Re: [dpdk-dev] Interrupt is catched in kernel, but not handled

[Ranran <ranshalit@gmail.com>]

בתאריך שבת, 30 בנוב׳ 2019, 18:51, מאת Stephen Hemminger ‏<
stephen@networkplumber.org>:

> On Sat, 30 Nov 2019 10:40:38 +0200
> Ranran <ranshalit@gmail.com> wrote:
>
> > Hello,
> >
> > This is not a specific dpdk question, but more related to using of
> > uio_pci_generic.
> > Unfortunately, I don't find any examples of using the generic driver
> > from userspace, so this is my last hope to reach a suggestion.
> >
> > I installed centos8 , and I use uio_pci_generic, in order to
> > communicate with FPGA (Xilinx) through PCIe in userspace.
> >
> > The cpu is ATOM cpu.
> >
> > I first install the driver:
> > echo "10ee 0007" > /sys/bus/pci/drivers/uio_pci_generic/new_id
> >
> > Reading from BAR works perfectly but there is an issue with interrupts.
> >
> > I use userspace application which wait for interrupt, exactly as
> > described in code example here:
> > https://www.kernel.org/doc/html/v4.1...uio-howto.html
> >
> >
> > I than trigger an interrupt from FPGA, but no print from the userspace
> > application is given and there is an exception:
> >
> > irq 23: nobody cared (try booting with the "irqpoll" option)
> > [ 91.030760] CPU: 2 PID: 0 Comm: swapper/2 Not tainted 4.18.16 #6
> > [ 91.037037] Hardware name: /conga-MA5, BIOS MA50R000 10/30/2019
> > [ 91.043302] Call Trace:
> > [ 91.045881] <IRQ>
> > [ 91.048002] dump_stack+0x5c/0x80
> > [ 91.051464] __report_bad_irq+0x35/0xaf
> > [ 91.055465] note_interrupt.cold.9+0xa/0x63
> > [ 91.059823] handle_irq_event_percpu+0x68/0x70
> > [ 91.064470] handle_irq_event+0x37/0x57
> > [ 91.068481] handle_fasteoi_irq+0x97/0x150
> > [ 91.072758] handle_irq+0x1a/0x30
> > [ 91.076230] do_IRQ+0x44/0xd0
> > [ 91.079333] common_interrupt+0xf/0xf
> > [ 91.083154] </IRQ>
> > [ 91.085360] RIP: 0010:cpuidle_enter_state+0x7d/0x220
> > [ 91.090563] Code: e8 18 1a 45 00 41 89 c4 e8 d0 50 b1 ff 65 8b 3d d9
> > db e5 5f e8 44 4f b1 ff 31 ff 48 89 c3 e8 ea 61 b1 ff fb 66 0f 1f 44
> > 00 00 <48> b8 ff ff ff ff f3 01 00 00 4c 29 eb ba ff ff ff 7f 48 89 d9
> > 48
> > [ 91.110283] RSP: 0018:ffffb20e806b7ea8 EFLAGS: 00000286 ORIG_RAX:
> > ffffffffffffffda
> > [ 91.118203] RAX: ffff90133fd214c0 RBX: 00000015316faa09 RCX:
> 000000000000001f
> > [ 91.125662] RDX: 00000015316faa09 RSI: 0000000000000000 RDI:
> 0000000000000000
> > [ 91.133133] RBP: ffff90133fd2b300 R08: 0000011741eb842c R09:
> 0000000000000006
> > [ 91.140605] R10: 00000000ffffffff R11: ffff90133fd205a8 R12:
> 0000000000000001
> > [ 91.148068] R13: 00000015316f98b9 R14: 0000000000000001 R15:
> 0000000000000000
> > [ 91.155523] ? cpuidle_enter_state+0x76/0x220
> > [ 91.160088] do_idle+0x221/0x260
> > [ 91.163470] cpu_startup_entry+0x6a/0x70
> > [ 91.167588] start_secondary+0x1a4/0x1f0
> > [ 91.171676] secondary_startup_64+0xb7/0xc0
> > [ 91.176043] handlers:
> > [ 91.178419] [<00000000ec05b056>] uio_interrupt
