| Message ID | 20150820212109.GB14810@google.com |
|---|---|
| State | Not Applicable |
| Delegated to: | David Miller |
| Headers | show |
From: Bjorn Helgaas <bhelgaas@google.com> Date: Thu, 20 Aug 2015 16:21:09 -0500 > On Thu, Aug 20, 2015 at 01:58:32PM -0700, David Miller wrote: >> From: Bjorn Helgaas <bhelgaas@google.com> >> Date: Thu, 20 Aug 2015 15:21:35 -0500 >> >> > On Thu, Aug 20, 2015 at 11:40:42AM -0700, David Miller wrote: >> >> From: Bjorn Helgaas <bhelgaas@google.com> >> >> Date: Thu, 20 Aug 2015 11:23:43 -0700 >> >> >> >> > On Thu, Aug 20, 2015 at 10:47 AM, David Miller <davem@davemloft.net> wrote: >> >> >> From: Bjorn Helgaas <bhelgaas@google.com> >> >> >> Date: Thu, 20 Aug 2015 00:48:00 -0500 >> >> >> >> >> >>> [+cc Dave, Eric, Ben, sparclinux] >> >> >> >> >> >> I think the comment is terrible. >> >> > >> >> > I'll update the comment if you suggest some text. Do you object >> >> > mainly to the mention of the specific systems? >> >> >> >> "PCI root complex can not be assumed to be instantiated in the PCI bus >> >> hierarchy." >> > >> > AIUI, the root complex itself (as distinct from root ports) doesn't >> > normally appear in the PCI hierarchy, so I reworded it as follows. I hope >> > this helps address your objection, but if not, I can try again. >> >> This is fine, but it was the comment we were talking about adjusting not >> the commit message :-) > > Oh, sorry! I totally misread that. Here's another try. This also looks fine: Acked-by: David S. Miller <davem@davemloft.net> -- To unsubscribe from this list: send the line "unsubscribe sparclinux" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
Hi Bjorn, David, thanks for your effort to improve the patch commit. Thanks! Yijing. > commit 27ff9f3e0ab34a75a3420bffd3eb5316de2e4d92 > Author: Yijing Wang <wangyijing@huawei.com> > Date: Mon Aug 17 18:47:58 2015 +0800 > > PCI: Tolerate hierarchies with no Root Port > > We should not assume any particular hardware topology. Commit d0751b98dfa3 > ("PCI: Add dev->has_secondary_link to track downstream PCIe links") relied > on the assumption that every PCIe hierarchy is rooted at a Root Port. But > we can't rely on any assumption about what hardware we will find; we just > have to deal with the world as it is. > > On some platforms, PCIe devices (endpoints, switch upstream ports, etc.) > appear directly on the root bus, and there is no Root Port in the PCI bus > hierarchy. For example, Meelis observed these top-level devices on a > Sparc V245: > > 0000:02:00.0 PCI bridge to [bus 03-0d] Switch Upstream Port > 0001:02:00.0 PCI bridge to [bus 03] PCIe to PCI/PCI-X Bridge > > These devices *look* like they have links going upstream, but there really > are no upstream devices. > > In set_pcie_port_type(), we used the parent device to figure out which side > of a switch port has a link, so if the parent device did not exist, we > dereferenced a NULL parent pointer. > > Check whether the parent device exists before dereferencing it. > > Meelis observed this oops on Sparc V245 and T2000. Ben Herrenschmidt says > this is also possible on IBM PowerVM guests on PowerPC. > > [bhelgaas: changelog, comment] > Link: http://lkml.kernel.org/r/alpine.LRH.2.20.1508122118210.18637@math.ut.ee > Reported-by: Meelis Roos <mroos@linux.ee> > Tested-by: Meelis Roos <mroos@linux.ee> > Signed-off-by: Yijing Wang <wangyijing@huawei.com> > Signed-off-by: Bjorn Helgaas <bhelgaas@google.com> > > diff --git a/drivers/pci/probe.c b/drivers/pci/probe.c > index cefd636..b978bbf 100644 > --- a/drivers/pci/probe.c > +++ b/drivers/pci/probe.c > @@ -997,7 +997,12 @@ void set_pcie_port_type(struct pci_dev *pdev) > else if (type == PCI_EXP_TYPE_UPSTREAM || > type == PCI_EXP_TYPE_DOWNSTREAM) { > parent = pci_upstream_bridge(pdev); > - if (!parent->has_secondary_link) > + > + /* > + * Usually there's a parent device (Root Port or Switch > + * Downstream Port), but we can't assume one exists. > + */ > + if (parent && !parent->has_secondary_link) > pdev->has_secondary_link = 1; > } > } > > . > -- To unsubscribe from this list: send the line "unsubscribe sparclinux" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
diff --git a/drivers/pci/probe.c b/drivers/pci/probe.c index cefd636..b978bbf 100644 --- a/drivers/pci/probe.c +++ b/drivers/pci/probe.c @@ -997,7 +997,12 @@ void set_pcie_port_type(struct pci_dev *pdev) else if (type == PCI_EXP_TYPE_UPSTREAM || type == PCI_EXP_TYPE_DOWNSTREAM) { parent = pci_upstream_bridge(pdev); - if (!parent->has_secondary_link) + + /* + * Usually there's a parent device (Root Port or Switch + * Downstream Port), but we can't assume one exists. + */ + if (parent && !parent->has_secondary_link) pdev->has_secondary_link = 1; } }