powerpc/fadump: Warn before processing partial crashdump

If all kernel boot memory regions are not registered for MPIPL before
system crashes, try processing the partial crashdump but warn the user
before proceeding.

Signed-off-by: Hari Bathini <hbathini@linux.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/156821352793.5656.1734051341024721407.stgit@hbathini.in.ibm.com

diff --git a/arch/powerpc/platforms/powernv/opal-fadump.c b/arch/powerpc/platforms/powernv/opal-fadump.c
index 5ace7c4d6bc168d5d441dcc538f79cd9c1a768d0..533adae545d8a07d8bc1ca6f651245e5b9919f2c 100644 (file)
--- a/arch/powerpc/platforms/powernv/opal-fadump.c
+++ b/arch/powerpc/platforms/powernv/opal-fadump.c
@@ -69,6 +69,30 @@ static void opal_fadump_get_config(struct fw_dump *fadump_conf,
         */
        fadump_conf->reserve_dump_area_start = fdm->rgn[0].dest;
 
+       /*
+        * Rarely, but it can so happen that system crashes before all
+        * boot memory regions are registered for MPIPL. In such
+        * cases, warn that the vmcore may not be accurate and proceed
+        * anyway as that is the best bet considering free pages, cache
+        * pages, user pages, etc are usually filtered out.
+        *
+        * Hope the memory that could not be preserved only has pages
+        * that are usually filtered out while saving the vmcore.
+        */
+       if (fdm->region_cnt > fdm->registered_regions) {
+               pr_warn("Not all memory regions were saved!!!\n");
+               pr_warn("  Unsaved memory regions:\n");
+               i = fdm->registered_regions;
+               while (i < fdm->region_cnt) {
+                       pr_warn("\t[%03d] base: 0x%llx, size: 0x%llx\n",
+                               i, fdm->rgn[i].src, fdm->rgn[i].size);
+                       i++;
+               }
+
+               pr_warn("If the unsaved regions only contain pages that are filtered out (eg. free/user pages), the vmcore should still be usable.\n");
+               pr_warn("WARNING: If the unsaved regions contain kernel pages, the vmcore will be corrupted.\n");
+       }
+
        opal_fadump_update_config(fadump_conf, fdm);
 }