From 2dd9c11b9d4dfbd6c070eab7b81197f65e82f1a0 Mon Sep 17 00:00:00 2001 From: Mauricio Faria de Oliveira Date: Thu, 11 Aug 2016 17:25:40 -0300 Subject: [PATCH] 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 Signed-off-by: Mauricio Faria de Oliveira Reviewed-by: Gavin Shan Reviewed-by: Andrew Donnellan Tested-by: Andrew Donnellan # cxl Signed-off-by: Benjamin Herrenschmidt --- arch/powerpc/include/asm/pci-bridge.h | 1 + arch/powerpc/kernel/pci-common.c | 36 ++++++++++++++++++++++++++++++ arch/powerpc/platforms/pseries/pci.c | 4 ++++ arch/powerpc/platforms/pseries/pci_dlpar.c | 7 ++++-- 4 files changed, 46 insertions(+), 2 deletions(-) diff --git a/arch/powerpc/include/asm/pci-bridge.h b/arch/powerpc/include/asm/pci-bridge.h index b5e88e4a171a..c0309c59bed8 100644 --- a/arch/powerpc/include/asm/pci-bridge.h +++ b/arch/powerpc/include/asm/pci-bridge.h @@ -301,6 +301,7 @@ extern void pci_process_bridge_OF_ranges(struct pci_controller *hose, /* Allocate & free a PCI host bridge structure */ extern struct pci_controller *pcibios_alloc_controller(struct device_node *dev); extern void pcibios_free_controller(struct pci_controller *phb); +extern void pcibios_free_controller_deferred(struct pci_host_bridge *bridge); #ifdef CONFIG_PCI extern int pcibios_vaddr_is_ioport(void __iomem *address); diff --git a/arch/powerpc/kernel/pci-common.c b/arch/powerpc/kernel/pci-common.c index 7fdf324d5b51..e58908066b0e 100644 --- a/arch/powerpc/kernel/pci-common.c +++ b/arch/powerpc/kernel/pci-common.c @@ -154,6 +154,42 @@ void pcibios_free_controller(struct pci_controller *phb) EXPORT_SYMBOL_GPL(pcibios_free_controller); /* + * This function is used to call pcibios_free_controller() + * in a deferred manner: a callback from the PCI subsystem. + * + * _*DO NOT*_ call pcibios_free_controller() explicitly if + * this is used (or it may access an invalid *phb pointer). + * + * The callback occurs when all references to the root bus + * are dropped (e.g., child buses/devices and their users). + * + * It's called as .release_fn() of 'struct pci_host_bridge' + * which is associated with the 'struct pci_controller.bus' + * (root bus) - it expects .release_data to hold a pointer + * to 'struct pci_controller'. + * + * In order to use it, register .release_fn()/release_data + * like this: + * + * pci_set_host_bridge_release(bridge, + * pcibios_free_controller_deferred + * (void *) phb); + * + * e.g. in the pcibios_root_bridge_prepare() callback from + * pci_create_root_bus(). + */ +void pcibios_free_controller_deferred(struct pci_host_bridge *bridge) +{ + struct pci_controller *phb = (struct pci_controller *) + bridge->release_data; + + pr_debug("domain %d, dynamic %d\n", phb->global_number, phb->is_dynamic); + + pcibios_free_controller(phb); +} +EXPORT_SYMBOL_GPL(pcibios_free_controller_deferred); + +/* * The function is used to return the minimal alignment * for memory or I/O windows of the associated P2P bridge. * By default, 4KiB alignment for I/O windows and 1MiB for diff --git a/arch/powerpc/platforms/pseries/pci.c b/arch/powerpc/platforms/pseries/pci.c index fe16a50700de..09eba5a9929a 100644 --- a/arch/powerpc/platforms/pseries/pci.c +++ b/arch/powerpc/platforms/pseries/pci.c @@ -119,6 +119,10 @@ int pseries_root_bridge_prepare(struct pci_host_bridge *bridge) bus = bridge->bus; + /* Rely on the pcibios_free_controller_deferred() callback. */ + pci_set_host_bridge_release(bridge, pcibios_free_controller_deferred, + (void *) pci_bus_to_host(bus)); + dn = pcibios_get_phb_of_node(bus); if (!dn) return 0; diff --git a/arch/powerpc/platforms/pseries/pci_dlpar.c b/arch/powerpc/platforms/pseries/pci_dlpar.c index 906dbaa97fe2..547fd13e4f8e 100644 --- a/arch/powerpc/platforms/pseries/pci_dlpar.c +++ b/arch/powerpc/platforms/pseries/pci_dlpar.c @@ -106,8 +106,11 @@ int remove_phb_dynamic(struct pci_controller *phb) release_resource(res); } - /* Free pci_controller data structure */ - pcibios_free_controller(phb); + /* + * The pci_controller data structure is freed by + * the pcibios_free_controller_deferred() callback; + * see pseries_root_bridge_prepare(). + */ return 0; } -- 2.11.0