linux-kernel - Re: oops in ioapic_write

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Date:	Tue, 03 Aug 2010 02:01:03 -0700
From:	Yinghai Lu <yinghai@...nel.org>
To:	"Eric W. Biederman" <ebiederm@...ssion.com>
CC:	Dave Airlie <airlied@...il.com>,
	LKML <linux-kernel@...r.kernel.org>, Ingo Molnar <mingo@...e.hu>
Subject: Re: oops in ioapic_write_entry

On 08/03/2010 01:56 AM, Eric W. Biederman wrote:
> Yinghai Lu <yinghai@...nel.org> writes:
> 
>> On 08/03/2010 01:00 AM, Eric W. Biederman wrote:
>>> Yinghai Lu <yinghai@...nel.org> writes:
>>>
>>>>>> Index: linux-2.6/arch/x86/kernel/apic/io_apic.c
>>>>>> ===================================================================
>>>>>> --- linux-2.6.orig/arch/x86/kernel/apic/io_apic.c
>>>>>> +++ linux-2.6/arch/x86/kernel/apic/io_apic.c
>>>>>> @@ -1029,10 +1029,7 @@ static int pin_2_irq(int idx, int apic,
>>>>>>  	} else {
>>>>>>  		u32 gsi = mp_gsi_routing[apic].gsi_base + pin;
>>>>>>  
>>>>>> -		if (gsi >= NR_IRQS_LEGACY)
>>>>>> -			irq = gsi;
>>>>>> -		else
>>>>>> -			irq = gsi_top + gsi;
>>>>>> +		irq = gsi_to_irq(gsi);
>>>>>>  	}
>>>>>>  
>>>>>>  #ifdef CONFIG_X86_32
>>>>
>>>> what is the point for making irq = gsi_top + gsi when mptable is used instead of acpi?
>>>
>>> Because it is only convention that when mptables are used that the
>>> first apic pins 0-15 are the ISA irqs.  This thread witnessed and a
>>> pci irq that came in pin < 16 that was not an ISA irq.  The truly rare
>>> and exotic case would be for the ISA irqs to be outside the first 16
>>> ioapic pins but the es7000 did exactly that.
>>
>> nvidia chipset if acpi is enabled, external pci device will use ioapic from 16 to 23.
>>
>> if mptable is used, external pci device will not use pin from 16 to 23..., and lot of devices will share same pin.
> 
> Exactly.  Pins < 16 are not necessarily ISA irqs, and can be possibly
> shared level triggered PCI irqs.  Unfortunately there are strange
> boards like the es7000 where pins > 16 are ISA irqs.
> 
> The other thing that is gained by having pin_2_irq always remap pins <
> 16 is we can get away with the numerous hard codes in the arch/x86 and elsewhere
> that assume irq < 16 is an ISA irq.

how about this one ?

---
 arch/x86/kernel/apic/io_apic.c |   31 ++++++++++++++++++++++++++++---
 1 file changed, 28 insertions(+), 3 deletions(-)

Index: linux-2.6/arch/x86/kernel/apic/io_apic.c
===================================================================
--- linux-2.6.orig/arch/x86/kernel/apic/io_apic.c
+++ linux-2.6/arch/x86/kernel/apic/io_apic.c
@@ -1013,6 +1013,28 @@ static inline int irq_trigger(int idx)
 	return MPBIOS_trigger(idx);
 }
 
+static int shared_with_legacy(int apic, int pin)
+{
+	int i;
+
+	for (i = 0; i < mp_irq_entries; i++) {
+		int bus = mp_irqs[i].srcbus;
+
+		if (!test_bit(bus, mp_bus_not_pci))
+			continue;
+
+		if (mp_ioapics[apic].apicid != mp_irqs[i].dstapic)
+			continue;
+
+		if (mp_irqs[i].dstirq != pin)
+			continue;
+
+		return mp_irqs[i].srcbusirq;
+	}
+
+	return -1;
+}
+
 static int pin_2_irq(int idx, int apic, int pin)
 {
 	int irq;
@@ -1029,10 +1051,13 @@ static int pin_2_irq(int idx, int apic,
 	} else {
 		u32 gsi = mp_gsi_routing[apic].gsi_base + pin;
 
-		if (gsi >= NR_IRQS_LEGACY)
+		if (gsi >= NR_IRQS_LEGACY) {
 			irq = gsi;
-		else
-			irq = gsi_top + gsi;
+		} else {
+			irq = shared_with_legacy(apic, pin);
+			if (irq < 0)
+				irq = gsi_top + gsi;
+		}
 	}
 
 #ifdef CONFIG_X86_32
--
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