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x86/ioapic: Check attr against the previous setting when programmed more than once

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When programming ioapic pinX more than once, current code
does not check whether the later attr (trigger & polarity) is the
same as the former or not.

This causes broken semantics which can be observed in a qemu q35
machine, where ioapic's ioredtbl[x] can never be set as low-active,
even if the hpet driver registered it.

And hpet driver may share a high-level active IRQ line with other
devices. So in qemu, when hpet-dev asserts low-level as kernel
expects, the kernel has no response.

With this patch, we can observe an ioredtbl[x] set as low-active
for hpet.

Fix it by reporting -EBUSY to the caller, when attr is different.

Signed-off-by: Liu Ping Fan <pingfank@linux.vnet.ibm.com>
Cc: Kevin Hao <haokexin@gmail.com>
Cc: Len Brown <len.brown@intel.com>
Cc: Yinghai Lu <yinghai@kernel.org>
Link: http://lkml.kernel.org/r/1377248327-19633-1-git-send-email-pingfank@linux.vnet.ibm.com
[ Made small readability edits to both the changelog and the code. ]
Signed-off-by: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
Liu Ping Fan
2013-08-23 16:58:47 +08:00
committed by Ingo Molnar
parent 17405453f4
commit 25aa295797
2 changed files with 10 additions and 4 deletions
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9
arch/x86/kernel/apic/io_apic.c
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@@ -3380,12 +3380,15 @@ int io_apic_setup_irq_pin_once(unsigned int irq, int node,
{
unsigned int ioapic_idx = attr->ioapic, pin = attr->ioapic_pin;
int ret;
struct IO_APIC_route_entry orig_entry;
/* Avoid redundant programming */
if (test_bit(pin, ioapics[ioapic_idx].pin_programmed)) {
pr_debug("Pin %d-%d already programmed\n",
mpc_ioapic_id(ioapic_idx), pin);
return 0;
pr_debug("Pin %d-%d already programmed\n", mpc_ioapic_id(ioapic_idx), pin);
orig_entry = ioapic_read_entry(attr->ioapic, pin);
if (attr->trigger == orig_entry.trigger && attr->polarity == orig_entry.polarity)
return 0;
return -EBUSY;
}
ret = io_apic_setup_irq_pin(irq, node, attr);
if (!ret)