcim_intx()
> > for
> > the
> > + * first time.
> > + */
> > + res = devres_find(dev, pcim_intx_restore, NULL, NULL);
> > + if (!res) {
> > + res = devres_alloc(pcim_intx_restore,
> > sizeof(*res),
> > GFP_KERNEL);
> > + if (!res)
> > + return -ENOMEM;
> > +
> > + save_orig_intx(pdev, res);
> > + devres_add(dev, res);
> > + }
> >
> > - res->orig_intx = !enable;
> > __pcim_intx(pdev, enable);
> >
> > return 0;
>
