[PATCH v4] ppc/fadump: collect dump when CPU_STATE_DATA is less than reserved
From: Shivang Upadhyay <hidden>
Date: 2026-08-28 09:50:12
Also in:
lkml
Subsystem:
linux for powerpc (32-bit and 64-bit), the rest · Maintainers:
Madhavan Srinivasan, Linus Torvalds
During Fadump in Qemu VM, when maxcpus value is set to more than current
cpus, following failure is observed.
[ 0.045806] [ T1] rtas fadump: Dump taken by platform is
incomplete (0)
This is because the CPU_STATE_DATA is allocated for maxcpus, while the
data is only filled for current cpus. As per current implementation
of Fadump, dumped_bytes and source_len for a region have to match,
Which is failing for qemu's case, Even tough the dumped bytes are
reported correctly for only the current cpus. After this /proc/vmcore
generatition also fails.
Allowing dumped_bytes to be lesser than or equal to allocated length, for
CPU_STATE_DATA Fadump region.
Reported-by: Anushree Mathur <redacted>
Closes: https://lore.kernel.org/all/5e66daf4-3f55-4044-94a5-4f50bb040849@linux.ibm.com/T/#u (local)
Signed-off-by: Shivang Upadhyay <redacted>
---
Changelog:
v4:
removed extra blank line.
v3: https://lore.kernel.org/all/20260827075803.2240934-1-shivangu@linux.ibm.com/ (local)
removed extra variable.
v2: https://lore.kernel.org/all/20260826125626.2108771-1-shivangu@linux.ibm.com/ (local)
Only allowing lesser size for CPU_STATE_DATE Fadump region.
v1: https://lore.kernel.org/qemu-devel/20260429065127.366813-1-shivangu@linux.ibm.com/ (local)
---
arch/powerpc/platforms/pseries/rtas-fadump.c | 16 ++++++++++++++--
1 file changed, 14 insertions(+), 2 deletions(-)
diff --git a/arch/powerpc/platforms/pseries/rtas-fadump.c b/arch/powerpc/platforms/pseries/rtas-fadump.c
index 3bb4ac2ab6cc..838e97c24308 100644
--- a/arch/powerpc/platforms/pseries/rtas-fadump.c
+++ b/arch/powerpc/platforms/pseries/rtas-fadump.c@@ -459,6 +459,8 @@ static int __init rtas_fadump_process(struct fw_dump *fadump_conf) /* Check if the dump data is valid. */ for (int i = 0; i < be16_to_cpu(fdm_active->header.dump_num_sections); i++) { int type = be16_to_cpu(fdm_active->rgn[i].source_data_type); + uint64_t bytes_dumped = be64_to_cpu(fdm_active->rgn[i].bytes_dumped); + uint64_t source_len = be64_to_cpu(fdm_active->rgn[i].source_len); int rc = 0; switch (type) {
@@ -469,10 +471,20 @@ static int __init rtas_fadump_process(struct fw_dump *fadump_conf) pr_err("Dump taken by platform is not valid (%d)\n", i); rc = -EINVAL; } - if (fdm_active->rgn[i].bytes_dumped != fdm_active->rgn[i].source_len) { + + /* + * Make sure that dump is collected for entire region. + * CPU_STATE_DATA region is allowed to dump less than allocated space. + */ + if (!(bytes_dumped == source_len || + (type == RTAS_FADUMP_CPU_STATE_DATA && bytes_dumped <= source_len))) { + pr_err("Dump taken by platform is incomplete (%d)\n", i); + pr_debug("type -> %d, bytes_dumped -> %llx, source_len -> %llx\n", + type, bytes_dumped, source_len); rc = -EINVAL; } + if (rc) { pr_warn("Region type: %u src addr: 0x%llx dest addr: 0x%llx\n", be16_to_cpu(fdm_active->rgn[i].source_data_type),
@@ -482,7 +494,7 @@ static int __init rtas_fadump_process(struct fw_dump *fadump_conf) } break; case RTAS_FADUMP_PARAM_AREA: - if (fdm_active->rgn[i].bytes_dumped != fdm_active->rgn[i].source_len || + if (bytes_dumped != source_len || fdm_active->rgn[i].error_flags != 0) { pr_warn("Failed to process additional parameters! Proceeding anyway..\n"); fadump_conf->param_area = 0;
--
2.54.0