Re: [Qemu-devel] [PATCH] pci: add standard bridge device

[Wen Congyang]

At 09/07/2011 07:52 PM, Michael S. Tsirkin Write:
> On Wed, Sep 07, 2011 at 12:39:09PM +0800, Wen Congyang wrote:
>> At 09/06/2011 03:45 PM, Avi Kivity Write:
>>> On 09/06/2011 06:06 AM, Wen Congyang wrote:
>>>>>  Use the uio driver -
>>>>>  http://docs.blackfin.uclinux.org/kernel/generated/uio-howto/.  You
>>>> just
>>>>>  mmap() the BAR from userspace and play with it.
>>>>
>>>> When I try to bind ivshmem to uio_pci_generic, I get the following
>>>> messages:
>>>> uio_pci_generic 0000:01:01.0: No IRQ assigned to device: no support
>>>> for interrupts?
>>>>
>>>
>>> No idea what this means.
>>
>> PCI 3.0 6.2.4
>> For x86 based PCs, the values in this register correspond to IRQ numbers 
>> (0-15) of the standard dual
>> 8259 configuration. The value 255 is defined as meaning "unknown" or "no 
>> connection" to the interrupt
>> controller. Values between 15 and 254 are reserved.
>>
>> The register is interrupt line.
>>
>> I read the config of this device, the interrupt line is 0. It means that it 
>> uses the IRQ0.
>>
>> The following is the uio_pci_generic's code:
>> static int __devinit probe(struct pci_dev *pdev,
>>                         const struct pci_device_id *id)
>> {
>>      struct uio_pci_generic_dev *gdev;
>>      int err;
>>
>>      err = pci_enable_device(pdev);
>>      if (err) {
>>              dev_err(&pdev->dev, "%s: pci_enable_device failed: %d\n",
>>                      __func__, err);
>>              return err;
>>      }
>>
>>      if (!pdev->irq) {
>>              dev_warn(&pdev->dev, "No IRQ assigned to device: "
>>                       "no support for interrupts?\n");
>>              pci_disable_device(pdev);
>>              return -ENODEV;
>>      }
>> ...
>> }
>>
>> This function will be called when we write 'domain:bus:slot.function' to 
>> /sys/bus/pci/drivers/uio_pci_generic/bind.
>> pdev->irq is 0, it means the device uses IRQ0. But we refuse it. I do not 
>> why.
>>
>> To Michael S. Tsirkin
>> This code is writen by you. Do you know why you check whether pdev->irq is 0?
>>
>> Thanks
>> Wen Congyang
>>
>>>
> 
> Well I see this in linux:
> 
> /*
>  * Read interrupt line and base address registers.
>  * The architecture-dependent code can tweak these, of course.
>  */
> static void pci_read_irq(struct pci_dev *dev)
> {
>         unsigned char irq;
> 
>         pci_read_config_byte(dev, PCI_INTERRUPT_PIN, &irq);
>         dev->pin = irq;
>         if (irq)
>                 pci_read_config_byte(dev, PCI_INTERRUPT_LINE, &irq);
>         dev->irq = irq;
> }
> 
> Thus a device without an interrupt pin will get irq set to 0,
> and this seems the right way to detect such devices.
> I don't think PCI devices really use IRQ0 in practice,
> its probably used for PC things. More likely the system is
> misconfigured.  Try lspci -vv to see what went wrong.

Yes, the PCI device shoulde not use IRQ0. I debug qemu's code, and find the
PCI_INTERRUPT_LINE register is not set by qemu:
=============
Hardware watchpoint 6: ((uint8_t *) 0x164e410)[0x3c]

