powerpc/fadump: setup additional parameters for dump capture kernel

For fadump case, passing additional parameters to dump capture kernel
helps in minimizing the memory footprint for it and also provides the
flexibility to disable components/modules, like hugepages, that are
hindering the boot process of the special dump capture environment.

Set up a dedicated parameter area to be passed to the capture kernel.
This area type is defined as RTAS_FADUMP_PARAM_AREA. Sysfs attribute
'/sys/kernel/fadump/bootargs_append' is exported to the userspace to
specify the additional parameters to be passed to the capture kernel

Signed-off-by: Hari Bathini <hbathini@linux.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://msgid.link/20240509115755.519982-3-hbathini@linux.ibm.com

3 files changed, 43 insertions, 9 deletions

diff --git a/arch/powerpc/platforms/powernv/opal-fadump.c b/arch/powerpc/platforms/powernv/opal-fadump.c
index 5a88d7efb48a..c9c1dfb35464 100644
--- a/arch/powerpc/platforms/powernv/opal-fadump.c
+++ b/arch/powerpc/platforms/powernv/opal-fadump.c
@@ -665,8 +665,10 @@ void __init opal_fadump_dt_scan(struct fw_dump *fadump_conf, u64 node)
 		}
 	}
 
-	fadump_conf->ops		= &opal_fadump_ops;
-	fadump_conf->fadump_supported	= 1;
+	fadump_conf->ops			= &opal_fadump_ops;
+	fadump_conf->fadump_supported		= 1;
+	/* TODO: Add support to pass additional parameters */
+	fadump_conf->param_area_supported	= 0;
 
 	/*
 	 * Firmware supports 32-bit field for size. Align it to PAGE_SIZE
diff --git a/arch/powerpc/platforms/pseries/rtas-fadump.c b/arch/powerpc/platforms/pseries/rtas-fadump.c
index 4db78b2bb2a8..eceb3289383e 100644
--- a/arch/powerpc/platforms/pseries/rtas-fadump.c
+++ b/arch/powerpc/platforms/pseries/rtas-fadump.c
@@ -18,6 +18,7 @@
 
 #include <asm/page.h>
 #include <asm/rtas.h>
+#include <asm/setup.h>
 #include <asm/fadump.h>
 #include <asm/fadump-internal.h>
 
@@ -81,6 +82,9 @@ static void __init rtas_fadump_get_config(struct fw_dump *fadump_conf,
 			last_end = base + size;
 			fadump_conf->boot_mem_regs_cnt++;
 			break;
+		case RTAS_FADUMP_PARAM_AREA:
+			fadump_conf->param_area = be64_to_cpu(fdm->rgn[i].destination_address);
+			break;
 		default:
 			pr_warn("Section type %d unsupported on this kernel. Ignoring!\n", type);
 			break;
@@ -154,7 +158,17 @@ static u64 rtas_fadump_init_mem_struct(struct fw_dump *fadump_conf)
 		sec_cnt++;
 	}
 
+	/* Parameters area */
+	if (fadump_conf->param_area) {
+		fdm.rgn[sec_cnt].request_flag = cpu_to_be32(RTAS_FADUMP_REQUEST_FLAG);
+		fdm.rgn[sec_cnt].source_data_type = cpu_to_be16(RTAS_FADUMP_PARAM_AREA);
+		fdm.rgn[sec_cnt].source_address = cpu_to_be64(fadump_conf->param_area);
+		fdm.rgn[sec_cnt].source_len = cpu_to_be64(COMMAND_LINE_SIZE);
+		fdm.rgn[sec_cnt].destination_address = cpu_to_be64(fadump_conf->param_area);
+		sec_cnt++;
+	}
 	fdm.header.dump_num_sections = cpu_to_be16(sec_cnt);
+
 	rtas_fadump_update_config(fadump_conf, &fdm);
 
