[PATCH v3 7/8] iommu/amd: Add debugfs support to dump IRT Table

Dheeraj Kumar Srivastava
2025-02-06T06:02:59Z

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 | 89 +++++++++++++++++++++++++++++++++++++
1 file changed, 89 insertions(+)

diff --git a/drivers/iommu/amd/debugfs.c b/drivers/iommu/amd/debugfs.c
index 1377795814d1..0aff1d616108 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;

@@ -250,6 +251,92 @@ 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)
+{
+ struct irte_ga *ptr, *irte;
+ int index;
+
+ for (index = 0; index < MAX_IRQS_PER_TABLE; 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)
+{
+ union irte *ptr, *irte;
+ int index;
+
+ for (index = 0; index < MAX_IRQS_PER_TABLE; 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 irq_remap_table *table;
+ unsigned long flags;
+
+ 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;
+ }
+
+ 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);
+ else
+ dump_32_irte(m, table);
+ 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");
+ return 0;
+ }
+
+ seg = PCI_SBDF_TO_SEGID(sbdf);
+ devid = PCI_SBDF_TO_DEVID(sbdf);
+
+ for_each_pci_segment(pci_seg) {
+ if (pci_seg->id != seg)
+ continue;
+ dump_irte(m, devid, pci_seg);
+ break;
+ }
+
+ return 0;
+}
+DEFINE_SHOW_ATTRIBUTE(iommu_irqtbl);
+
void amd_iommu_debugfs_setup(void)
{
struct amd_iommu *iommu;
@@ -272,4 +359,6 @@ void amd_iommu_debugfs_setup(void)
&devid_fops);
debugfs_create_file("devtbl", 0444, amd_iommu_debugfs, NULL,
&iommu_devtbl_fops);
+ debugfs_create_file("irqtbl", 0444, amd_iommu_debugfs, NULL,
+ &iommu_irqtbl_fops);
}
--
2.25.1