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iommu/amd: Add debugfs support to dump device table

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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>
Reviewed-by: Vasant Hegde <vasant.hegde@amd.com>
Link: https://lore.kernel.org/r/20250702093804.849-7-dheerajkumar.srivastava@amd.com
Signed-off-by: Will Deacon <will@kernel.org>
This commit is contained in:
Dheeraj Kumar Srivastava
2025-07-02 15:08:02 +05:30
committed by Will Deacon
parent 2e98940f12
commit b484577824
1 changed files with 49 additions and 0 deletions
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49
drivers/iommu/amd/debugfs.c
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@@ -208,6 +208,53 @@ 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, "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_dte(m, pci_seg, devid);
break;
}
return 0;
}
DEFINE_SHOW_ATTRIBUTE(iommu_devtbl);
void amd_iommu_debugfs_setup(void)
{
struct amd_iommu *iommu;
@@ -232,4 +279,6 @@ 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);
}