| Message ID | 20241031134300.10296-1-tiwai@suse.de (mailing list archive) |
|---|---|
| State | New |
| Delegated to: | Bjorn Helgaas |
| Headers | show |
| Series | [v2] PCI: Restore the original INTX_DISABLE bit by pcim_intx() | expand |
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@vger.kernel.org # 6.11+ > Link: https://lore.kernel.org/87v7xk2ps5.wl-tiwai@suse.de > Signed-off-by: Takashi Iwai <tiwai@suse.de> Reviewed-by: Philipp Stanner <pstanner@redhat.com> 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;
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;
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@vger.kernel.org # 6.11+ Link: https://lore.kernel.org/87v7xk2ps5.wl-tiwai@suse.de Signed-off-by: Takashi Iwai <tiwai@suse.de> --- 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(-)