[PATCH v3 6/8] iommu/amd: Add debugfs support to dump device table

Dheeraj Kumar Srivastava
2025-02-06T06:02:44Z

IOMMU uses device table data structure to get per-device information for
DMA remapping, interrupt remapping, and other functionalities. It's a
valuable data structure to visualize for debugging issues related to
IOMMU.

eg.
To dump device table entry for a particular device
#echo 0000:c4:00.0 > /sys/kernel/debug/iommu/amd/devid
#cat /sys/kernel/debug/iommu/amd/devtbl

or
#echo c4:00.0 > /sys/kernel/debug/iommu/amd/devid
#cat /sys/kernel/debug/iommu/amd/devtbl

Signed-off-by: Dheeraj Kumar Srivastava <dheerajkumar.srivastava@amd.com>
---
drivers/iommu/amd/debugfs.c | 49 +++++++++++++++++++++++++++++++++++++
1 file changed, 49 insertions(+)

diff --git a/drivers/iommu/amd/debugfs.c b/drivers/iommu/amd/debugfs.c
index f292b93f9318..1377795814d1 100644
--- a/drivers/iommu/amd/debugfs.c
+++ b/drivers/iommu/amd/debugfs.c
@@ -203,6 +203,53 @@ static int devid_show(struct seq_file *m, void *unused)
}
DEFINE_SHOW_STORE_ATTRIBUTE(devid);

+static void dump_dte(struct seq_file *m, struct amd_iommu_pci_seg *pci_seg, u16 devid)
+{
+ struct dev_table_entry *dev_table;
+ struct amd_iommu *iommu;
+
+ 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;
+ }
+
+ seq_printf(m, "%-12s %16s %16s %16s %16s iommu\n", "DeviceId",
+ "QWORD[3]", "QWORD[2]", "QWORD[1]", "QWORD[0]");
+ seq_printf(m, "%04x:%02x:%02x:%x ", pci_seg->id, PCI_BUS_NUM(devid),
+ PCI_SLOT(devid), PCI_FUNC(devid));
+ for (int i = 3; i >= 0; --i)
+ seq_printf(m, "%016llx ", dev_table[devid].data[i]);
+ seq_printf(m, "iommu%d\n", iommu->index);
+}
+
+static int iommu_devtbl_show(struct seq_file *m, void *unused)
+{
+ struct amd_iommu_pci_seg *pci_seg;
+ u16 seg, devid;
+
+ 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_dte(m, pci_seg, devid);
+ break;
+ }
+
+ return 0;
+}
+DEFINE_SHOW_ATTRIBUTE(iommu_devtbl);
+
void amd_iommu_debugfs_setup(void)
{
struct amd_iommu *iommu;
@@ -223,4 +270,6 @@ void amd_iommu_debugfs_setup(void)
}
debugfs_create_file("devid", 0644, amd_iommu_debugfs, NULL,
&devid_fops);
+ debugfs_create_file("devtbl", 0444, amd_iommu_debugfs, NULL,
+ &iommu_devtbl_fops);
}
--
2.25.1