linux-kernel - Re: [PATCH] genirq/msi: Add the address and data that show MSI/MSIX

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Message-ID: <f6e44f34-8800-421c-ba2c-755c10a6840e@163.com>
Date: Fri, 28 Feb 2025 00:49:38 +0800
From: Hans Zhang <18255117159@....com>
To: Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
Cc: tglx@...utronix.de, kw@...ux.com, kwilczynski@...nel.org,
 bhelgaas@...gle.com, cassel@...nel.org, linux-pci@...r.kernel.org,
 linux-kernel@...r.kernel.org
Subject: Re: [PATCH] genirq/msi: Add the address and data that show MSI/MSIX



On 2025/2/28 00:39, Manivannan Sadhasivam wrote:
> On Fri, Feb 28, 2025 at 12:28:21AM +0800, Hans Zhang wrote:
>> Add to view the addresses and data stored in the MSI capability or the
>> addresses and data stored in the MSIX vector table.
>>
>> e.g.
>> root@...t:/sys/bus/pci/devices/<dev>/msi_irqs# ls
>> 86  87  88  89
>> root@...t:/sys/bus/pci/devices/<dev>/msi_irqs# cat *
>> msix
>>   address_hi: 0x00000000
>>   address_lo: 0x0e060040
>>   msg_data: 0x00000000
>> msix
>>   address_hi: 0x00000000
>>   address_lo: 0x0e060040
>>   msg_data: 0x00000001
>> msix
>>   address_hi: 0x00000000
>>   address_lo: 0x0e060040
>>   msg_data: 0x00000002
>> msix
>>   address_hi: 0x00000000
>>   address_lo: 0x0e060040
>>   msg_data: 0x00000003
>>
>> Signed-off-by: Hans Zhang <18255117159@....com>
>> ---
>>   kernel/irq/msi.c | 12 +++++++++++-
>>   1 file changed, 11 insertions(+), 1 deletion(-)
>>
>> diff --git a/kernel/irq/msi.c b/kernel/irq/msi.c
>> index 396a067a8a56..a37a3e535fb8 100644
>> --- a/kernel/irq/msi.c
>> +++ b/kernel/irq/msi.c
>> @@ -503,8 +503,18 @@ static ssize_t msi_mode_show(struct device *dev, struct device_attribute *attr,
>>   {
>>   	/* MSI vs. MSIX is per device not per interrupt */
>>   	bool is_msix = dev_is_pci(dev) ? to_pci_dev(dev)->msix_enabled : false;
>> +	struct msi_desc *desc;
>> +	u32 irq;
>> +
>> +	if (kstrtoint(attr->attr.name, 10, &irq) < 0)
>> +		return 0;
>>   
>> -	return sysfs_emit(buf, "%s\n", is_msix ? "msix" : "msi");
>> +	desc = irq_get_msi_desc(irq);
>> +	return sysfs_emit(
>> +		buf,
>> +		"%s\n address_hi: 0x%08x\n address_lo: 0x%08x\n msg_data: 0x%08x\n",
>> +		is_msix ? "msix" : "msi", desc->msg.address_hi,
>> +		desc->msg.address_lo, desc->msg.data);
> 
> Sysfs is an ABI. You cannot change the semantics of an attribute.
> 

Thanks Mani for the tip.

If I want to implement similar functionality, where should I add it? 
Since this sysfs node is the only one that displays the MSI/MSIX 
interrupt number, I don't know where to implement similar debug 
functionality at this time. Do you have any suggestions? Or it shouldn't 
have a similar function.

Best regards
Hans