linux-kernel - Re: [PATCH] selftest: drivers: Add support to check duplicate hwirq

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Message-ID: <dec53919-034b-4f0e-b415-1bc1de9b0916@nvidia.com>
Date: Mon, 11 Nov 2024 15:21:36 +0800
From: Joseph Jang <jjang@...dia.com>
To: Bjorn Helgaas <helgaas@...nel.org>
Cc: shuah@...nel.org, tglx@...utronix.de, mochs@...dia.com,
 linux-kernel@...r.kernel.org, linux-kselftest@...r.kernel.org,
 linux-tegra@...r.kernel.org
Subject: Re: [PATCH] selftest: drivers: Add support to check duplicate hwirq



On 2024/10/19 3:34 AM, Bjorn Helgaas wrote:
> On Tue, Sep 03, 2024 at 06:44:26PM -0700, Joseph Jang wrote:
>> Validate there are no duplicate hwirq from the irq debug
>> file system /sys/kernel/debug/irq/irqs/* per chip name.
>>
>> One example log show 2 duplicated hwirq in the irq debug
>> file system.
>>
>> $ sudo cat /sys/kernel/debug/irq/irqs/163
>> handler:  handle_fasteoi_irq
>> device:   0019:00:00.0
>>       <SNIP>
>> node:     1
>> affinity: 72-143
>> effectiv: 76
>> domain:  irqchip@...000100022040000-3
>>   hwirq:   0xc8000000
>>   chip:    ITS-MSI
>>    flags:   0x20
>>
>> $ sudo cat /sys/kernel/debug/irq/irqs/174
>> handler:  handle_fasteoi_irq
>> device:   0039:00:00.0
>>      <SNIP>
>> node:     3
>> affinity: 216-287
>> effectiv: 221
>> domain:  irqchip@...000300022040000-3
>>   hwirq:   0xc8000000
>>   chip:    ITS-MSI
>>    flags:   0x20
>>
>> The irq-check.sh can help to collect hwirq and chip name from
>> /sys/kernel/debug/irq/irqs/* and print error log when find duplicate
>> hwirq per chip name.
>>
>> Kernel patch ("PCI/MSI: Fix MSI hwirq truncation") [1] fix above issue.
>> [1]: https://lore.kernel.org/all/20240115135649.708536-1-vidyas@nvidia.com/
> 
> I don't know enough about this issue to understand the details.  It
> seems like you look for duplicate hwirqs in chips with the same name,
> e.g., "ITS-MSI" in this case?  That name seems too generic to me
> (might there be several instances of "ITS-MSI" in a system?)
> 

As I know, each PCIe device typically has only one ITS-MSI controller.
Having multiple ITS-MSI instances for the same device would lead to 
confusion and potential conflicts in interrupt routing.

> Also, the name may come from chip->irq_print_chip(), so it apparently
> relies on irqchip drivers to make the names unique if there are
> multiple instances?
> 
> I would have expected looking for duplicates inside something more
> specific, like "irqchip@...000300022040000-3".  But again, I don't
> know enough about the problem to speak confidently here.
>

In our case, If we look for duplicates by different irq domains like
"irqchip@...000100022040000-3" and "irqchip@...000300022040000-3" as 
following example.

     $ sudo cat /sys/kernel/debug/irq/irqs/163
     handler:  handle_fasteoi_irq
     device:   0019:00:00.0
          <SNIP>
     node:     1
     affinity: 72-143
     effectiv: 76
     domain:  irqchip@...000100022040000-3
      hwirq:   0xc8000000
      chip:    ITS-MSI
       flags:   0x20
     $ sudo cat /sys/kernel/debug/irq/irqs/174
     handler:  handle_fasteoi_irq
     device:   0039:00:00.0
         <SNIP>
     node:     3
     affinity: 216-287
     effectiv: 221
     domain:  irqchip@...000300022040000-3
      hwirq:   0xc8000000
      chip:    ITS-MSI
       flags:   0x20

We could not detect the duplicated hwirq number (0xc8000000) in this case.


