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

[Vasant Hegde <vasant.hegde@amd.com>]

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@amd.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/


-Vasant