linux-kernel - Re: [PATCH v5 7/8] iommu/amd: Add debugfs support to dump IRT Table

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Message-ID: <58921dc3-aa6e-41bc-90d3-d25a4a2cce8b@amd.com>
Date: Wed, 4 Jun 2025 21:46:16 +0530
From: Dheeraj Kumar Srivastava <dheerajkumar.srivastava@....com>
To: Vasant Hegde <vasant.hegde@....com>, joro@...tes.org,
 suravee.suthikulpanit@....com, will@...nel.org, robin.murphy@....com,
 linux-kernel@...r.kernel.org, iommu@...ts.linux.dev
Subject: Re: [PATCH v5 7/8] iommu/amd: Add debugfs support to dump IRT Table

Hi Vasant,

Thanks for reviewing the patch.

On 5/1/2025 3:36 PM, Vasant Hegde wrote:
> 
> 
> On 4/7/2025 11:04 PM, Dheeraj Kumar Srivastava wrote:
>> In cases where we have an issue in the device interrupt path with IOMMU
>> interrupt remapping enabled, dumping valid IRT table entries for the device
>> is very useful and good input for debugging the issue.
>>
>> eg.
>> -> To dump irte entries for a particular device
>>     #echo "c4:00.0" > /sys/kernel/debug/iommu/amd/devid
>>     #cat /sys/kernel/debug/iommu/amd/irqtbl | less
>>
>>     or
>>
>>     #echo "0000:c4:00.0" > /sys/kernel/debug/iommu/amd/devid
>>     #cat /sys/kernel/debug/iommu/amd/irqtbl | less
>>
>> Signed-off-by: Dheeraj Kumar Srivastava <dheerajkumar.srivastava@....com>
>> ---
>>   drivers/iommu/amd/debugfs.c | 106 ++++++++++++++++++++++++++++++++++++
>>   1 file changed, 106 insertions(+)
>>
>> diff --git a/drivers/iommu/amd/debugfs.c b/drivers/iommu/amd/debugfs.c
>> index c6ff47561afb..28fe546e0bc0 100644
>> --- a/drivers/iommu/amd/debugfs.c
>> +++ b/drivers/iommu/amd/debugfs.c
>> @@ -11,6 +11,7 @@
>>   #include <linux/pci.h>
>>   
>>   #include "amd_iommu.h"
>> +#include "../irq_remapping.h"
>>   
>>   static struct dentry *amd_iommu_debugfs;
>>   
>> @@ -254,6 +255,109 @@ static int iommu_devtbl_show(struct seq_file *m, void *unused)
>>   }
>>   DEFINE_SHOW_ATTRIBUTE(iommu_devtbl);
>>   
>> +static void dump_128_irte(struct seq_file *m, struct irq_remap_table *table, u16 int_tab_len)
>> +{
>> +	struct irte_ga *ptr, *irte;
>> +	int index;
>> +
>> +	for (index = 0; index < int_tab_len; index++) {
>> +		ptr = (struct irte_ga *)table->table;
>> +		irte = &ptr[index];
>> +
>> +		if (AMD_IOMMU_GUEST_IR_VAPIC(amd_iommu_guest_ir) &&
>> +		    !irte->lo.fields_vapic.valid)
>> +			continue;
>> +		else if (!irte->lo.fields_remap.valid)
>> +			continue;
>> +		seq_printf(m, "IRT[%04d] %016llx %016llx\n", index, irte->hi.val, irte->lo.val);
>> +	}
>> +}
>> +
>> +static void dump_32_irte(struct seq_file *m, struct irq_remap_table *table, u16 int_tab_len)
>> +{
>> +	union irte *ptr, *irte;
>> +	int index;
>> +
>> +	for (index = 0; index < int_tab_len; index++) {
>> +		ptr = (union irte *)table->table;
>> +		irte = &ptr[index];
>> +
>> +		if (!irte->fields.valid)
>> +			continue;
>> +		seq_printf(m, "IRT[%04d] %08x\n", index, irte->val);
>> +	}
>> +}
>> +
>> +static void dump_irte(struct seq_file *m, u16 devid, struct amd_iommu_pci_seg *pci_seg)
>> +{
>> +	struct dev_table_entry *dev_table;
>> +	struct irq_remap_table *table;
>> +	struct amd_iommu *iommu;
>> +	unsigned long flags;
>> +	u16 int_tab_len;
>> +
>> +	table = pci_seg->irq_lookup_table[devid];
>> +	if (!table) {
>> +		seq_printf(m, "IRQ lookup table not set for %04x:%02x:%02x:%x\n",
>> +			   pci_seg->id, PCI_BUS_NUM(devid), PCI_SLOT(devid), PCI_FUNC(devid));
>> +		return;
>> +	}
>> +
>> +	iommu = pci_seg->rlookup_table[devid];
>> +	if (!iommu)
>> +		return;
>> +
>> +	dev_table = get_dev_table(iommu);
>> +	if (!dev_table) {
>> +		seq_puts(m, "Device table not found");
>> +		return;
>> +	}
>> +
>> +	int_tab_len = 1 << ((dev_table[devid].data[2] >> 1) & 0xfULL);
> 
> This is hard to read. Please use the macros like FIELD_GET
> 
>> +	if (int_tab_len > 2048)
> 
> s/2048/MAX_IRQS_PER_TABLE_2K/

Sure I will use macros to fetch and validate IRT table length from DTE.

Thanks
Dheeraj

> 
> 
> -Vasant
> 
>