> Cosmetic nits:
> 
>    - Tweak subject to match history (use "git log --oneline
>      tools/testing/selftests/drivers/" to see it), e.g.,
> 
>        selftests: irq: Add check for duplicate hwirq
> 
>    - Rewrap commit log to fill 75 columns.  No point in using shorter
>      lines.
> 
>    - Indent the "$ sudu cat ..." block by a couple spaces since it's
>      effectively a quotation, not part of the main text body.
> 
>    - Possibly include sample output of irq-check.sh (also indented as a
>      quote) when run on the system where you manually found the
>      duplicate via "sudo cat /sys/kernel/debug/irq/irqs/..."
> 
>    - Reword "The irq-check.sh can help ..." to something like this:
> 
>        Add an irq-check.sh test to report errors when there are
>        duplicate hwirqs per chip name.
> 
>    - Since the kernel patch has already been merged, cite it like this
>      instead of using the https://lore URL:
> 
>        db744ddd59be ("PCI/MSI: Prevent MSI hardware interrupt number truncation")
> 

If you agree to use irq chip name ("ITS-MSI") to scan duplicate hwirq, I
could send version 2 patch to fix above suggestions.


Thank you,
Joseph.

>> Signed-off-by: Joseph Jang <jjang@...dia.com>
>> Reviewed-by: Matthew R. Ochs <mochs@...dia.com>
>> ---
>>   tools/testing/selftests/drivers/irq/Makefile  |  5 +++
>>   tools/testing/selftests/drivers/irq/config    |  2 +
>>   .../selftests/drivers/irq/irq-check.sh        | 39 +++++++++++++++++++
>>   3 files changed, 46 insertions(+)
>>   create mode 100644 tools/testing/selftests/drivers/irq/Makefile
>>   create mode 100644 tools/testing/selftests/drivers/irq/config
>>   create mode 100755 tools/testing/selftests/drivers/irq/irq-check.sh
>>
>> diff --git a/tools/testing/selftests/drivers/irq/Makefile b/tools/testing/selftests/drivers/irq/Makefile
>> new file mode 100644
>> index 000000000000..d6998017c861
>> --- /dev/null
>> +++ b/tools/testing/selftests/drivers/irq/Makefile
>> @@ -0,0 +1,5 @@
>> +# SPDX-License-Identifier: GPL-2.0
>> +
>> +TEST_PROGS := irq-check.sh
>> +
>> +include ../../lib.mk
>> diff --git a/tools/testing/selftests/drivers/irq/config b/tools/testing/selftests/drivers/irq/config
>> new file mode 100644
>> index 000000000000..a53d3b713728
>> --- /dev/null
>> +++ b/tools/testing/selftests/drivers/irq/config
>> @@ -0,0 +1,2 @@
>> +CONFIG_GENERIC_IRQ_DEBUGFS=y
>> +CONFIG_GENERIC_IRQ_INJECTION=y
>> diff --git a/tools/testing/selftests/drivers/irq/irq-check.sh b/tools/testing/selftests/drivers/irq/irq-check.sh
>> new file mode 100755
>> index 000000000000..e784777043a1
>> --- /dev/null
>> +++ b/tools/testing/selftests/drivers/irq/irq-check.sh
>> @@ -0,0 +1,39 @@
>> +#!/bin/bash
>> +# SPDX-License-Identifier: GPL-2.0
>> +
>> +# This script need root permission
>> +uid=$(id -u)
>> +if [ $uid -ne 0 ]; then
>> +	echo "SKIP: Must be run as root"
>> +	exit 4
>> +fi
>> +
>> +# Ensure debugfs is mounted
>> +mount -t debugfs nodev /sys/kernel/debug 2>/dev/null
>> +if [ ! -d "/sys/kernel/debug/irq/irqs" ]; then
>> +	echo "SKIP: irq debugfs not found"
>> +	exit 4
>> +fi
>> +
>> +# Traverse the irq debug file system directory to collect chip_name and hwirq
>> +hwirq_list=$(for irq_file in /sys/kernel/debug/irq/irqs/*; do
>> +	# Read chip name and hwirq from the irq_file
>> +	chip_name=$(cat "$irq_file" | grep -m 1 'chip:' | awk '{print $2}')
>> +	hwirq=$(cat "$irq_file" | grep -m 1 'hwirq:' | awk '{print $2}' )
>> +
>> +	if [ -z "$chip_name" ] || [ -z "$hwirq" ]; then
>> +		continue
>> +	fi
>> +
>> +	echo "$chip_name $hwirq"
>> +done)
>> +
>> +dup_hwirq_list=$(echo "$hwirq_list" | sort | uniq -cd)
>> +
>> +if [ -n "$dup_hwirq_list" ]; then
>> +	echo "ERROR: Found duplicate hwirq"
>> +	echo "$dup_hwirq_list"
>> +	exit 1
>> +fi
>> +
>> +exit 0
>> -- 
>> 2.34.1
>>
>