[tip:x86/urgent] x86/PCI: Implement pcibios_release_device to release IRQ from IOAPIC

[tip-bot for Rui Wang]

Commit-ID:  153654dbe595a68845ba14d5b0bfe299fa6a7e99
Gitweb:     http://git.kernel.org/tip/153654dbe595a68845ba14d5b0bfe299fa6a7e99
Author:     Rui Wang <rui.y.wang@xxxxxxxxx>
AuthorDate: Tue, 28 Feb 2017 21:34:28 +0800
Committer:  Thomas Gleixner <tglx@xxxxxxxxxxxxx>
CommitDate: Wed, 1 Mar 2017 10:51:41 +0100

x86/PCI: Implement pcibios_release_device to release IRQ from IOAPIC

The revert of 991de2e59090 ("PCI, x86: Implement pcibios_alloc_irq()
and pcibios_free_irq()") causes a problem for IOAPIC hotplug. The
problem is that IRQs are allocated and freed in pci_enable_device()
and pci_disable_device(). But there are some drivers which don't call
pci_disable_device(), and they have good reasons not calling it, so
if they're using IOAPIC their IRQs won't have a chance to be released
from the IOAPIC. When this happens IOAPIC hot-removal fails with a
kernel stack dump and an error message like this:

  [149335.697989] pin16 on IOAPIC2 is still in use.

It turns out that we can fix it in a different way without moving IRQ
allocation into pcibios_alloc_irq(), thus avoiding the regression of
991de2e59090. We can keep the allocation and freeing of IRQs as is
within pci_enable_device()/pci_disable_device(), without breaking any
previous assumption of the rest of the system, keeping compatibility
with both the legacy and the modern drivers. We can accomplish this by
implementing the existing __weak hook of pcibios_release_device() thus
when a pci device is about to be deleted we get notified in the hook
and take the chance to release its IRQ, if any, from the IOAPIC.

Implement pcibios_release_device() for x86 to release any IRQ not released
by the driver.

Signed-off-by: Rui Wang <rui.y.wang@xxxxxxxxx>
Cc: tony.luck@xxxxxxxxx
Cc: linux-pci@xxxxxxxxxxxxxxx
Cc: rjw@xxxxxxxxxxxxx
Cc: linux-acpi@xxxxxxxxxxxxxxx
Cc: fengguang.wu@xxxxxxxxx
Cc: helgaas@xxxxxxxxxx
Cc: kbuild-all@xxxxxx
Cc: bhelgaas@xxxxxxxxxx
Link: http://lkml.kernel.org/r/1488288869-31290-2-git-send-email-rui.y.wang@xxxxxxxxx
Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>

---
 arch/x86/pci/common.c | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/arch/x86/pci/common.c b/arch/x86/pci/common.c
index 0cb52ae..190e718 100644
--- a/arch/x86/pci/common.c
+++ b/arch/x86/pci/common.c
@@ -735,6 +735,15 @@ void pcibios_disable_device (struct pci_dev *dev)
 		pcibios_disable_irq(dev);
 }
 
+#ifdef CONFIG_ACPI_HOTPLUG_IOAPIC
+void pcibios_release_device(struct pci_dev *dev)
+{
+	if (atomic_dec_return(&dev->enable_cnt) >= 0)
+		pcibios_disable_device(dev);
+
+}
+#endif
+
 int pci_ext_cfg_avail(void)
 {
 	if (raw_pci_ext_ops)