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authorKonrad Rzeszutek Wilk <konrad.wilk@oracle.com>2010-10-18 10:49:10 -0400
committerKonrad Rzeszutek Wilk <konrad.wilk@oracle.com>2010-10-18 10:49:10 -0400
commit3a69e9165a271b026c7149886b96ab0cc2e9a36b (patch)
tree9a51f952039745feee23d21b3b6b3834aabeef0c /include/xen
parentxen: statically initialize cpu_evtchn_mask_p (diff)
downloadlinux-dev-3a69e9165a271b026c7149886b96ab0cc2e9a36b.tar.xz
linux-dev-3a69e9165a271b026c7149886b96ab0cc2e9a36b.zip
xen: Find an unbound irq number in reverse order (high to low).
In earlier Xen Linux kernels, the IRQ mapping was a straight 1:1 and the find_unbound_irq started looking around 256 for open IRQs and up. IRQs from 0 to 255 were reserved for PCI devices. Previous to this patch, the 'find_unbound_irq' started looking at get_nr_hw_irqs() number. For privileged domain where the ACPI information is available that returns the upper-bound of what the GSIs. For non-privileged PV domains, where ACPI is no-existent the get_nr_hw_irqs() reports the IRQ_LEGACY (16). With PCI passthrough enabled, and with PCI cards that have IRQs pinned to a higher number than 16 we collide with previously allocated IRQs. Specifically the PCI IRQs collide with the IPI's for Xen functions (as they are allocated earlier). For example: 00:00.11 USB Controller: ATI Technologies Inc SB700 USB OHCI1 Controller (prog-if 10 [OHCI]) ... Interrupt: pin A routed to IRQ 18 [root@localhost ~]# cat /proc/interrupts | head CPU0 CPU1 CPU2 16: 38186 0 0 xen-dyn-virq timer0 17: 149 0 0 xen-dyn-ipi spinlock0 18: 962 0 0 xen-dyn-ipi resched0 and when the USB controller is loaded, the kernel reports: IRQ handler type mismatch for IRQ 18 current handler: resched0 One way to fix this is to reverse the logic when looking for un-used IRQ numbers and start with the highest available number. With that, we would get: CPU0 CPU1 CPU2 ... snip .. 292: 35 0 0 xen-dyn-ipi callfunc0 293: 3992 0 0 xen-dyn-ipi resched0 294: 224 0 0 xen-dyn-ipi spinlock0 295: 57183 0 0 xen-dyn-virq timer0 NMI: 0 0 0 Non-maskable interrupts .. snip .. And interrupts for PCI cards are now accessible. This patch also includes the fix, found by Ian Campbell, titled "xen: fix off-by-one error in find_unbound_irq." [v2: Added an explanation in the code] [v3: Rebased on top of tip/irq/core] Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com> Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
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