UIO RTE_INTR_MODE_NONE issue.

From: Prathap Thammanna <Prathap.Thammanna@radisys.com>
To: "dev@dpdk.org" <dev@dpdk.org>
Subject: UIO RTE_INTR_MODE_NONE issue.
Date: Thu, 2 Jul 2015 03:23:42 +0000	[thread overview]
Message-ID: <BY2PR0801MB1606DD23FD54CAF51FE60159EF970@BY2PR0801MB1606.namprd08.prod.outlook.com> (raw)

Hi:

If INTX fails, igb_uio falls back to running without IRQ ( refer to the implementation in igbuio_pci_probe).
On QEMU 0.12.0, the INTX seems to have broken, and the intr_mode falls to RTE_INTR_MODE_NONE
However this sets the udev->info.irq = 0;

Setting of udev->info.irq  to '0' does not work on 2.6.36 and lower kernels, because the UIO_IRQ_NONE is defined as

#define UIO_IRQ_NONE   -2

Because the udev->info.irq  is set to '0', on 2.6.36 and below implementation, the __uio_register_device invokes request_irq

if (idev->info->irq >= 0) {
 ret = request_irq(idev->info->irq, uio_interrupt,
and it fails with the following dump

IRQ handler type mismatch for IRQ 0
current handler: timer
Pid: 3106, comm: dpdk_nic_bind.p Not tainted 2.6.32-504.23.4.el6.x86_64 #1
Call Trace:
[<ffffffff810ebd62>] ? __setup_irq+0x382/0x3c0
[<ffffffffa033f2a0>] ? uio_interrupt+0x0/0x48 [uio]
[<ffffffff810ec563>] ? request_threaded_irq+0x133/0x230
[<ffffffffa033f193>] ? __uio_register_device+0x553/0x610 [uio]
[<ffffffffa0345652>] ? igbuio_pci_probe+0x3a7/0x4a0 [igb_uio]
[<ffffffff8128e58a>] ? kobject_get+0x1a/0x30
[<ffffffff812af417>] ? local_pci_probe+0x17/0x20
[<ffffffff812b0601>] ? pci_device_probe+0x101/0x120
[<ffffffff8136c992>] ? driver_sysfs_add+0x62/0x90
[<ffffffff8136cc2c>] ? driver_probe_device+0x9c/0x3e0
[<ffffffff8136bd6a>] ? driver_bind+0xca/0x110
[<ffffffff8136ae3c>] ? drv_attr_store+0x2c/0x30
[<ffffffff8120a4c5>] ? sysfs_write_file+0xe5/0x170
[<ffffffff8118e1c8>] ? vfs_write+0xb8/0x1a0
[<ffffffff8118eb91>] ? sys_write+0x51/0x90
[<ffffffff8100b0f2>] ? system_call_fastpath+0x16/0x1b
igb_uio 0000:00:03.0: PCI INT A disabled
igb_uio: probe of 0000:00:03.0 failed with error -16

On kernel 2.6.37 and above, the definition is,

#define UIO_IRQ_NONE   0

And the check is,

if (info->irq && (info->irq != UIO_IRQ_CUSTOM)) {
               ret = request_irq(info->irq, uio_interrupt,
                                 info->irq_flags, info->name, idev);

So to handle the 'RTE_INTR_MODE_NONE' in these different kernel versions,
We are proposing the following change to the code in igbuio_pci_probe function,

case RTE_INTR_MODE_NONE:
                udev->mode = RTE_INTR_MODE_NONE;
#if LINUX_VERSION_CODE < KERNEL_VERSION(2, 6, 37)
         udev->info.irq = -2;
#else
        udev->info.irq = 0;
#endif

Please let us  know your opinion. If it is correct, we will go ahead and generate a patch for review.

Regards,
Prathap