[PATCH AUTOSEL 6.18-6.12] powerpc/fadump: Add timeout to RTAS busy-wait loops

From: Adriano Vero <[email protected]>

[ Upstream commit b3580dd1c68cec23d44a39c439e18b4686c13480 ]

The ibm,configure-kernel-dump RTAS call sites in
rtas_fadump_register(), rtas_fadump_unregister(), and
rtas_fadump_invalidate() polled indefinitely while firmware returned
a busy status. A misbehaving or hung firmware could stall these paths
forever, blocking fadump registration at boot or preventing clean
teardown.

Introduce rtas_fadump_call(), a helper that wraps the common
busy-wait pattern shared by all three sites. The helper accumulates
the total delay and returns -ETIMEDOUT if firmware keeps returning a
busy status beyond RTAS_FADUMP_MAX_WAIT_MS (60 seconds). A pr_debug()
message is emitted on each busy iteration to aid diagnosis when the
timeout is hit.

Signed-off-by: Adriano Vero <[email protected]>
Reviewed-by: Sourabh Jain <[email protected]>
[Maddy: Fixed newline after Signed-off-by]
Signed-off-by: Madhavan Srinivasan <[email protected]>
Link: https://patch.msgid.link/[email protected]
Signed-off-by: Sasha Levin <[email protected]>
---

LLM Generated explanations, may be completely bogus:

Both background searches finished and match the earlier analysis:

- **No timeout fix in this tree** — searches for `"upper time limit"`,
  `"rtas_fadump_call"`, and `"timeout to RTAS busy-wait"` returned
  nothing.
- The only hit from the broader `"fadump.*timeout"` search was
  unrelated: `ba608c4fa12cf` (pstore/fadump race fix).

So the unbounded RTAS busy-wait loops with the `TODO` comments are still
present in **6.18.44**, and the timeout patch would be a new backport.
The prior **YES** recommendation stands.

 arch/powerpc/platforms/pseries/rtas-fadump.c | 80 ++++++++++++--------
 arch/powerpc/platforms/pseries/rtas-fadump.h |  6 ++
 2 files changed, 53 insertions(+), 33 deletions(-)

diff --git a/arch/powerpc/platforms/pseries/rtas-fadump.c b/arch/powerpc/platforms/pseries/rtas-fadump.c
index eceb3289383ec..3bb4ac2ab6cc3 100644
--- a/arch/powerpc/platforms/pseries/rtas-fadump.c
+++ b/arch/powerpc/platforms/pseries/rtas-fadump.c
@@ -179,9 +179,42 @@ static u64 rtas_fadump_get_bootmem_min(void)
 	return RTAS_FADUMP_MIN_BOOT_MEM;
 }
 
+/*
+ * Helper to make an ibm,configure-kernel-dump RTAS call with a bounded
+ * busy-wait loop. Returns the RTAS return code on completion, or
+ * -ETIMEDOUT if firmware keeps returning a busy status beyond
+ * RTAS_FADUMP_MAX_WAIT_MS milliseconds.
+ */
+static int rtas_fadump_call(struct fw_dump *fadump_conf, int operation,
+			    void *fdm_ptr, unsigned int fdm_size,
+			    const char *op_name)
+{
+	unsigned int wait_time, total_wait = 0;
+	int rc;
+
+	do {
+		rc = rtas_call(fadump_conf->ibm_configure_kernel_dump, 3, 1,
+			       NULL, operation, fdm_ptr, fdm_size);
+		wait_time = rtas_busy_delay_time(rc);
+		if (wait_time) {
+			pr_debug("Firmware busy during fadump %s, waiting %ums (total %ums)\n",
+				 op_name, wait_time, total_wait);
+			if (total_wait >= RTAS_FADUMP_MAX_WAIT_MS) {
+				pr_err("Timed out waiting for firmware to complete fadump %s\n",
+				       op_name);
+				return -ETIMEDOUT;
+			}
+			total_wait += wait_time;
+			mdelay(wait_time);
+		}
+	} while (wait_time);
+
+	return rc;
+}
+
 static int rtas_fadump_register(struct fw_dump *fadump_conf)
 {
-	unsigned int wait_time, fdm_size;
+	unsigned int fdm_size;
 	int rc, err = -EIO;
 
