Re: [PATCH v6 7/8] iommu/amd: Add debugfs support to dump IRT Table

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

Dheeraj,


On 6/4/2025 10:06 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 | 108 ++++++++++++++++++++++++++++++++++++
>  1 file changed, 108 insertions(+)
> 
> diff --git a/drivers/iommu/amd/debugfs.c b/drivers/iommu/amd/debugfs.c
> index 38d3cab5fd8d..7a056ebcc7c3 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 +255,111 @@ 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 = dev_table[devid].data[2] & DTE_INTTABLEN_MASK;
> +	if (int_tab_len != DTE_INTTABLEN_512 && int_tab_len != DTE_INTTABLEN_2K) {
> +		seq_puts(m, "The device's DTE contains an invalid IRT length value.");
> +		return;
> +	}
> +
> +	seq_printf(m, "DeviceId %04x:%02x:%02x.%x\n", pci_seg->id, PCI_BUS_NUM(devid),
> +		   PCI_SLOT(devid), PCI_FUNC(devid));
> +
> +	raw_spin_lock_irqsave(&table->lock, flags);
> +	if (AMD_IOMMU_GUEST_IR_GA(amd_iommu_guest_ir))
> +		dump_128_irte(m, table, BIT(int_tab_len >> 1));
> +	else
> +		dump_32_irte(m, table, BIT(int_tab_len >> 1));
> +	seq_puts(m, "\n");
> +	raw_spin_unlock_irqrestore(&table->lock, flags);
> +}
> +
> +static int iommu_irqtbl_show(struct seq_file *m, void *unused)
> +{
> +	struct amd_iommu_pci_seg *pci_seg;
> +	u16 devid, seg;
> +
> +	if (!irq_remapping_enabled) {
> +		seq_puts(m, "Interrupt remapping is disabled\n");
> +		return 0;
> +	}
> +
> +	if (sbdf < 0) {
> +		seq_puts(m, "Please provide valid device id input\n");

Again same as previous patch comment. Please add proper description so that user
know where to input devid.

-Vasant