drm/xe/pf: Improve reading VF config blob from debugfs

Due to the use of the file operation flows, we might encode the
VF config blob multiple times. Avoid that by capturing it once
during the open() operation instead of the read() operation.

Signed-off-by: Michal Wajdeczko <michal.wajdeczko@intel.com>
Reviewed-by: Piotr Piórkowski <piotr.piorkowski@intel.com>
Link: https://lore.kernel.org/r/20251004162036.1800-1-michal.wajdeczko@intel.com

1 files changed, 33 insertions, 11 deletions

diff --git a/drivers/gpu/drm/xe/xe_gt_sriov_pf_debugfs.c b/drivers/gpu/drm/xe/xe_gt_sriov_pf_debugfs.c
index 44fec2aae536..c026a3910e7e 100644
--- a/drivers/gpu/drm/xe/xe_gt_sriov_pf_debugfs.c
+++ b/drivers/gpu/drm/xe/xe_gt_sriov_pf_debugfs.c
@@ -436,15 +436,19 @@ static const struct file_operations guc_state_ops = {
  *                  :   ├── config_blob
  */
 
-static ssize_t config_blob_read(struct file *file, char __user *buf,
-				size_t count, loff_t *pos)
+struct config_blob_data {
+	size_t size;
+	u8 blob[];
+};
+
+static int config_blob_open(struct inode *inode, struct file *file)
 {
 	struct dentry *dent = file_dentry(file);
 	struct dentry *parent = dent->d_parent;
 	struct xe_gt *gt = extract_gt(parent);
 	unsigned int vfid = extract_vfid(parent);
+	struct config_blob_data *cbd;
 	ssize_t ret;
-	void *tmp;
 
 	ret = xe_gt_sriov_pf_config_save(gt, vfid, NULL, 0);
 	if (!ret)
@@ -452,16 +456,27 @@ static ssize_t config_blob_read(struct file *file, char __user *buf,
 	if (ret < 0)
 		return ret;
 
-	tmp = kzalloc(ret, GFP_KERNEL);
-	if (!tmp)
+	cbd = kzalloc(struct_size(cbd, blob, ret), GFP_KERNEL);
+	if (!cbd)
 		return -ENOMEM;
 
-	ret = xe_gt_sriov_pf_config_save(gt, vfid, tmp, ret);
-	if (ret > 0)
-		ret = simple_read_from_buffer(buf, count, pos, tmp, ret);
+	ret = xe_gt_sriov_pf_config_save(gt, vfid, cbd->blob, ret);
+	if (ret < 0) {
+		kfree(cbd);
+		return ret;
+	}
 
-	kfree(tmp);
-	return ret;
+	cbd->size = ret;
+	file->private_data = cbd;
+	return nonseekable_open(inode, file);
+}
+
+static ssize_t config_blob_read(struct file *file, char __user *buf,
+				size_t count, loff_t *pos)
+{
+	struct config_blob_data *cbd = file->private_data;
+
+	return simple_read_from_buffer(buf, count, pos, cbd->blob, cbd->size);
 }
 
 static ssize_t config_blob_write(struct file *file, const char __user *buf,
@@ -498,11 +513,18 @@ static ssize_t config_blob_write(struct file *file, const char __user *buf,
 	return ret;
 }
 
+static int config_blob_release(struct inode *inode, struct file *file)
+{
+	kfree(file->private_data);
+	return 0;
+}
+
 static const struct file_operations config_blob_ops = {
 	.owner		= THIS_MODULE,
+	.open		= config_blob_open,
 	.read		= config_blob_read,
 	.write		= config_blob_write,
-	.llseek		= default_llseek,
+	.release	= config_blob_release,
 };
 
 static void pf_add_compat_attrs(struct xe_gt *gt, struct dentry *dent, unsigned int vfid)