linux-kernel - Re: [PATCH] arm64: smp: Fix missing IPI statistics

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Date: Thu, 20 Jun 2024 11:52:13 +0800
From: Jinjie Ruan <ruanjinjie@...wei.com>
To: Will Deacon <will@...nel.org>
CC: <catalin.marinas@....com>, <mark.rutland@....com>,
	<dianders@...omium.org>, <swboyd@...omium.org>, <sumit.garg@...aro.org>,
	<frederic@...nel.org>, <scott@...amperecomputing.com>,
	<misono.tomohiro@...itsu.com>, <linux-arm-kernel@...ts.infradead.org>,
	<linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] arm64: smp: Fix missing IPI statistics



On 2024/6/19 21:32, Will Deacon wrote:
> On Fri, Jun 07, 2024 at 03:47:16PM +0800, Jinjie Ruan wrote:
>> commit 83cfac95c018 ("genirq: Allow interrupts to be excluded from
>> /proc/interrupts") is to avoid IPIs appear twice in /proc/interrupts.
>> But the commit 331a1b3a836c ("arm64: smp: Add arch support for backtrace
>> using pseudo-NMI") and commit 2f5cd0c7ffde("arm64: kgdb: Implement
>> kgdb_roundup_cpus() to enable pseudo-NMI roundup") set CPU_BACKTRACE and
>> KGDB_ROUNDUP IPIs "IRQ_HIDDEN" flag but not show them in
>> arch_show_interrupts(), which cause the interrupt kstat_irqs accounting
>> is missing in display.
>>
>> Fixes: 331a1b3a836c ("arm64: smp: Add arch support for backtrace using pseudo-NMI")
>> Signed-off-by: Jinjie Ruan <ruanjinjie@...wei.com>
>> ---
>>  arch/arm64/kernel/smp.c | 3 ++-
>>  1 file changed, 2 insertions(+), 1 deletion(-)
>>
>> diff --git a/arch/arm64/kernel/smp.c b/arch/arm64/kernel/smp.c
>> index 31c8b3094dd7..7f9a5cf0f3b8 100644
>> --- a/arch/arm64/kernel/smp.c
>> +++ b/arch/arm64/kernel/smp.c
>> @@ -1039,7 +1039,8 @@ void __init set_smp_ipi_range(int ipi_base, int n)
>>  		}
>>  
>>  		ipi_desc[i] = irq_to_desc(ipi_base + i);
>> -		irq_set_status_flags(ipi_base + i, IRQ_HIDDEN);
>> +		if (i < NR_IPI)
>> +			irq_set_status_flags(ipi_base + i, IRQ_HIDDEN);
>>  	}
> 
> Please can you show the contents of /proc/interrupts before and after
> this patch and put that in the commit message? I'm not seeing how the
> two new IPIs get picked up by arch_show_interrupts().


Before this patch, CPU_BACKTRACE and KGDB_ROUNDUP IPIs are missing as below:

/ # cat /proc/interrupts
           CPU0       CPU1       CPU2       CPU3
 11:        463        656        243        654     GICv3  27 Level
arch_timer
 13:         14          0          0          0     GICv3  33 Level
uart-pl011
 17:          0          0          0          0   ITS-MSI 16384 Edge
  virtio2-config
 18:          0          5          0          0   ITS-MSI 16385 Edge
  virtio2-input
 19:         68          0          0          0     GICv3  78 Edge
virtio0
 20:          0          0          0          0     GICv3  79 Edge
virtio1
 21:          0          0          0          0     GICv3  34 Level
rtc-pl031
 22:          2          2          2          2     GICv3  23 Level
arm-pmu
 23:          0          0          0          0   ITS-MSI 32768 Edge
  virtio3-config
 24:          0          0          0          0   ITS-MSI 32769 Edge
  virtio3-requests
 25:          0          0          0          0 9030000.pl061   3 Edge
    GPIO Key Poweroff
IPI0:        15         13          5         21       Rescheduling
interrupts
IPI1:       385        129        282        194       Function call
interrupts
IPI2:         0          0          0          0       CPU stop interrupts
IPI3:         0          0          0          0       CPU stop (for
crash dump) interrupts
IPI4:         0          0          0          0       Timer broadcast
interrupts
IPI5:         1          0          0          0       IRQ work interrupts
Err:          0


After this patch the hwirq6/7 IPI is also displayed:

/ # cat /proc/interrupts
           CPU0       CPU1       CPU2       CPU3
  7:          0          0          0          0     GICv3   6 Edge      IPI
  8:          0          0          0          0     GICv3   7 Edge      IPI
 11:        414        433        424        422     GICv3  27 Level
arch_timer
 13:         21          0          0          0     GICv3  33 Level
uart-pl011
 17:          0          0          0          0   ITS-MSI 16384 Edge
  virtio2-config
 18:          0          6          0          0   ITS-MSI 16385 Edge
  virtio2-input
 19:         60          0          0          0     GICv3  78 Edge
virtio0
 20:          0          0          0          0     GICv3  79 Edge
virtio1
 21:          0          0          0          0     GICv3  34 Level
rtc-pl031
 22:          3          3          3          3     GICv3  23 Level
arm-pmu
 23:          0          0          0          0   ITS-MSI 32768 Edge
  virtio3-config
 24:          0          0          0          0   ITS-MSI 32769 Edge
  virtio3-requests
 25:          0          0          0          0 9030000.pl061   3 Edge
    GPIO Key Poweroff
IPI0:        15         13         19         12       Rescheduling
interrupts
IPI1:       241        162        328        252       Function call
interrupts
IPI2:         0          0          0          0       CPU stop interrupts
IPI3:         0          0          0          0       CPU stop (for
crash dump) interrupts
IPI4:         0          0          0          0       Timer broadcast
interrupts
IPI5:         0          1          0          0       IRQ work interrupts
Err:          0


> 
> Thanks,
> 
> Will