[Xen-devel] [PATCH][PVOPS] preserve chip_data when initializing irq in xen_allocate_pirq

[Ronny Hegewald <ronny.hegewald@xxxxxxxxx>]

When running latest xen/stable-2.6.31.x as dom0 it crashes during boot with a 
stacktrace that looks like this.

        do_page_fault
        add_pin_to_irq_node
        setup_IO_APIC_irq_extra
        sysfs_create_group
        acpi_ev_sci_xrupt_handler
        acpi_sci_to_irq
        acpi_os_install_interrupt_handler
        acpi_ev_install_sci_handler
        acpi_enable_subsystem
        acpi_init
        pci_slot_init
        acpi_init
        do_one_initcall
        kernel_init

This only happens when the kernel is configured with CONFIG_SPARSE_IRQ=n.
 
This crash appeared since the upstream patch 

        x86: Fix SCI on IOAPIC != 0 
(http://git.kernel.org/?p=linux/kernel/git/jeremy/xen.git;a=commitdiff;h=d539e5576605d048e6aeb21cbe3a8e71dc5eea81)

from the stable 2.6.31.13 series.

The crash happens in add_pin_to_irq_node because irq_cfg, that is taken from 
irq_desc.chip_data, is null.

In xen/stable-2.6.32.x this doesnt happen currently, because of the removement 
of the xen apic-code. This has the effect that the call to mp_find_ioapic in 
setup_IO_APIC_irq_extra returns -1 and the function aborts before the code is 
reached where the crash happens.

The root-problem is that in xen_allocate_pirq the chip_data is cleared by the 
call to dynamic_irq_init. The attached patch fixes this by reinserting 
chip_data after the call to dynamic_irq_init.

For 2.6.32 the code can be simplified so i attached a separate patch for 
xen/stable-2.6.32.x 

========== patch for xen/stable-2.6.31.x

Preserve irq_desc.chip_data when calling dynamic_irq_init, as its needed later 
in setup_IO_APIC_irq_extra.

Signed-off-by: Ronny.Hegewald@xxxxxxxxx

--- drivers/xen/events.c.org    2010-09-20 21:07:49.000000000 +0000
+++ drivers/xen/events.c        2010-09-29 01:11:20.000000000 +0000
@@ -559,6 +559,8 @@ int xen_allocate_pirq(unsigned gsi, int 
 {
        int irq;
        struct physdev_irq irq_op;
+       struct irq_desc* desc;
+       void* chip_data;
 
        spin_lock(&irq_mapping_update_lock);
 
@@ -573,8 +575,10 @@ int xen_allocate_pirq(unsigned gsi, int 
         * we are using the !xen_initial_domain() to drop in the function.*/
        if (identity_mapped_irq(gsi) || !xen_initial_domain()) {
                irq = gsi;
-               irq_to_desc_alloc_node(irq, 0);
+               desc = irq_to_desc_alloc_node(irq, 0);
+               chip_data = desc->chip_data; 
                dynamic_irq_init(irq);
+               desc->chip_data = chip_data; 
        } else
                irq = find_unbound_irq();


========== patch for xen/stable-2.6.32.x

Preserve irq_desc.chip_data when calling dynamic_irq_init, as its needed later 
in setup_IO_APIC_irq_extra.

Signed-off-by: Ronny.Hegewald@xxxxxxxxx

--- drivers/xen/events.c.org    2010-09-28 23:45:41.000000000 +0000
+++ drivers/xen/events.c        2010-09-28 23:46:11.000000000 +0000
@@ -602,7 +602,7 @@
        if (identity_mapped_irq(gsi) || !xen_initial_domain()) {
                irq = gsi;
                irq_to_desc_alloc_node(irq, 0);
-               dynamic_irq_init(irq);
+               dynamic_irq_init_keep_chip_data(irq);
        } else
                irq = find_unbound_irq();



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