 	/*
@@ -192,16 +225,10 @@ static int rtas_fadump_register(struct fw_dump *fadump_conf)
 	fdm_size = sizeof(struct rtas_fadump_section_header);
 	fdm_size += be16_to_cpu(fdm.header.dump_num_sections) * sizeof(struct rtas_fadump_section);
 
-	/* TODO: Add upper time limit for the delay */
-	do {
-		rc =  rtas_call(fadump_conf->ibm_configure_kernel_dump, 3, 1,
-				NULL, FADUMP_REGISTER, &fdm, fdm_size);
-
-		wait_time = rtas_busy_delay_time(rc);
-		if (wait_time)
-			mdelay(wait_time);
-
-	} while (wait_time);
+	rc = rtas_fadump_call(fadump_conf, FADUMP_REGISTER, &fdm, fdm_size,
+			      "register");
+	if (rc == -ETIMEDOUT)
+		return -ETIMEDOUT;
 
 	switch (rc) {
 	case 0:
@@ -234,19 +261,12 @@ static int rtas_fadump_register(struct fw_dump *fadump_conf)
 
 static int rtas_fadump_unregister(struct fw_dump *fadump_conf)
 {
-	unsigned int wait_time;
 	int rc;
 
-	/* TODO: Add upper time limit for the delay */
-	do {
-		rc =  rtas_call(fadump_conf->ibm_configure_kernel_dump, 3, 1,
-				NULL, FADUMP_UNREGISTER, &fdm,
-				sizeof(struct rtas_fadump_mem_struct));
-
-		wait_time = rtas_busy_delay_time(rc);
-		if (wait_time)
-			mdelay(wait_time);
-	} while (wait_time);
+	rc = rtas_fadump_call(fadump_conf, FADUMP_UNREGISTER, &fdm,
+			      sizeof(struct rtas_fadump_mem_struct), "unregister");
+	if (rc == -ETIMEDOUT)
+		return -ETIMEDOUT;
 
 	if (rc) {
 		pr_err("Failed to un-register - unexpected error(%d).\n", rc);
@@ -259,19 +279,13 @@ static int rtas_fadump_unregister(struct fw_dump *fadump_conf)
 
 static int rtas_fadump_invalidate(struct fw_dump *fadump_conf)
 {
-	unsigned int wait_time;
 	int rc;
 
-	/* TODO: Add upper time limit for the delay */
-	do {
-		rc =  rtas_call(fadump_conf->ibm_configure_kernel_dump, 3, 1,
-				NULL, FADUMP_INVALIDATE, fdm_active,
-				sizeof(struct rtas_fadump_mem_struct));
-
-		wait_time = rtas_busy_delay_time(rc);
-		if (wait_time)
-			mdelay(wait_time);
-	} while (wait_time);
+	rc = rtas_fadump_call(fadump_conf, FADUMP_INVALIDATE,
+			      (void *)fdm_active,
+			      sizeof(struct rtas_fadump_mem_struct), "invalidate");
+	if (rc == -ETIMEDOUT)
+		return -ETIMEDOUT;
 
 	if (rc) {
 		pr_err("Failed to invalidate - unexpected error (%d).\n", rc);
diff --git a/arch/powerpc/platforms/pseries/rtas-fadump.h b/arch/powerpc/platforms/pseries/rtas-fadump.h
index c109abf6befd9..65fdab7b5b8d3 100644
--- a/arch/powerpc/platforms/pseries/rtas-fadump.h
+++ b/arch/powerpc/platforms/pseries/rtas-fadump.h
@@ -41,6 +41,12 @@
 #define MAX_SECTIONS				10
 #define RTAS_FADUMP_MAX_BOOT_MEM_REGS		7
 
+/*
+ * Maximum time to wait for firmware to respond to an
+ * ibm,configure-kernel-dump RTAS call before giving up.
+ */
+#define RTAS_FADUMP_MAX_WAIT_MS			60000U
+
 /* Kernel Dump section info */
 struct rtas_fadump_section {
 	__be32	request_flag;
-- 
2.53.0