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Subject: [PATCH v2 5/5] iommu/amd - Add a debugfs entry to specify a IOMMU
 device table entry
From:   Gary R Hook <gary.hook@amd.com>
To:     iommu@lists.linux-foundation.org
Cc:     joro@8bytes.org, linux-kernel@vger.kernel.org
Date:   Thu, 08 Mar 2018 18:51:31 -0600
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Initially (at boot) the device table values dumped are all of the
active devices.  Add a devid debugfs file to allow the user to select a
single device table entry to dump (active or not). Let any devid value
greater than the maximum allowable PCI ID (0xFFFF) restore the
behavior to that effective at boot.

Signed-off-by: Gary R Hook <gary.hook@amd.com>
---
 drivers/iommu/amd_iommu_debugfs.c |  109 ++++++++++++++++++++++++++++++++++---
 1 file changed, 100 insertions(+), 9 deletions(-)

diff --git a/drivers/iommu/amd_iommu_debugfs.c b/drivers/iommu/amd_iommu_debugfs.c
index c4e071f7a5b9..aa6935340163 100644
--- a/drivers/iommu/amd_iommu_debugfs.c
+++ b/drivers/iommu/amd_iommu_debugfs.c
@@ -28,6 +28,7 @@ static DEFINE_RWLOCK(iommu_debugfs_lock);
 #define	MAX_NAME_LEN	20
 
 static unsigned int amd_iommu_verbose = 0;
+static unsigned int amd_iommu_devid = ~0;
 
 static unsigned int amd_iommu_count_valid_dtes(int start, int end)
 {
@@ -81,6 +82,76 @@ static const struct file_operations amd_iommu_debugfs_dtecount_ops = {
 	.write = NULL,
 };
 
+static ssize_t amd_iommu_debugfs_devid_read(struct file *filp,
+					    char __user *ubuf,
+					    size_t count, loff_t *offp)
+{
+	struct amd_iommu *iommu = filp->private_data;
+	unsigned int obuflen = 512;
+	unsigned int oboff = 0;
+	ssize_t ret;
+	char *obuf;
+
+	if (!iommu)
+		return 0;
+
+	obuf = kmalloc(OBUFLEN, GFP_KERNEL);
+	if (!obuf)
+		return -ENOMEM;
+
+	if (amd_iommu_verbose)
+		oboff += OSCNPRINTF("%02x:%02x:%x (%u / %04x)\n",
+				    PCI_BUS_NUM(amd_iommu_devid),
+				    PCI_SLOT(amd_iommu_devid),
+				    PCI_FUNC(amd_iommu_devid),
+				    amd_iommu_devid, amd_iommu_devid);
+	else
+		oboff += OSCNPRINTF("%u\n", amd_iommu_devid);
+
+	ret = simple_read_from_buffer(ubuf, count, offp, obuf, oboff);
+	kfree(obuf);
+
+	return ret;
+}
+
+static ssize_t amd_iommu_debugfs_devid_write(struct file *filp,
+					    const char __user *ubuf,
+					    size_t count, loff_t *offp)
+{
+	unsigned int pci_id, pci_slot, pci_func;
+	unsigned int obuflen = 80;
+	ssize_t ret;
+	char *obuf;
+	int n;
+
+	obuf = kmalloc(OBUFLEN, GFP_KERNEL);
+	if (!obuf)
+		return -ENOMEM;
+
+	ret = simple_write_to_buffer(obuf, OBUFLEN, offp, ubuf, count);
+
+	if (strnchr(obuf, OBUFLEN, ':'))
+	{
+		n = sscanf(obuf, "%x:%x.%x", &pci_id, &pci_slot, &pci_func);
+		if (n == 3)
+			amd_iommu_devid = PCI_DEVID(pci_id, PCI_DEVFN(pci_slot, pci_func));
+	} else if (obuf[0] == '0' && obuf[1] == 'x') {
+		n = sscanf(obuf, "%x", &amd_iommu_devid);
+	} else {
+		n = sscanf(obuf, "%d", &amd_iommu_devid);
+	}
+	kfree(obuf);
+
+	return ret;
+}
+
+static const struct file_operations amd_iommu_debugfs_devid_ops = {
+	.owner = THIS_MODULE,
+	.open = simple_open,
+	.read = amd_iommu_debugfs_devid_read,
+	.write = amd_iommu_debugfs_devid_write,
+};
+
 #define	MAX_PCI_ID	0xFFFF
 
 #define	PRINTDTE(i)	OSCNPRINTF("%02x:%02x:%x - %016llx %016llx %016llx %016llx\n", \
@@ -106,19 +177,28 @@ static ssize_t amd_iommu_debugfs_dte_read(struct file *filp,
 		return 0;
 
 	/* Count the number of valid entries in the device table */
-	istart = 0;
-	iend = MAX_PCI_ID;
-	n = amd_iommu_count_valid_dtes(istart, iend);
+	if (amd_iommu_devid > MAX_PCI_ID) {
+		istart = 0;
+		iend = MAX_PCI_ID;
+		n = amd_iommu_count_valid_dtes(istart, iend);
+	} else {
+		n = 1;
+	}
 	obuflen = n * 80;
 
 	obuf = kmalloc(OBUFLEN, GFP_KERNEL);
 	if (!obuf)
 		return -ENOMEM;
 
-	for (i = istart ; i <= iend ; i++)
-		if ((amd_iommu_dev_table[i].data[0] ^ 0x3)
-		     || amd_iommu_dev_table[i].data[1])
-			oboff += PRINTDTE(i);
+	if (amd_iommu_devid > MAX_PCI_ID) {
+		for (i = istart ; i <= iend ; i++)
+			if ((amd_iommu_dev_table[i].data[0] ^ 0x3)
+			     || amd_iommu_dev_table[i].data[1])
+				oboff += PRINTDTE(i);
+	} else {
+		i = amd_iommu_devid;
+		oboff += PRINTDTE(i);
+	}
 
 	ret = simple_read_from_buffer(ubuf, count, offp, obuf, oboff);
 	kfree(obuf);
@@ -135,12 +215,17 @@ static const struct file_operations amd_iommu_debugfs_dte_ops = {
 
 static char readmetext[] =
 "devicetable             Print active entries in the device table\n"
+"devid                   Controls which device IDs are printed\n"
 "count                   Count of active devices\n"
 "verbose                 Provide additional descriptive text\n"
 "\n"
 "                        Dumping the Device Table\n"
-"The device table is scanned for entries that appear to be active. The\n"
-"default range is from 0 to 0xFFFF, and only active entries will be reported\n"
+"The device table is scanned for entries that appear to be active.\n"
+"The default (initial) range is from 0 to 0xFFFF, represented by a devid\n"
+"value greater than 0xFFFF, and only active entries will be reported.\n"
+"If devid is set to a specific value, only that device entry will be\n"
+"displayed (active or not). devid may be specified as ##:##:#, a decimal\n"
+"value, or a hex value.\n"
 "\n";
 
 static ssize_t amd_iommu_debugfs_readme_read(struct file *filp,
@@ -204,6 +289,12 @@ void amd_iommu_debugfs_setup(struct amd_iommu *iommu)
 	if (!d_dte)
 		goto err;
 
+	d_dte = debugfs_create_file("devid", 0400,
+				    iommu->debugfs_instance, iommu,
+				    &amd_iommu_debugfs_devid_ops);
+	if (!d_dte)
+		goto err;
+
 	d_dte = debugfs_create_file("README", 0400,
 				    iommu->debugfs_instance, iommu,
 				    &amd_iommu_debugfs_readme_ops);