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Konrad Rzeszutek Wilk committed 2531d64b6fe
xen/x86: Workaround 'x86/ioapic: Add register level checks to detect bogus io-apic entries' The above mentioned patch checks the IOAPIC and if it contains -1, then it unmaps said IOAPIC. But under Xen we get this: BUG: unable to handle kernel NULL pointer dereference at 0000000000000040 IP: [<ffffffff8134e51f>] xen_irq_init+0x1f/0xb0 PGD 0 Oops: 0002 [#1] SMP CPU 0 Modules linked in: Pid: 1, comm: swapper/0 Not tainted 3.2.10-3.fc16.x86_64 #1 Dell Inc. Inspiron 1525 /0U990C RIP: e030:[<ffffffff8134e51f>] [<ffffffff8134e51f>] xen_irq_init+0x1f/0xb0 RSP: e02b: ffff8800d42cbb70 EFLAGS: 00010202 RAX: 0000000000000000 RBX: 00000000ffffffef RCX: 0000000000000001 RDX: 0000000000000040 RSI: 00000000ffffffef RDI: 0000000000000001 RBP: ffff8800d42cbb80 R08: ffff8800d6400000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000000 R12: 00000000ffffffef R13: 0000000000000001 R14: 0000000000000001 R15: 0000000000000010 FS: 0000000000000000(0000) GS:ffff8800df5fe000(0000) knlGS:0000000000000000 CS: e033 DS: 0000 ES: 0000 CR0:000000008005003b CR2: 0000000000000040 CR3: 0000000001a05000 CR4: 0000000000002660 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000400 Process swapper/0 (pid: 1, threadinfo ffff8800d42ca000, task ffff8800d42d0000) Stack: 00000000ffffffef 0000000000000010 ffff8800d42cbbe0 ffffffff8134f157 ffffffff8100a9b2 ffffffff8182ffd1 00000000000000a0 00000000829e7384 0000000000000002 0000000000000010 00000000ffffffff 0000000000000000 Call Trace: [<ffffffff8134f157>] xen_bind_pirq_gsi_to_irq+0x87/0x230 [<ffffffff8100a9b2>] ? check_events+0x12+0x20 [<ffffffff814bab42>] xen_register_pirq+0x82/0xe0 [<ffffffff814bac1a>] xen_register_gsi.part.2+0x4a/0xd0 [<ffffffff814bacc0>] acpi_register_gsi_xen+0x20/0x30 [<ffffffff8103036f>] acpi_register_gsi+0xf/0x20 [<ffffffff8131abdb>] acpi_pci_irq_enable+0x12e/0x202 [<ffffffff814bc849>] pcibios_enable_device+0x39/0x40 [<ffffffff812dc7ab>] do_pci_enable_device+0x4b/0x70 [<ffffffff812dc878>] __pci_enable_device_flags+0xa8/0xf0 [<ffffffff812dc8d3>] pci_enable_device+0x13/0x20 The reason we are dying is b/c the call acpi_get_override_irq() is used, which returns the polarity and trigger for the IRQs. That function calls mp_find_ioapics to get the 'struct ioapic' structure - which along with the mp_irq[x] is used to figure out the default values and the polarity/trigger overrides. Since the mp_find_ioapics now returns -1 [b/c the IOAPIC is filled with 0xffffffff], the acpi_get_override_irq() stops trying to lookup in the mp_irq[x] the proper INT_SRV_OVR and we can't install the SCI interrupt. The proper fix for this is going in v3.5 and adds an x86_io_apic_ops struct so that platforms can override it. But for v3.4 lets carry this work-around. This patch does that by providing a slightly different variant of the fake IOAPIC entries. Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>