> > [ 91.183054] Disabling IRQ #23
> >
> >
> > So, I started debugging this issue in kernel uio_pci_generic.c code,
> > and according to the prints below, it seems that irq is catched but
> > not delivered to userspace:
> >
> >
> >
> > static irqreturn_t irqhandler(int irq, struct uio_info *info)
> > {
> > struct uio_pci_generic_dev *gdev = to_uio_pci_generic_dev(info);
> > printk("i'm here 1\n"); <<--- this is printed
> > if (!pci_check_and_mask_intx(gdev->pdev))
> > return IRQ_NONE;
> > printk("i'm here 2\n"); <<--- but this is NOT printed
> > /* UIO core will signal the user process. */
> > return IRQ_HANDLED;
> > }
> > Reading documentation, I see that pci_check_and_mask_intx is actually
> > checking if interrupt bit is set in configuration space. Since it
> > seems to return 0 ,it should mean that it finds that this bit is not
> > enabled.
> > But how can it be that irq is triggered and status bit is not enabled
> > in configuration space ?
> >
> > The device appear as following with lspci -vv:
> >
> >
> > 02:00.0 RAM memory: Xilinx Corporation Default PCIe endpoint ID
> > Subsystem: Xilinx Corporation Default PCIe endpoint ID
> > 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 23
> > Region 0: Memory at 91200000 (32-bit, non-prefetchable) [size=1M]
> > Capabilities: [40] Power Management version 3
> > Flags: PMEClk- DSI+ D1- D2- AuxCurrent=0mA
> PME(D0-,D1-,D2-,D3hot-,D3cold-)
> > Status: D0 NoSoftRst+ PME-Enable- DSel=0 DScale=0 PME-
> > Capabilities: [48] MSI: Enable- Count=1/1 Maskable- 64bit+
> > Address: 0000000000000000 Data: 0000
> > Capabilities: [58] Express (v1) Endpoint, MSI 00
> > DevCap: MaxPayload 256 bytes, PhantFunc 1, Latency L0s <64ns, L1 <1us
> > ExtTag+ AttnBtn- AttnInd- PwrInd- RBE+ FLReset- SlotPowerLimit 10.000W
> > DevCtl: Report errors: Correctable- Non-Fatal- Fatal- Unsupported-
> > RlxdOrd+ ExtTag+ PhantFunc- AuxPwr- NoSnoop+
> > MaxPayload 256 bytes, MaxReadReq 512 bytes
> > DevSta: CorrErr- UncorrErr- FatalErr- UnsuppReq- AuxPwr- TransPend-
> > LnkCap: Port #0, Speed 2.5GT/s, Width x1, ASPM L0s, Exit Latency L0s
> unlimited
> > ClockPM- Surprise- LLActRep- BwNot- ASPMOptComp-
> > LnkCtl: ASPM Disabled; RCB 64 bytes Disabled- CommClk+
> > ExtSynch- ClockPM- AutWidDis- BWInt- AutBWInt-
> > LnkSta: Speed 2.5GT/s, Width x1, TrErr- Train- SlotClk+ DLActive-
> > BWMgmt- ABWMgmt-
> > Capabilities: [100 v1] Device Serial Number 00-00-00-00-00-00-00-00
> > Kernel driver in use: uio_pci_generic
> >
> >
> > I also verified that there are no additional irq numbered 23 except
> > for our device.
> >
> > How can it be that irq is catched, but not delivered to userspace ?
> > Any suggestion is much appreciated,
> >
> > ran
>
> UIO PCI generic does not support interrupts.
> You need to use VFIO (preferred) or igb_uio
>


Hi,
But according to linux documentation link
https://www.kernel.org/doc/html/v4.1...uio-howto.html
uio generic should supports interrupts.