forked from Minki/linux
powerpc/pseries: use pci_host_bridge.release_fn() to kfree(phb)
This patch leverages 'struct pci_host_bridge' from the PCI subsystem in order to free the pci_controller only after the last reference to its devices is dropped (avoiding an oops in pcibios_release_device() if the last reference is dropped after pcibios_free_controller()). The patch relies on pci_host_bridge.release_fn() (and .release_data), which is called automatically by the PCI subsystem when the root bus is released (i.e., the last reference is dropped). Those fields are set via pci_set_host_bridge_release() (e.g. in the platform-specific implementation of pcibios_root_bridge_prepare()). It introduces the 'pcibios_free_controller_deferred()' .release_fn() and it expects .release_data to hold a pointer to the pci_controller. The function implictly calls 'pcibios_free_controller()', so an user must *NOT* explicitly call it if using the new _deferred() callback. The functionality is enabled for pseries (although it isn't platform specific, and may be used by cxl). Details on not-so-elegant design choices: - Use 'pci_host_bridge.release_data' field as pointer to associated 'struct pci_controller' so *not* to 'pci_bus_to_host(bridge->bus)' in pcibios_free_controller_deferred(). That's because pci_remove_root_bus() sets 'host_bridge->bus = NULL' (so, if the last reference is released after pci_remove_root_bus() runs, which eventually reaches pcibios_free_controller_deferred(), that would hit a null pointer dereference). The cxl/vphb.c code calls pci_remove_root_bus(), and the cxl folks are interested in this fix. Test-case #1 (hold references) # ls -ld /sys/block/sd* | grep -m1 0021:01:00.0 <...> /sys/block/sdaa -> ../devices/pci0021:01/0021:01:00.0/<...> # ls -ld /sys/block/sd* | grep -m1 0021:01:00.1 <...> /sys/block/sdab -> ../devices/pci0021:01/0021:01:00.1/<...> # cat >/dev/sdaa & pid1=$! # cat >/dev/sdab & pid2=$! # drmgr -w 5 -d 1 -c phb -s 'PHB 33' -r Validating PHB DLPAR capability...yes. [ 594.306719] pci_hp_remove_devices: PCI: Removing devices on bus 0021:01 [ 594.306738] pci_hp_remove_devices: Removing 0021:01:00.0... ... [ 598.236381] pci_hp_remove_devices: Removing 0021:01:00.1... ... [ 611.972077] pci_bus 0021:01: busn_res: [bus 01-ff] is released [ 611.972140] rpadlpar_io: slot PHB 33 removed # kill -9 $pid1 # kill -9 $pid2 [ 632.918088] pcibios_free_controller_deferred: domain 33, dynamic 1 Test-case #2 (don't hold references) # drmgr -w 5 -d 1 -c phb -s 'PHB 33' -r Validating PHB DLPAR capability...yes. [ 916.357363] pci_hp_remove_devices: PCI: Removing devices on bus 0021:01 [ 916.357386] pci_hp_remove_devices: Removing 0021:01:00.0... ... [ 920.566527] pci_hp_remove_devices: Removing 0021:01:00.1... ... [ 933.955873] pci_bus 0021:01: busn_res: [bus 01-ff] is released [ 933.955977] pcibios_free_controller_deferred: domain 33, dynamic 1 [ 933.955999] rpadlpar_io: slot PHB 33 removed Suggested-By: Gavin Shan <gwshan@linux.vnet.ibm.com> Signed-off-by: Mauricio Faria de Oliveira <mauricfo@linux.vnet.ibm.com> Reviewed-by: Gavin Shan <gwshan@linux.vnet.ibm.com> Reviewed-by: Andrew Donnellan <andrew.donnellan@au1.ibm.com> Tested-by: Andrew Donnellan <andrew.donnellan@au1.ibm.com> # cxl Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
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@ -301,6 +301,7 @@ extern void pci_process_bridge_OF_ranges(struct pci_controller *hose,
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/* Allocate & free a PCI host bridge structure */
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extern struct pci_controller *pcibios_alloc_controller(struct device_node *dev);
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extern void pcibios_free_controller(struct pci_controller *phb);
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extern void pcibios_free_controller_deferred(struct pci_host_bridge *bridge);
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#ifdef CONFIG_PCI
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extern int pcibios_vaddr_is_ioport(void __iomem *address);
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@ -153,6 +153,42 @@ void pcibios_free_controller(struct pci_controller *phb)
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}
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EXPORT_SYMBOL_GPL(pcibios_free_controller);
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/*
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* This function is used to call pcibios_free_controller()
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* in a deferred manner: a callback from the PCI subsystem.
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*
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* _*DO NOT*_ call pcibios_free_controller() explicitly if
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* this is used (or it may access an invalid *phb pointer).
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*
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* The callback occurs when all references to the root bus
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* are dropped (e.g., child buses/devices and their users).
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*
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* It's called as .release_fn() of 'struct pci_host_bridge'
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* which is associated with the 'struct pci_controller.bus'
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* (root bus) - it expects .release_data to hold a pointer
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* to 'struct pci_controller'.
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*
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* In order to use it, register .release_fn()/release_data
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* like this:
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*
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* pci_set_host_bridge_release(bridge,
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* pcibios_free_controller_deferred
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* (void *) phb);
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*
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* e.g. in the pcibios_root_bridge_prepare() callback from
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* pci_create_root_bus().
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*/
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void pcibios_free_controller_deferred(struct pci_host_bridge *bridge)
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{
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struct pci_controller *phb = (struct pci_controller *)
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bridge->release_data;
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pr_debug("domain %d, dynamic %d\n", phb->global_number, phb->is_dynamic);
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pcibios_free_controller(phb);
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}
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EXPORT_SYMBOL_GPL(pcibios_free_controller_deferred);
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/*
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* The function is used to return the minimal alignment
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* for memory or I/O windows of the associated P2P bridge.
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@ -119,6 +119,10 @@ int pseries_root_bridge_prepare(struct pci_host_bridge *bridge)
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bus = bridge->bus;
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/* Rely on the pcibios_free_controller_deferred() callback. */
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pci_set_host_bridge_release(bridge, pcibios_free_controller_deferred,
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(void *) pci_bus_to_host(bus));
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dn = pcibios_get_phb_of_node(bus);
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if (!dn)
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return 0;
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@ -106,8 +106,11 @@ int remove_phb_dynamic(struct pci_controller *phb)
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release_resource(res);
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}
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/* Free pci_controller data structure */
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pcibios_free_controller(phb);
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/*
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* The pci_controller data structure is freed by
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* the pcibios_free_controller_deferred() callback;
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* see pseries_root_bridge_prepare().
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*/
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return 0;
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}
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