iommu/amd: Add support for device id user input

Dumping IOMMU data structures like device table, IRT, etc., for all devices
on the system will be a lot of data dumped in a file. Also, user may want
to dump and analyze these data structures just for one or few devices. So
dumping IOMMU data structures like device table, IRT etc for all devices
is not a good approach.

Add "device id" user input to be used for dumping IOMMU data structures
like device table, IRT etc in AMD IOMMU debugfs.

eg.
1. # echo 0000:01:00.0 > /sys/kernel/debug/iommu/amd/devid
   # cat /sys/kernel/debug/iommu/amd/devid
   Output : 0000:01:00.0

2. # echo 01:00.0 > /sys/kernel/debug/iommu/amd/devid
   # cat /sys/kernel/debug/iommu/amd/devid
   Output : 0000:01:00.0

Signed-off-by: Dheeraj Kumar Srivastava <[email protected]>
Reviewed-by: Vasant Hegde <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Will Deacon <[email protected]>

Author: dhsrivas

drivers/iommu/amd/debugfs.c

@@ -16,6 +16,9 @@ static struct dentry *amd_iommu_debugfs;
 
 #define	MAX_NAME_LEN	20
 #define	OFS_IN_SZ	8
+#define	DEVID_IN_SZ	16
+
+static int sbdf = -1;
 
 static ssize_t iommu_mmio_write(struct file *filp, const char __user *ubuf,
 				size_t cnt, loff_t *ppos)
@@ -131,6 +134,80 @@ static int iommu_cmdbuf_show(struct seq_file *m, void *unused)
 }
 DEFINE_SHOW_ATTRIBUTE(iommu_cmdbuf);
 
+static ssize_t devid_write(struct file *filp, const char __user *ubuf,
+			   size_t cnt, loff_t *ppos)
+{
+	struct amd_iommu_pci_seg *pci_seg;
+	int seg, bus, slot, func;
+	struct amd_iommu *iommu;
+	char *srcid_ptr;
+	u16 devid;
+	int i;
+
+	sbdf = -1;
+
+	if (cnt >= DEVID_IN_SZ)
+		return -EINVAL;
+
+	srcid_ptr = memdup_user_nul(ubuf, cnt);
+	if (IS_ERR(srcid_ptr))
+		return PTR_ERR(srcid_ptr);
+
+	i = sscanf(srcid_ptr, "%x:%x:%x.%x", &seg, &bus, &slot, &func);
+	if (i != 4) {
+		i = sscanf(srcid_ptr, "%x:%x.%x", &bus, &slot, &func);
+		if (i != 3) {
+			kfree(srcid_ptr);
+			return -EINVAL;
+		}
+		seg = 0;
+	}
+
+	devid = PCI_DEVID(bus, PCI_DEVFN(slot, func));
+
+	/* Check if user device id input is a valid input */
+	for_each_pci_segment(pci_seg) {
+		if (pci_seg->id != seg)
+			continue;
+		if (devid > pci_seg->last_bdf) {
+			kfree(srcid_ptr);
+			return -EINVAL;
+		}
+		iommu = pci_seg->rlookup_table[devid];
+		if (!iommu) {
+			kfree(srcid_ptr);
+			return -ENODEV;
+		}
+		break;
+	}
+
+	if (pci_seg->id != seg) {
+		kfree(srcid_ptr);
+		return -EINVAL;
+	}
+
+	sbdf = PCI_SEG_DEVID_TO_SBDF(seg, devid);
+
+	kfree(srcid_ptr);
+
+	return cnt;
+}
+
+static int devid_show(struct seq_file *m, void *unused)
+{
+	u16 devid;
+
+	if (sbdf >= 0) {
+		devid = PCI_SBDF_TO_DEVID(sbdf);
+		seq_printf(m, "%04x:%02x:%02x.%x\n", PCI_SBDF_TO_SEGID(sbdf),
+			   PCI_BUS_NUM(devid), PCI_SLOT(devid), PCI_FUNC(devid));
+	} else
+		seq_puts(m, "No or Invalid input provided\n");
+
+	return 0;
+}
+DEFINE_SHOW_STORE_ATTRIBUTE(devid);
+
 void amd_iommu_debugfs_setup(void)
 {
 	struct amd_iommu *iommu;
@@ -152,4 +229,7 @@ void amd_iommu_debugfs_setup(void)
 		debugfs_create_file("cmdbuf", 0444, iommu->debugfs, iommu,
 				    &iommu_cmdbuf_fops);
 	}
+
+	debugfs_create_file("devid", 0644, amd_iommu_debugfs, NULL,
+			    &devid_fops);
 }