[PATCH] ppc/EEH: fix crash when adding a device in a slot with DDW

[Thadeu Lima de Souza Cascardo]

On Fri, Dec 28, 2012 at 01:18:24PM +0800, Gavin Shan wrote:
> On Thu, Dec 27, 2012 at 02:34:00PM -0200, Thadeu Lima de Souza Cascardo wrote:
> >The DDW code uses a eeh_dev struct from the pci_dev. However, this is
> >not set until eeh_add_device_late is called.
> >
> >Since pci_bus_add_devices is called before eeh_add_device_late, the PCI
> >devices are added to the bus, making drivers' probe hooks to be called.
> >These will call set_dma_mask, which will call the DDW code, which will
> >require the eeh_dev struct from pci_dev. This would result in a crash,
> >due to a NULL dereference.
> >
> >Calling eeh_add_device_late after pci_bus_add_devices would make the
> >system BUG, because device files shouldn't be added to devices there
> >were not added to the system. So, a new function is needed to add such
> >files only after pci_bus_add_devices have been called.
> >
> 
> Could you please explain for a bit how did you trigger the problem? I'm
> not sure you got it while doing PCI hotplug or just saw the issue during
> system bootup stage :-)
> 

I did a DLPAR remove followed by a DLPAR add, using drmgr -r and drmgr
-a. The reason the issue is not trigerred during bootup is that there is
no driver registered yet. So no driver probe will call dma_set_mask.

> >Cc: stable at vger.kernel.org
> >Signed-off-by: Thadeu Lima de Souza Cascardo <cascardo at linux.vnet.ibm.com>
> >---
> > arch/powerpc/include/asm/eeh.h       |    3 +++
> > arch/powerpc/kernel/pci-common.c     |    7 +++++--
> > arch/powerpc/platforms/pseries/eeh.c |   24 +++++++++++++++++++++++-
> > 3 files changed, 31 insertions(+), 3 deletions(-)
> >
> >diff --git a/arch/powerpc/include/asm/eeh.h b/arch/powerpc/include/asm/eeh.h
> >index b0ef738..71aac19 100644
> >--- a/arch/powerpc/include/asm/eeh.h
> >+++ b/arch/powerpc/include/asm/eeh.h
> >@@ -201,6 +201,7 @@ int eeh_dev_check_failure(struct eeh_dev *edev);
> > void __init eeh_addr_cache_build(void);
> > void eeh_add_device_tree_early(struct device_node *);
> > void eeh_add_device_tree_late(struct pci_bus *);
> >+void eeh_add_device_tree_files(struct pci_bus *);
> 
> Since the function is going to add EEH specific sysfs files, its name would
> be something like "eeh_add_sysfs_files" instead of "eeh_add_device_tree_files" :-)

It's indeed a better name.

> 
> > void eeh_remove_bus_device(struct pci_dev *, int);
> >
> > /**
> >@@ -240,6 +241,8 @@ static inline void eeh_add_device_tree_early(struct device_node *dn) { }
> >
> > static inline void eeh_add_device_tree_late(struct pci_bus *bus) { }
> >
> >+static inline void eeh_add_device_tree_files(struct pci_bus *bus) { }
> >+
> 
> It'd better to rename the function name to "eeh_add_sysfs_files" mentioned
> as above.
> 
> > static inline void eeh_remove_bus_device(struct pci_dev *dev, int purge_pe) { }
> >
> > static inline void eeh_lock(void) { }
> >diff --git a/arch/powerpc/kernel/pci-common.c b/arch/powerpc/kernel/pci-common.c
> >index 7f94f76..7b1f14c 100644
> >--- a/arch/powerpc/kernel/pci-common.c
> >+++ b/arch/powerpc/kernel/pci-common.c
> >@@ -1480,11 +1480,14 @@ void pcibios_finish_adding_to_bus(struct pci_bus *bus)
> > 	pcibios_allocate_bus_resources(bus);
> > 	pcibios_claim_one_bus(bus);
> >
> >+	/* Fixup EEH */
> >+	eeh_add_device_tree_late(bus);
> >+
> > 	/* Add new devices to global lists.  Register in proc, sysfs. */
> > 	pci_bus_add_devices(bus);
> >
> >-	/* Fixup EEH */
> >-	eeh_add_device_tree_late(bus);
> >+	/* Add EEH sysfs files */
> >+	eeh_add_device_tree_files(bus);
> 
> The function name would be "eeh_add_sysfs_files" as above.
> 
> > }
> > EXPORT_SYMBOL_GPL(pcibios_finish_adding_to_bus);
> >
> 
> By the way, arch/powerpc/kernel/of_platform.c::of_pci_phb_probe is also calling
> to eeh_add_device_tree_late() as well. Since you have removed part of the logic
> from original eeh_add_device_tree_late(), which is add EEH specific sysfs files,
> and you put that part of logic to eeh_add_device_tree_files(). So I think you
> also need make the similiar change for of_pci_phb_probe() as well :-)
> 

Good point. I will look into other call sites. However, I don't have
access to other platforms to test the patch.

> >diff --git a/arch/powerpc/platforms/pseries/eeh.c b/arch/powerpc/platforms/pseries/eeh.c
> >index 9a04322..a667a34 100644
> >--- a/arch/powerpc/platforms/pseries/eeh.c
> >+++ b/arch/powerpc/platforms/pseries/eeh.c
> >@@ -788,7 +788,6 @@ static void eeh_add_device_late(struct pci_dev *dev)
> > 	dev->dev.archdata.edev = edev;
> >
> > 	eeh_addr_cache_insert_dev(dev);
> >-	eeh_sysfs_add_device(dev);
> > }
> >
> > /**
> >@@ -815,6 +814,29 @@ void eeh_add_device_tree_late(struct pci_bus *bus)
> > EXPORT_SYMBOL_GPL(eeh_add_device_tree_late);
> >
> > /**
> >+ * eeh_add_device_tree_files - Add EEH sysfs files for the indicated PCI bus
> >+ * @bus: PCI bus
> >+ *
> >+ * This routine must be used to add EEH sysfs files for PCI
> >+ * devices which are attached to the indicated PCI bus. The PCI bus
> >+ * is added after system boot through hotplug or dlpar.
> >+ */
> >+void eeh_add_device_tree_files(struct pci_bus *bus)
> >+{
> >+	struct pci_dev *dev;
> >+
> >+	list_for_each_entry(dev, &bus->devices, bus_list) {
> >+		eeh_sysfs_add_device(dev);
> >+		if (dev->hdr_type == PCI_HEADER_TYPE_BRIDGE) {
> >+			struct pci_bus *subbus = dev->subordinate;
> >+			if (subbus)
> >+				eeh_add_device_tree_files(subbus);
> >+		}
> >+	}
> >+}
> >+EXPORT_SYMBOL_GPL(eeh_add_device_tree_files);
> >+
> 
> The function name mentioned as above.
> 
> >+/**
> >  * eeh_remove_device - Undo EEH setup for the indicated pci device
> >  * @dev: pci device to be removed
> >  * @purge_pe: remove the PE or not
> >
> 
> Thanks,
> Gavin
> 

Regards,
Thadeu Cascardo.