powerpc/fadump: support copying multiple kernel boot memory regions

Firmware uses a 32-bit field for size while copying/backing-up memory
during MPIPL. So, the maximum value that could be represented with
a PAGE_SIZE aligned 32-bit field will be the maximum copy size for a
region but FADump capture kernel usually needs more memory than that
to be preserved to avoid running into out of memory errors.

So, request firmware to copy multiple kernel boot memory regions
instead of just one (which worked fine for pseries as 64-bit field
was used for size there).
Signed-off-by: Hari Bathini <hbathini@linux.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/156821350193.5656.3664853158523582019.stgit@hbathini.in.ibm.com

arch/powerpc/platforms/powernv/opal-fadump.c

@@ -26,6 +26,8 @@ static int opal_fadump_unregister(struct fw_dump *fadump_conf);
 static void opal_fadump_update_config(struct fw_dump *fadump_conf,
 				      const struct opal_fadump_mem_struct *fdm)
 {
+	pr_debug("Boot memory regions count: %d\n", fdm->region_cnt);
+
 	/*
 	 * The destination address of the first boot memory region is the
 	 * destination address of boot memory regions.
@@ -48,16 +50,34 @@ static void opal_fadump_init_metadata(struct opal_fadump_mem_struct *fdm)
 
 static u64 opal_fadump_init_mem_struct(struct fw_dump *fadump_conf)
 {
-	u64 addr = fadump_conf->reserve_dump_area_start;
+	int max_copy_size, cur_size, size;
+	u64 src_addr, dest_addr;
 
 	opal_fdm = __va(fadump_conf->kernel_metadata);
 	opal_fadump_init_metadata(opal_fdm);
 
-	opal_fdm->region_cnt = 1;
-	opal_fdm->rgn[0].src	= 0;
-	opal_fdm->rgn[0].dest	= addr;
-	opal_fdm->rgn[0].size	= fadump_conf->boot_memory_size;
-	addr += fadump_conf->boot_memory_size;
+	/*
+	 * Firmware supports 32-bit field for size. Align it to PAGE_SIZE
+	 * and request firmware to copy multiple kernel boot memory regions.
+	 */
+	max_copy_size = _ALIGN_DOWN(U32_MAX, PAGE_SIZE);
+
+	/* Boot memory regions */
+	src_addr = 0;
+	dest_addr = fadump_conf->reserve_dump_area_start;
+	size = fadump_conf->boot_memory_size;
+	while (size) {
+		cur_size = size > max_copy_size ? max_copy_size : size;
+
+		opal_fdm->rgn[opal_fdm->region_cnt].src  = src_addr;
+		opal_fdm->rgn[opal_fdm->region_cnt].dest = dest_addr;
+		opal_fdm->rgn[opal_fdm->region_cnt].size = cur_size;
+
+		opal_fdm->region_cnt++;
+		dest_addr	+= cur_size;
+		src_addr	+= cur_size;
+		size		-= cur_size;
+	}
 
 	/*
 	 * Kernel metadata is passed to f/w and retrieved in capture kerenl.
@@ -68,7 +88,7 @@ static u64 opal_fadump_init_mem_struct(struct fw_dump *fadump_conf)
 
 	opal_fadump_update_config(fadump_conf, opal_fdm);
 
-	return addr;
+	return dest_addr;
 }
 
 static u64 opal_fadump_get_metadata_size(void)