 	return addr;
@@ -453,6 +467,13 @@ static int __init rtas_fadump_process(struct fw_dump *fadump_conf)
 				return rc;
 			}
 			break;
+		case RTAS_FADUMP_PARAM_AREA:
+			if (fdm_active->rgn[i].bytes_dumped != fdm_active->rgn[i].source_len ||
+			    fdm_active->rgn[i].error_flags != 0) {
+				pr_warn("Failed to process additional parameters! Proceeding anyway..\n");
+				fadump_conf->param_area = 0;
+			}
+			break;
 		default:
 			/*
 			 * If the first/crashed kernel added a new region type that the
@@ -509,6 +530,13 @@ static void rtas_fadump_region_show(struct fw_dump *fadump_conf,
 				   be64_to_cpu(fdm_ptr->rgn[i].source_len),
 				   be64_to_cpu(fdm_ptr->rgn[i].bytes_dumped));
 			break;
+		case RTAS_FADUMP_PARAM_AREA:
+			seq_printf(m, "\n[%#016llx-%#016llx]: cmdline append: '%s'\n",
+				   be64_to_cpu(fdm_ptr->rgn[i].destination_address),
+				   be64_to_cpu(fdm_ptr->rgn[i].destination_address) +
+				   be64_to_cpu(fdm_ptr->rgn[i].source_len) - 1,
+				   (char *)__va(be64_to_cpu(fdm_ptr->rgn[i].destination_address)));
+			break;
 		default:
 			seq_printf(m, "Unknown region type %d : Src: %#016llx, Dest: %#016llx, ",
 				   type, be64_to_cpu(fdm_ptr->rgn[i].source_address),
@@ -571,9 +599,10 @@ void __init rtas_fadump_dt_scan(struct fw_dump *fadump_conf, u64 node)
 	if (!token)
 		return;
 
-	fadump_conf->ibm_configure_kernel_dump = be32_to_cpu(*token);
-	fadump_conf->ops		= &rtas_fadump_ops;
-	fadump_conf->fadump_supported	= 1;
+	fadump_conf->ibm_configure_kernel_dump	= be32_to_cpu(*token);
+	fadump_conf->ops			= &rtas_fadump_ops;
+	fadump_conf->fadump_supported		= 1;
+	fadump_conf->param_area_supported	= 1;
 
 	/* Firmware supports 64-bit value for size, align it to pagesize. */
 	fadump_conf->max_copy_size = ALIGN_DOWN(U64_MAX, PAGE_SIZE);
diff --git a/arch/powerpc/platforms/pseries/rtas-fadump.h b/arch/powerpc/platforms/pseries/rtas-fadump.h
index 6740f4981bb8..c109abf6befd 100644
--- a/arch/powerpc/platforms/pseries/rtas-fadump.h
+++ b/arch/powerpc/platforms/pseries/rtas-fadump.h
@@ -23,6 +23,9 @@
 #define RTAS_FADUMP_HPTE_REGION		0x0002
 #define RTAS_FADUMP_REAL_MODE_REGION	0x0011
 
+/* OS defined sections */
+#define RTAS_FADUMP_PARAM_AREA		0x0100
+
 /* Dump request flag */
 #define RTAS_FADUMP_REQUEST_FLAG	0x00000001
 
@@ -31,12 +34,12 @@
 
 /*
  * The Firmware Assisted Dump Memory structure supports a maximum of 10 sections
- * in the dump memory structure. Presently, first two sections are used for
- * CPU and HPTE data, while the remaining eight sections can be used for
- * boot memory regions.
+ * in the dump memory structure. Presently, three sections are used for
+ * CPU state data, HPTE & Parameters area, while the remaining seven sections
+ * can be used for boot memory regions.
  */
 #define MAX_SECTIONS				10
-#define RTAS_FADUMP_MAX_BOOT_MEM_REGS		8
+#define RTAS_FADUMP_MAX_BOOT_MEM_REGS		7
 
 /* Kernel Dump section info */
 struct rtas_fadump_section {