[PATCH] drm/imagination: Improve logging of unknown freelist IDs

[PATCH] drm/imagination: Improve logging of unknown freelist IDs

[Alexandru Dadu]

From: Alessio Belle <alessio.belle@imgtec.com>

Log freelist IDs not recognised by the driver when processing freelist
grow or reconstruction requests from the firmware.

In the freelist grow request path, remove a WARN_ON() which is not
particularly useful since it is known where the request came from.

Signed-off-by: Alessio Belle <alessio.belle@imgtec.com>
Signed-off-by: Alexandru Dadu <alexandru.dadu@imgtec.com>
---
 drivers/gpu/drm/imagination/pvr_free_list.c | 13 +++++++++++--
 1 file changed, 11 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/imagination/pvr_free_list.c b/drivers/gpu/drm/imagination/pvr_free_list.c
index e85cac83834c..f8a333649933 100644
--- a/drivers/gpu/drm/imagination/pvr_free_list.c
+++ b/drivers/gpu/drm/imagination/pvr_free_list.c
@@ -8,6 +8,7 @@
 #include "pvr_vm.h"
 
 #include <drm/drm_gem.h>
+#include <drm/drm_print.h>
 #include <linux/slab.h>
 #include <linux/xarray.h>
 #include <uapi/drm/pvr_drm.h>
@@ -367,8 +368,12 @@ void pvr_free_list_process_grow_req(struct pvr_device *pvr_dev,
 	u32 grow_pages = 0;
 
 	/* If we don't have a freelist registered for this ID, we can't do much. */
-	if (WARN_ON(!free_list))
+	if (!free_list) {
+		drm_warn(from_pvr_device(pvr_dev),
+			 "Received freelist grow request for unknown ID 0x%x\n",
+			 req->freelist_id);
 		return;
+	}
 
 	/* Since the FW made the request, it has already consumed the ready pages,
 	 * update the host struct.
@@ -564,8 +569,12 @@ pvr_free_list_reconstruct(struct pvr_device *pvr_dev, u32 freelist_id)
 	struct rogue_fwif_freelist *fw_data;
 	struct pvr_hwrt_data *hwrt_data;
 
-	if (!free_list)
+	if (!free_list) {
+		drm_warn(from_pvr_device(pvr_dev),
+			 "Received freelist reconstruction request for unknown ID 0x%x\n",
+			 freelist_id);
 		return;
+	}
 
 	mutex_lock(&free_list->lock);
 

---
base-commit: 6e375de99d0c420169481fcd36064177ab55b09d
change-id: 20261006-b4-improve-logging-of-unknown-freelist-ids-8a69777fd61e

Best regards,
--  
Alexandru Dadu <alexandru.dadu@imgtec.com>

Re: [PATCH] drm/imagination: Improve logging of unknown freelist IDs

[sashiko-bot]

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
- [Medium] drm: missing rate-limiting on firmware-driven log messages
--

commit 48839b908b6b2c9825c18cddcc77e1ed32786c07
Author: Alessio Belle <alessio.belle@imgtec.com>
drm/imagination: Improve logging of unknown freelist IDs

This commit improves logging by adding warnings when the firmware sends
freelist grow or reconstruction requests with unrecognized IDs. It also
removes a WARN_ON() in the grow request path.

> diff --git a/drivers/gpu/drm/imagination/pvr_free_list.c b/drivers/gpu/drm/imagination/pvr_free_list.c
> index e85cac83834c6..f8a333649933a 100644
> --- a/drivers/gpu/drm/imagination/pvr_free_list.c
> +++ b/drivers/gpu/drm/imagination/pvr_free_list.c
[ ... ]
> @@ -367,8 +368,12 @@ void pvr_free_list_process_grow_req(struct pvr_device *pvr_dev,
>  	u32 grow_pages = 0;
>  
>  	/* If we don't have a freelist registered for this ID, we can't do much. */
> -	if (WARN_ON(!free_list))
> +	if (!free_list) {
> +		drm_warn(from_pvr_device(pvr_dev),
> +			 "Received freelist grow request for unknown ID 0x%x\n",
> +			 req->freelist_id);

[Severity: Medium]
Could this lead to log flooding if the firmware repeatedly sends requests
with an unknown freelist ID?

While the firmware is trusted, it is generally standard practice to use
drm_warn_ratelimited() for messages triggered by hardware or firmware
events to prevent kernel log buffer overflows.

>  		return;
> +	}
>  
>  	/* Since the FW made the request, it has already consumed the ready pages,
>  	 * update the host struct.
[ ... ]
> @@ -564,8 +569,12 @@ pvr_free_list_reconstruct(struct pvr_device *pvr_dev, u32 freelist_id)
>  	struct rogue_fwif_freelist *fw_data;
>  	struct pvr_hwrt_data *hwrt_data;
>  
> -	if (!free_list)
> +	if (!free_list) {
> +		drm_warn(from_pvr_device(pvr_dev),
> +			 "Received freelist reconstruction request for unknown ID 0x%x\n",
> +			 freelist_id);

[Severity: Medium]
Similarly, could this unbounded warning consume CPU cycles and mask other
important errors if the firmware malfunctions or is compromised?

Using a rate limited logging function here might be safer.

>  		return;
> +	}
>  
>  	mutex_lock(&free_list->lock);
>

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20261006-b4-improve-logging-of-unknown-freelist-ids-v1-1-96ebcb132b80@imgtec.com?part=1