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

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

[Ranran]

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

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

[Stephen Hemminger]

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

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

[Ranran]

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.

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

[Stephen Hemminger]

On Sat, 30 Nov 2019 19:49:16 +0200
Ranran <ranshalit@gmail.com> wrote:

> > >
> > > 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
> >  

Actually UIO PCI generic does support interrupts but only legacy INTx,
it does not support MSI or MSI-x modes.

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

[Ranran]

בתאריך יום א׳, 1 בדצמ׳ 2019, 19:07, מאת Stephen Hemminger ‏<
stephen@networkplumber.org>:

> On Sat, 30 Nov 2019 19:49:16 +0200
> Ranran <ranshalit@gmail.com> wrote:
>
> > > >
> > > > 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
> > >
>
> Actually UIO PCI generic does support interrupts but only legacy INTx,
> it does not support MSI or MSI-x modes.
>

Right.
The device I work with is FPGA xilinx which should support INTx. Yet, even
though irqhandler is called, it does not pass pci_check_and_mask_intx, and
therefore irq is not handled, as I written in the original post.

Thanks

>

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

[Stephen Hemminger]

On Sun, 1 Dec 2019 20:16:59 +0200
Ranran <ranshalit@gmail.com> wrote:

> בתאריך יום א׳, 1 בדצמ׳ 2019, 19:07, מאת Stephen Hemminger ‏<
> stephen@networkplumber.org>:
> 
> > On Sat, 30 Nov 2019 19:49:16 +0200
> > Ranran <ranshalit@gmail.com> wrote:
> >
> > > > >
> > > > > 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
> > > >
> >
> > Actually UIO PCI generic does support interrupts but only legacy INTx,
> > it does not support MSI or MSI-x modes.
> >
> 
> Right.
> The device I work with is FPGA xilinx which should support INTx. Yet, even
> though irqhandler is called, it does not pass pci_check_and_mask_intx, and
> therefore irq is not handled, as I written in the original post.

Your problem may be that the FPGA is not correctly implementing the PCI spec.
I saw this before with VMWare.

The kernel expects to be able to read the PCI_COMMAND register to
see if IRQ is pending and then write back INTX_DISABLE bit.