Automatic merge of 'next-test' into merge-test (2025-02-11 10:54)

Author: maddy-kerneldev

Documentation/ABI/testing/sysfs-kernel-fadump

@@ -55,4 +55,5 @@ Date:		May 2024
 Contact:	[email protected]
 Description:	read/write
 		This is a special sysfs file available to setup additional
-		parameters to be passed to capture kernel.
+		parameters to be passed to capture kernel. For HASH MMU it
+		is exported only if RMA size higher than 768MB.

Documentation/arch/powerpc/firmware-assisted-dump.rst

@@ -120,6 +120,28 @@ to ensure that crash data is preserved to process later.
    e.g.
      # echo 1 > /sys/firmware/opal/mpipl/release_core
 
+-- Support for Additional Kernel Arguments in Fadump
+   Fadump has a feature that allows passing additional kernel arguments
+   to the fadump kernel. This feature was primarily designed to disable
+   kernel functionalities that are not required for the fadump kernel
+   and to reduce its memory footprint while collecting the dump.
+
+  Command to Add Additional Kernel Parameters to Fadump:
+  e.g.
+  # echo "nr_cpus=16" > /sys/kernel/fadump/bootargs_append
+
+  The above command is sufficient to add additional arguments to fadump.
+  An explicit service restart is not required.
+
+  Command to Retrieve the Additional Fadump Arguments:
+  e.g.
+  # cat /sys/kernel/fadump/bootargs_append
+
+Note: Additional kernel arguments for fadump with HASH MMU is only
+      supported if the RMA size is greater than 768 MB. If the RMA
+      size is less than 768 MB, the kernel does not export the
+      /sys/kernel/fadump/bootargs_append sysfs node.
+
 Implementation details:
 -----------------------
 

arch/powerpc/include/asm/prom.h

@@ -17,6 +17,8 @@
 struct device_node;
 struct property;
 
+#define MIN_RMA			768		/* Minimum RMA (in MB) for CAS negotiation */
+
 #define OF_DT_BEGIN_NODE	0x1		/* Start of node, full name */
 #define OF_DT_END_NODE		0x2		/* End node */
 #define OF_DT_PROP		0x3		/* Property: name off, size,

arch/powerpc/kernel/fadump.c

@@ -33,6 +33,7 @@
 #include <asm/fadump-internal.h>
 #include <asm/setup.h>
 #include <asm/interrupt.h>
+#include <asm/prom.h>
 
 /*
  * The CPU who acquired the lock to trigger the fadump crash should
@@ -1764,19 +1765,19 @@ void __init fadump_setup_param_area(void)
 		range_end = memblock_end_of_DRAM();
 	} else {
 		/*
-		 * Passing additional parameters is supported for hash MMU only
-		 * if the first memory block size is 768MB or higher.
+		 * Memory range for passing additional parameters for HASH MMU
+		 * must meet the following conditions:
+		 * 1. The first memory block size must be higher than the
+		 *    minimum RMA (MIN_RMA) size. Bootloader can use memory
+		 *    upto RMA size. So it should be avoided.
+		 * 2. The range should be between MIN_RMA and RMA size (ppc64_rma_size)
+		 * 3. It must not overlap with the fadump reserved area.
 		 */
-		if (ppc64_rma_size < 0x30000000)
+		if (ppc64_rma_size < MIN_RMA*1024*1024)
 			return;
 
-		/*
-		 * 640 MB to 768 MB is not used by PFW/bootloader. So, try reserving
-		 * memory for passing additional parameters in this range to avoid
-		 * being stomped on by PFW/bootloader.
-		 */
-		range_start = 0x2A000000;
-		range_end = range_start + 0x4000000;
+		range_start = MIN_RMA * 1024 * 1024;
+		range_end = min(ppc64_rma_size, fw_dump.boot_mem_top);
 	}
 
 	fw_dump.param_area = memblock_phys_alloc_range(COMMAND_LINE_SIZE,

arch/powerpc/kernel/prom_init.c

@@ -1061,7 +1061,7 @@ static const struct ibm_arch_vec ibm_architecture_vec_template __initconst = {
 		.virt_base = cpu_to_be32(0xffffffff),
 		.virt_size = cpu_to_be32(0xffffffff),
 		.load_base = cpu_to_be32(0xffffffff),
-		.min_rma = cpu_to_be32(512),		/* 512MB min RMA */
+		.min_rma = cpu_to_be32(MIN_RMA),
 		.min_load = cpu_to_be32(0xffffffff),	/* full client load */
 		.min_rma_percent = 0,	/* min RMA percentage of total RAM */
 		.max_pft_size = 48,	/* max log_2(hash table size) */