[PATCH v2] powerpc/fadump: Add timeout to RTAS busy-wait loops

Adriano Vero
2026-04-19T12:40:18Z

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 <adri.vero.dev@gmail.com>
---
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 eceb32893..3bb4ac2ab 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 c109abf6b..65fdab7b5 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