On 28/08/26 15:19, Shivang Upadhyay wrote:
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.
Yes, as per PAPR, it is possible for the CPU data to be less than the
source length
due to CPU hotplug. Therefore, it is OK to accept bytes_dumped being
less than
source_len for the CPU region.
I have verified the changes and tested them on LPARs with different
partition configurations.
The dump collection went fine.
Feel free to add:
Reviewed-by: Sourabh Jain <[email protected]>
Reported-by: Anushree Mathur <[email protected]>
Closes:
https://lore.kernel.org/all/[email protected]/T/#u
Signed-off-by: Shivang Upadhyay <[email protected]>
---
Changelog:
v4:
removed extra blank line.
v3: https://lore.kernel.org/all/[email protected]/
removed extra variable.
v2: https://lore.kernel.org/all/[email protected]/
Only allowing lesser size for CPU_STATE_DATE Fadump region.
v1:
https://lore.kernel.org/qemu-devel/[email protected]/
---
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;
