Re: [PATCH v3] powerpc/pseries: use pci_host_bridge.release_fn() to kfree(phb)

On Thu, Aug 11, 2016 at 03:01:44PM +1000, Andrew Donnellan wrote:

On 11/08/16 07:45, Mauricio Faria de Oliveira wrote:

In cxl, we currently call:

pci_remove_root_bus(phb->bus);
pcibios_free_controller(phb);

which appears to break with this patch after I wire up
pci_set_host_bridge_release() in cxl, as phb can be freed before we call
pcibios_free_controller().

pcibios_free_controller() isn't called when bridge's release_fn() is wired
up by pci_set_host_bridge_release(). So you can keep the code as what
you have and no changes needed.

It seems slightly wrong for me to write:

struct pci_bus *bus = phb->bus;
pcibios_free_controller(phb);
pci_remove_root_bus(bus);

Yeah, the sequence needs to be reversed. The released PHB instance could
possibly be accessed inside pci_remove_root_bus(). 

Thanks,
Gavin

quoted

Test-case:

 # 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.
 [  479.547020] pci_hp_remove_devices: PCI: Removing devices on bus 0021:01
 [  479.547049] pci_hp_remove_devices:    Removing 0021:01:00.0...
 ...
 [  483.536303] pci_hp_remove_devices:    Removing 0021:01:00.1...
 ...
 [  497.072130] pci_bus 0021:01: busn_res: [bus 01-ff] is released
 [  497.072209] rpadlpar_io: slot PHB 33 removed

 # kill -9 $pid1
 # kill -9 $pid2
 [  506.604458] pcibios_host_bridge_release: domain 33, dynamic 1

Suggested-By: Gavin Shan <redacted>
Signed-off-by: Mauricio Faria de Oliveira <redacted>

Missing a '---' here :)

quoted

Changelog:
- v3: different approach: struct pci_host_bridge.release_fn()
- v2: different approach: struct pci_controller.refcount
---
arch/powerpc/include/asm/pci-bridge.h |  2 ++
arch/powerpc/kernel/pci-common.c      | 15 ++++++++++++++-
arch/powerpc/platforms/pseries/pci.c  |  3 +++
3 files changed, 19 insertions(+), 1 deletion(-)

diff --git a/arch/powerpc/include/asm/pci-bridge.h b/arch/powerpc/include/asm/pci-bridge.h
index b5e88e4..9b11631 100644
--- a/arch/powerpc/include/asm/pci-bridge.h
+++ b/arch/powerpc/include/asm/pci-bridge.h

@@ -54,6 +54,7 @@ struct pci_controller_ops {
 */

struct pci_controller {
	struct pci_bus *bus;
+	struct pci_host_bridge *bridge; /* associated 'PHB' in PCI subsystem */
	char is_dynamic;
#ifdef CONFIG_PPC64
	int node;

@@ -301,6 +302,7 @@ 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_host_bridge_release(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 a5c0153..c5b5f60 100644
--- a/arch/powerpc/kernel/pci-common.c
+++ b/arch/powerpc/kernel/pci-common.c

@@ -145,11 +145,23 @@ void pcibios_free_controller(struct pci_controller *phb)

	list_del(&phb->list_node);
	spin_unlock(&hose_spinlock);

-	if (phb->is_dynamic)
+	/* if the associated pci_host_bridge has a release_fn(), rely on that. */
+	if (!phb->bridge->release_fn && phb->is_dynamic)
		kfree(phb);
}
EXPORT_SYMBOL_GPL(pcibios_free_controller);

+void pcibios_host_bridge_release(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);
+
+	if (phb->is_dynamic)
+		kfree(phb);
+}
+EXPORT_SYMBOL_GPL(pcibios_host_bridge_release);

I figure this is being exported so we can use it in cxl.

-- 
Andrew Donnellan              OzLabs, ADL Canberra
andrew.donnellan@au1.ibm.com  IBM Australia Limited