Old value = 0 '\000'
New value = 10 '\n'
pci_default_write_config (d=0x1653ed0, addr=60, val=10, l=1) at 
/home/wency/source/qemu/hw/pci.c:1115
1115            d->config[addr + i] &= ~(val & w1cmask); /* W1C: Write 1 to 
Clear */
Missing separate debuginfos, use: debuginfo-install 
cyrus-sasl-gssapi-2.1.23-8.el6.x86_64 cyrus-sasl-md5-2.1.23-8.el6.x86_64 
cyrus-sasl-plain-2.1.23-8.el6.x86_64 db4-4.7.25-16.el6.x86_64
(gdb) bt
#0  pci_default_write_config (d=0x1653ed0, addr=60, val=10, l=1) at 
/home/wency/source/qemu/hw/pci.c:1115
#1  0x00000000004d5827 in pci_host_config_write_common (pci_dev=0x1653ed0, 
addr=60, limit=256, val=10, len=1) at /home/wency/source/qemu/hw/pci_host.c:54
#2  0x00000000004d5939 in pci_data_write (s=0x15f95a0, addr=2147502140, val=10, 
len=1) at /home/wency/source/qemu/hw/pci_host.c:75
#3  0x00000000004d5b19 in pci_host_data_write (handler=0x15f9570, addr=3324, 
val=10, len=1) at /home/wency/source/qemu/hw/pci_host.c:125
#4  0x000000000063ee06 in ioport_simple_writeb (opaque=0x15f9570, addr=3324, 
value=10) at /home/wency/source/qemu/rwhandler.c:48
#5  0x0000000000470db9 in ioport_write (index=0, address=3324, data=10) at 
ioport.c:81
#6  0x00000000004717bc in cpu_outb (addr=3324, val=10 '\n') at ioport.c:273
#7  0x00000000005ef25d in kvm_handle_io (port=3324, data=0x7ffff7ff8000, 
direction=1, size=1, count=1) at /home/wency/source/qemu/kvm-all.c:834
#8  0x00000000005ef7e6 in kvm_cpu_exec (env=0x13da0d0) at 
/home/wency/source/qemu/kvm-all.c:976
#9  0x00000000005c1a7b in qemu_kvm_cpu_thread_fn (arg=0x13da0d0) at 
/home/wency/source/qemu/cpus.c:661
#10 0x00000032864077e1 in start_thread () from /lib64/libpthread.so.0
#11 0x00000032858e68ed in clone () from /lib64/libc.so.6
=============

If I put ivshmem on bus 0, the PCI_INTERRUPT_LINE register can be set. So I 
guess this register is set by bios.
I use the newest seabios, and PCI_INTERRUPT_LINE register is not set if the 
deivce is not on bus0.

# lspci -vv
00:00.0 Host bridge: Intel Corporation 440FX - 82441FX PMC [Natoma] (rev 02)
        Subsystem: Red Hat, Inc Qemu virtual machine
        Control: I/O+ Mem+ BusMaster- SpecCycle- MemWINV- VGASnoop- ParErr- 
Stepping- SERR- FastB2B- DisINTx-
        Status: Cap- 66MHz- UDF- FastB2B- ParErr- DEVSEL=fast >TAbort- <TAbort- 
<MAbort- >SERR- <PERR- INTx-

00:01.0 ISA bridge: Intel Corporation 82371SB PIIX3 ISA [Natoma/Triton II]
        Subsystem: Red Hat, Inc Qemu virtual machine
        Control: I/O+ Mem+ BusMaster- SpecCycle- MemWINV- VGASnoop- ParErr- 
Stepping- SERR- FastB2B- DisINTx-
        Status: Cap- 66MHz- UDF- FastB2B- ParErr- DEVSEL=medium >TAbort- 
<TAbort- <MAbort- >SERR- <PERR- INTx-

00:01.1 IDE interface: Intel Corporation 82371SB PIIX3 IDE [Natoma/Triton II] 
(prog-if 80 [Master])
        Subsystem: Red Hat, Inc Qemu virtual machine
        Control: I/O+ Mem+ BusMaster+ SpecCycle- MemWINV- VGASnoop- ParErr- 
Stepping- SERR- FastB2B- DisINTx-
        Status: Cap- 66MHz- UDF- FastB2B+ ParErr- DEVSEL=medium >TAbort- 
<TAbort- <MAbort- >SERR- <PERR- INTx-
        Latency: 0
        Region 0: [virtual] Memory at 000001f0 (32-bit, non-prefetchable) 
[size=8]
        Region 1: [virtual] Memory at 000003f0 (type 3, non-prefetchable) 
[size=1]
        Region 2: [virtual] Memory at 00000170 (32-bit, non-prefetchable) 
[size=8]
        Region 3: [virtual] Memory at 00000370 (type 3, non-prefetchable) 
[size=1]
        Region 4: I/O ports at d100 [size=16]
        Kernel driver in use: ata_piix
        Kernel modules: ata_piix

00:01.3 Bridge: Intel Corporation 82371AB/EB/MB PIIX4 ACPI (rev 03)
        Subsystem: Red Hat, Inc Qemu virtual machine
        Physical Slot: 1
        Control: I/O+ Mem+ BusMaster- SpecCycle- MemWINV- VGASnoop- ParErr- 
Stepping- SERR- FastB2B- DisINTx-
        Status: Cap- 66MHz- UDF- FastB2B+ ParErr- DEVSEL=medium >TAbort- 
<TAbort- <MAbort- >SERR- <PERR- INTx-
        Interrupt: pin A routed to IRQ 9
        Kernel driver in use: piix4_smbus
        Kernel modules: i2c-piix4

