1. 16 Oct, 2016 2 commits
    • Andrew Donnellan's avatar
      cxl: use pcibios_free_controller_deferred() when removing vPHBs · 3e08bc37
      Andrew Donnellan authored
      commit 6f38a8b9 upstream.
      
      When cxl removes a vPHB, it's possible that the pci_controller may be freed
      before all references to the devices on the vPHB have been released. This
      in turn causes an invalid memory access when the devices are eventually
      released, as pcibios_release_device() attempts to call the phb's
      release_device hook.
      
      In cxl_pci_vphb_remove(), remove the existing call to
      pcibios_free_controller(). Instead, use
      pcibios_free_controller_deferred() to free the pci_controller after all
      devices have been released. Export pci_set_host_bridge_release() so we can
      do this.
      Signed-off-by: default avatarAndrew Donnellan <andrew.donnellan@au1.ibm.com>
      Reviewed-by: default avatarMatthew R. Ochs <mrochs@linux.vnet.ibm.com>
      Acked-by: default avatarIan Munsie <imunsie@au1.ibm.com>
      Signed-off-by: default avatarBenjamin Herrenschmidt <benh@kernel.crashing.org>
      Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
      3e08bc37
    • Mauricio Faria de Oliveira's avatar
      powerpc/pseries: use pci_host_bridge.release_fn() to kfree(phb) · 83573add
      Mauricio Faria de Oliveira authored
      commit 2dd9c11b upstream.
      
      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: default avatarGavin Shan <gwshan@linux.vnet.ibm.com>
      Signed-off-by: default avatarMauricio Faria de Oliveira <mauricfo@linux.vnet.ibm.com>
      Reviewed-by: default avatarGavin Shan <gwshan@linux.vnet.ibm.com>
      Reviewed-by: default avatarAndrew Donnellan <andrew.donnellan@au1.ibm.com>
      Tested-by: Andrew Donnellan <andrew.donnellan@au1.ibm.com> # cxl
      Signed-off-by: default avatarBenjamin Herrenschmidt <benh@kernel.crashing.org>
      Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
      83573add
  2. 07 Oct, 2016 38 commits