linux-kernel - Re: [PATCH 00/53] dyn_array/nr_irqs/sparse

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Date:	Thu, 14 Aug 2008 17:49:31 -0700
From:	"Yinghai Lu" <yhlu.kernel@...il.com>
To:	"Eric W. Biederman" <ebiederm@...ssion.com>
Cc:	"Ingo Molnar" <mingo@...e.hu>,
	"Thomas Gleixner" <tglx@...utronix.de>,
	"H. Peter Anvin" <hpa@...or.com>, linux-kernel@...r.kernel.org,
	"Alan Cox" <alan@...rguk.ukuu.org.uk>,
	"Andrew Morton" <akpm@...ux-foundation.org>
Subject: Re: [PATCH 00/53] dyn_array/nr_irqs/sparse_irq support v10

On Thu, Aug 14, 2008 at 5:11 PM, Eric W. Biederman
<ebiederm@...ssion.com> wrote:
> "Yinghai Lu" <yhlu.kernel@...il.com> writes:
>
>> find something interesting:
>>
>> found new irq_cfg for irq 20
>>  0 add_pin_to_irq: irq 20 --> apic 0 pin 20
>> assign_irq_vector: irq 20 vector 0x59 cpu  5
>> IOAPIC[0]: Set routing entry (0-20 -> 0x59 -> IRQ 20 Mode:1 Active:1)
>> found new irq_desc for irq 20
>> pci 0000:00:02.1: PCI INT B -> Link[LUS2] -> GSI 20 (level, low) -> IRQ 20
>>
>> IO APIC #0......
>> .... register #00: 00000000
>> .......    : physical APIC id: 00
>> .......    : Delivery Type: 0
>> .......    : LTS          : 0
>> .... register #01: 00170011
>> .......     : max redirection entries: 0017
>> .......     : PRQ implemented: 0
>> .......     : IO APIC version: 0011
>> .... register #02: 00000000
>> .......     : arbitration: 00
>> .... IRQ redirection table:
>>  NR Dst Mask Trig IRR Pol Stat Dmod Deli Vect:
>> ...
>>  14 09  1    1    0   1   0    0    0    59
>> ...
>>
>> ehci_hcd 0000:00:02.1: USB 2.0 started, EHCI 1.00, driver 10 Dec 2004
>> do_IRQ: cannot handle IRQ -1 vector 0x59 cpu 0
>> ------------[ cut here ]------------
>> Kernel BUG at 40206b11 [verbose debug info unavailable]
>> invalid opcode: 0000 [#1] SMP
>> Modules linked in:
>>
>> Pid: 70, comm: kasyncinit Not tainted (2.6.27-rc3-tip-00191-g98ccb89-dirty #23)
>> EIP: 0060:[<40206b11>] EFLAGS: 00010092 CPU: 0
>> EIP is at do_IRQ+0x6b/0xae
>> EAX: 00000032 EBX: 00001d28 ECX: 00003434 EDX: 00000046
>> ESI: 00000000 EDI: 00000059 EBP: c7a37d3c ESP: c7a37d14
>>  DS: 007b ES: 007b FS: 00d8 GS: 0000 SS: 0068
>> Process kasyncinit (pid: 70, ti=c7a36000 task=c79c9860 task.ti=c7a36000)
>> Stack: 40a74317 40814ea0 ffffffff 00000059 00000000 00000000 ffffffff c421bd20
>>        c7a37d9c c7a37dac c7a37d7c 4020555f c421bd20 00000000 c421bd20 c7a37d9c
>>        c7a37dac c7a37d7c 40b717f8 0000007b 0000007b 000000d8 ffffffa6 4080db6c
>> Call Trace:
>>  [<4020555f>] ? common_interrupt+0x23/0x28
>>
>>
>> it is on 16cores system with 32bit bigsmp, so it is using phy_flat
>> cpu 5 has apicid 9, and ioapic reg setting right with Dmod= 0 ( phys)
>>
>> but io_apic controller deliver that interrupt to cpu0 (with apicid =
>> 4) instead of cpu 5 (with apic id = 9)
>>
>> look at the 64 bit, TARGET_CPUS for phys_flat is cpu_online_map
>>
>> and 32bit bigsmp TARGET_CPUS is only one cpu set and rotating with online cpu...
>>
>> Change 32bit bigsmp TARGE_CPUS ?
>
> Set vector_allocation_domain to CPU_MASK_ALL on 32bit.  That doesn't give us
> the benefit of per cpu vectors right now, but in my research there has not
> been a 32bit kernel yet that has needed it.  We have never shared vectors
> between 2 gsi on 32bit x86, we have only collapsed the irq space.

TARGET_CPUS only used by ioapic_xx.c

vector_allocator_domain will return cpumask_of_cpu(cpu)..

>
> On x86_64 before I did the per cpu vectors there were machines that
> combined multiple interrupt sources (gsi) into the same irq.  So
> x86_64 has needed the per cpu vectors.
>
> Which means in practice that the irq compression on x86_32 was just a hack to
> with not having enough irq_desc entries.  I wish I had realized that last
> time we were talking, as we could have unilaterally ripped out all of that
> code as completely unnecessary on x86 and just bumped NR_IRQS to 1024 on
> the boxes that had more than 256 gsis.

now 32bit and 64bit is the same page now... (bigsmp == phys_flat)...

will continue to merge io_apic_xx.c

YH
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