00:02.0 VGA compatible controller: Cirrus Logic GD 5446 (prog-if 00 [VGA 
controller])
        Subsystem: Red Hat, Inc Device 1100
        Physical Slot: 2
        Control: I/O+ Mem+ BusMaster- SpecCycle- MemWINV- VGASnoop- ParErr- 
Stepping- SERR- FastB2B- DisINTx-
        Status: Cap- 66MHz- UDF- FastB2B- ParErr- DEVSEL=fast >TAbort- <TAbort- 
<MAbort- >SERR- <PERR- INTx-
        Region 0: Memory at fc000000 (32-bit, prefetchable) [size=32M]
        Region 1: Memory at f8020000 (32-bit, non-prefetchable) [size=4K]
        Expansion ROM at f8000000 [disabled] [size=64K]
        Kernel modules: cirrusfb

00:03.0 Ethernet controller: Realtek Semiconductor Co., Ltd. 
RTL-8139/8139C/8139C+ (rev 20)
        Subsystem: Red Hat, Inc Device 1100
        Physical Slot: 3
        Control: I/O+ Mem+ BusMaster+ SpecCycle- MemWINV- VGASnoop- ParErr- 
Stepping- SERR- FastB2B- DisINTx-
        Status: Cap- 66MHz- UDF- FastB2B- ParErr- DEVSEL=fast >TAbort- <TAbort- 
<MAbort- >SERR- <PERR- INTx-
        Latency: 0, Cache Line Size: 64 bytes
        Interrupt: pin A routed to IRQ 11
        Region 0: I/O ports at d000 [size=256]
        Region 1: Memory at f8021000 (32-bit, non-prefetchable) [size=256]
        Expansion ROM at f8010000 [disabled] [size=64K]
        Kernel driver in use: 8139cp
        Kernel modules: 8139too, 8139cp

00:08.0 PCI bridge: Red Hat, Inc. Device 0001 (prog-if 00 [Normal decode])
        Physical Slot: 8
        Control: I/O+ Mem+ BusMaster+ SpecCycle- MemWINV- VGASnoop- ParErr- 
Stepping- SERR- FastB2B- DisINTx-
        Status: Cap- 66MHz+ UDF- FastB2B+ ParErr- DEVSEL=fast >TAbort- <TAbort- 
<MAbort- >SERR- <PERR- INTx-
        Latency: 0
        Bus: primary=00, secondary=01, subordinate=01, sec-latency=0
        I/O behind bridge: 0000c000-0000cfff
        Memory behind bridge: f0000000-f7ffffff
        Prefetchable memory behind bridge: fe000000-fe0fffff
        Secondary status: 66MHz+ FastB2B+ ParErr- DEVSEL=fast >TAbort- <TAbort- 
<MAbort- <SERR- <PERR-
        BridgeCtl: Parity- SERR- NoISA- VGA- MAbort- >Reset- FastB2B-
                PriDiscTmr- SecDiscTmr- DiscTmrStat- DiscTmrSERREn-

01:01.0 RAM memory: Red Hat, Inc Device 1110
        Subsystem: Red Hat, Inc Device 1100
        Control: I/O- Mem- BusMaster- SpecCycle- MemWINV- VGASnoop- ParErr- 
Stepping- SERR- FastB2B- DisINTx-
        Status: Cap- 66MHz- UDF- FastB2B- ParErr- DEVSEL=fast >TAbort- <TAbort- 
<MAbort- >SERR- <PERR- INTx-
        Interrupt: pin A routed to IRQ 0
        Region 0: Memory at f4000000 (32-bit, non-prefetchable) [disabled] 
[size=256]
        Region 2: Memory at f0000000 (32-bit, non-prefetchable) [disabled] 
[size=32M]
        Kernel modules: virtio_pci

01:01.1 RAM memory: Red Hat, Inc Device 1110
        Subsystem: Red Hat, Inc Device 1100
        Control: I/O- Mem- BusMaster- SpecCycle- MemWINV- VGASnoop- ParErr- 
Stepping- SERR- FastB2B- DisINTx-
        Status: Cap- 66MHz- UDF- FastB2B- ParErr- DEVSEL=fast >TAbort- <TAbort- 
<MAbort- >SERR- <PERR- INTx-
        Interrupt: pin A routed to IRQ 0
        Region 0: Memory at f4001000 (32-bit, non-prefetchable) [disabled] 
[size=256]
        Region 2: Memory at f2000000 (32-bit, non-prefetchable) [disabled] 
[size=32M]
        Kernel modules: virtio_pci


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