iommu/amd: Add debugfs support to dump IRT Table

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>
Reviewed-by: Vasant Hegde <vasant.hegde@amd.com>
Link: https://lore.kernel.org/r/20250702093804.849-8-dheerajkumar.srivastava@amd.com
Signed-off-by: Will Deacon <will@kernel.org>

1 files changed, 108 insertions, 0 deletions

diff --git a/drivers/iommu/amd/debugfs.c b/drivers/iommu/amd/debugfs.c
index b01eea2fbe03..10fa217a7119 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;
 
@@ -255,6 +256,111 @@ 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, "Enter a valid device ID to 'devid' file\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;
@@ -281,4 +387,6 @@ 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);
 }