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    Subject[PATCH 4.4 046/118] cxl: use pcibios_free_controller_deferred() when removing vPHBs
    Date
    4.4-stable review patch.  If anyone has any objections, please let me know.

    ------------------

    From: Andrew Donnellan <andrew.donnellan@au1.ibm.com>

    commit 6f38a8b9a45833495dc878c335c5431cd98a16ed 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: Andrew Donnellan <andrew.donnellan@au1.ibm.com>
    Reviewed-by: Matthew R. Ochs <mrochs@linux.vnet.ibm.com>
    Acked-by: Ian Munsie <imunsie@au1.ibm.com>
    Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

    ---
    drivers/misc/cxl/vphb.c | 10 +++++++++-
    drivers/pci/host-bridge.c | 1 +
    2 files changed, 10 insertions(+), 1 deletion(-)

    --- a/drivers/misc/cxl/vphb.c
    +++ b/drivers/misc/cxl/vphb.c
    @@ -258,6 +258,11 @@ int cxl_pci_vphb_add(struct cxl_afu *afu
    if (phb->bus == NULL)
    return -ENXIO;

    + /* Set release hook on root bus */
    + pci_set_host_bridge_release(to_pci_host_bridge(phb->bus->bridge),
    + pcibios_free_controller_deferred,
    + (void *) phb);
    +
    /* Claim resources. This might need some rework as well depending
    * whether we are doing probe-only or not, like assigning unassigned
    * resources etc...
    @@ -293,7 +298,10 @@ void cxl_pci_vphb_remove(struct cxl_afu
    afu->phb = NULL;

    pci_remove_root_bus(phb->bus);
    - pcibios_free_controller(phb);
    + /*
    + * We don't free phb here - that's handled by
    + * pcibios_free_controller_deferred()
    + */
    }

    struct cxl_afu *cxl_pci_to_afu(struct pci_dev *dev)
    --- a/drivers/pci/host-bridge.c
    +++ b/drivers/pci/host-bridge.c
    @@ -44,6 +44,7 @@ void pci_set_host_bridge_release(struct
    bridge->release_fn = release_fn;
    bridge->release_data = release_data;
    }
    +EXPORT_SYMBOL_GPL(pci_set_host_bridge_release);

    void pcibios_resource_to_bus(struct pci_bus *bus, struct pci_bus_region *region,
    struct resource *res)

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