| Message ID | 20240219112422.54657-1-beanhuo@iokpp.de |
|---|---|
| State | New |
| Headers | show |
| Series | [v3] PCI: Increase maximum PCIe physical function number to 7 for non-ARI devices | expand |
On 24/02/19 12:24PM, Bean Huo wrote: > From: Bean Huo <beanhuo@micron.com> > > As per PCIe r6.2, sec 6.13 titled "Alternative Routing-ID Interpretation > (ARI)", up to 8 [fn # 0..7] Physical Functions(PFs) are allowed in an > non-ARI capable device. Previously, our implementation erroneously limited > the maximum number of PFs to 7 for endpoints without ARI support. > > This patch corrects the maximum PF count to adhere to the PCIe specification > by allowing up to 8 PFs on non-ARI capable devices. This change ensures better > compliance with the standard and improves compatibility with devices relying > on this specification. The function "next_fn()" seems to provide the next valid function. Therefore, if the current function is 0 (fn = 0), then the next valid function will be 1 which is returned by next_fn(). It extends similarly until the case where current function is 6 (fn = 6) which shall return the next valid function as 7. So all 8 PFs are still treated as valid and there doesn't seem to be any limitation. Only in the case where the EP doesn't support ARI (there is no function 8 (fn = 8)), the call to next_fn() with the fn parameter set to 7, will return -ENODEV which seems to be the expected behavior. Regards, Siddharth. > > Fixes: c3df83e01a96 ("PCI: Clean up pci_scan_slot()") > Cc: stable@vger.kernel.org > Signed-off-by: Bean Huo <beanhuo@micron.com> > --- > Changelog: > v2--v3: > 1. Update commit messag > v1--v2: > 1. Add Fixes tag > 2. Modify commit message > --- > drivers/pci/probe.c | 3 ++- > 1 file changed, 2 insertions(+), 1 deletion(-) > > diff --git a/drivers/pci/probe.c b/drivers/pci/probe.c > index ed6b7f48736a..8c3d0f63bc13 100644 > --- a/drivers/pci/probe.c > +++ b/drivers/pci/probe.c > @@ -2630,7 +2630,8 @@ static int next_fn(struct pci_bus *bus, struct pci_dev *dev, int fn) > if (pci_ari_enabled(bus)) > return next_ari_fn(bus, dev, fn); > > - if (fn >= 7) > + /* If EP does not support ARI, the maximum number of functions should be 7 */ > + if (fn > 7) > return -ENODEV; > /* only multifunction devices may have more functions */ > if (dev && !dev->multifunction) > -- > 2.34.1 > >
On Mon, 2024-02-19 at 17:30 +0530, Siddharth Vadapalli wrote: > The function "next_fn()" seems to provide the next valid function. > Therefore, if the current function is 0 (fn = 0), then the next valid > function will be 1 which is returned by next_fn(). It extends > similarly > until the case where current function is 6 (fn = 6) which shall > return > the next valid function as 7. So all 8 PFs are still treated as valid > and there doesn't seem to be any limitation. Only in the case where > the > EP doesn't support ARI (there is no function 8 (fn = 8)), the call to > next_fn() with the fn parameter set to 7, will return -ENODEV which > seems to be the expected behavior. > > Regards, > Siddharth. yes, you are right, the fn 7 has no next_fn, hence should return - ENODEV. ignore this patch! kind regards, Bean
diff --git a/drivers/pci/probe.c b/drivers/pci/probe.c index ed6b7f48736a..8c3d0f63bc13 100644 --- a/drivers/pci/probe.c +++ b/drivers/pci/probe.c @@ -2630,7 +2630,8 @@ static int next_fn(struct pci_bus *bus, struct pci_dev *dev, int fn) if (pci_ari_enabled(bus)) return next_ari_fn(bus, dev, fn); - if (fn >= 7) + /* If EP does not support ARI, the maximum number of functions should be 7 */ + if (fn > 7) return -ENODEV; /* only multifunction devices may have more functions */ if (dev && !dev->multifunction)