[195/262] memblock: add MEMBLOCK_DRIVER_MANAGED to mimic IORESOURCE_SYSRAM_DRIVER_MANAGED

Commit Message

Andrew Morton Nov. 5, 2021, 8:44 p.m. UTC

From: David Hildenbrand <[e-mail]>
Subject: memblock: add MEMBLOCK_DRIVER_MANAGED to mimic IORESOURCE_SYSRAM_DRIVER_MANAGED

Let's add a flag that corresponds to IORESOURCE_SYSRAM_DRIVER_MANAGED,
indicating that we're dealing with a memory region that is never indicated
in the firmware-provided memory map, but always detected and added by a
driver.

Similar to MEMBLOCK_HOTPLUG, most infrastructure has to treat such memory
regions like ordinary MEMBLOCK_NONE memory regions -- for example, when
selecting memory regions to add to the vmcore for dumping in the
crashkernel via for_each_mem_range().

However, especially kexec_file is not supposed to select such memblocks
via for_each_free_mem_range() / for_each_free_mem_range_reverse() to place
kexec images, similar to how we handle IORESOURCE_SYSRAM_DRIVER_MANAGED
without CONFIG_ARCH_KEEP_MEMBLOCK.

We'll make sure that memory hotplug code sets the flag where applicable
(IORESOURCE_SYSRAM_DRIVER_MANAGED) next.  This prepares architectures that
need CONFIG_ARCH_KEEP_MEMBLOCK, such as arm64, for virtio-mem support.

Note that kexec *must not* indicate this memory to the second kernel and
*must not* place kexec-images on this memory.  Let's add a comment to
kexec_walk_memblock(), documenting how we handle MEMBLOCK_DRIVER_MANAGED
now just like using IORESOURCE_SYSRAM_DRIVER_MANAGED in
locate_mem_hole_callback() for kexec_walk_resources().

Also note that MEMBLOCK_HOTPLUG cannot be reused due to different
semantics:
	MEMBLOCK_HOTPLUG: memory is indicated as "System RAM" in the
	firmware-provided memory map and added to the system early during
	boot; kexec *has to* indicate this memory to the second kernel and
	can place kexec-images on this memory. After memory hotunplug,
	kexec has to be re-armed. We mostly ignore this flag when
	"movable_node" is not set on the kernel command line, because
	then we're told to not care about hotunpluggability of such
	memory regions.

	MEMBLOCK_DRIVER_MANAGED: memory is not indicated as "System RAM" in
	the firmware-provided memory map; this memory is always detected
	and added to the system by a driver; memory might not actually be
	physically hotunpluggable. kexec *must not* indicate this memory to
	the second kernel and *must not* place kexec-images on this memory.

Link: https://lkml.kernel.org/r/[e-mail]
Signed-off-by: David Hildenbrand <[e-mail]>
Reviewed-by: Mike Rapoport <[e-mail]>
Cc: "Aneesh Kumar K . V" <[e-mail]>
Cc: Arnd Bergmann <[e-mail]>
Cc: Christian Borntraeger <[e-mail]>
Cc: Eric Biederman <[e-mail]>
Cc: Geert Uytterhoeven <[e-mail]>
Cc: Heiko Carstens <[e-mail]>
Cc: Huacai Chen <[e-mail]>
Cc: Jianyong Wu <[e-mail]>
Cc: Jiaxun Yang <[e-mail]>
Cc: Michal Hocko <[e-mail]>
Cc: Oscar Salvador <[e-mail]>
Cc: Shahab Vahedi <[e-mail]>
Cc: Thomas Bogendoerfer <[e-mail]>
Cc: Vasily Gorbik <[e-mail]>
Cc: Vineet Gupta <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>
---

 include/linux/memblock.h |   16 ++++++++++++++--
 kernel/kexec_file.c      |    5 +++++
 mm/memblock.c            |    4 ++++
 3 files changed, 23 insertions(+), 2 deletions(-)

Patch

--- a/include/linux/memblock.h~memblock-add-memblock_driver_managed-to-mimic-ioresource_sysram_driver_managed
+++ a/include/linux/memblock.h
@@ -37,12 +37,17 @@  extern unsigned long long max_possible_p
  * @MEMBLOCK_NOMAP: don't add to kernel direct mapping and treat as
  * reserved in the memory map; refer to memblock_mark_nomap() description
  * for further details
+ * @MEMBLOCK_DRIVER_MANAGED: memory region that is always detected and added
+ * via a driver, and never indicated in the firmware-provided memory map as
+ * system RAM. This corresponds to IORESOURCE_SYSRAM_DRIVER_MANAGED in the
+ * kernel resource tree.
  */
 enum memblock_flags {
 	MEMBLOCK_NONE		= 0x0,	/* No special request */
 	MEMBLOCK_HOTPLUG	= 0x1,	/* hotpluggable region */
 	MEMBLOCK_MIRROR		= 0x2,	/* mirrored region */
 	MEMBLOCK_NOMAP		= 0x4,	/* don't add to kernel direct mapping */
+	MEMBLOCK_DRIVER_MANAGED = 0x8,	/* always detected via a driver */
 };
 
 /**
@@ -213,7 +218,8 @@  static inline void __next_physmem_range(
  */
 #define for_each_mem_range(i, p_start, p_end) \
 	__for_each_mem_range(i, &memblock.memory, NULL, NUMA_NO_NODE,	\
-			     MEMBLOCK_HOTPLUG, p_start, p_end, NULL)
+			     MEMBLOCK_HOTPLUG | MEMBLOCK_DRIVER_MANAGED, \
+			     p_start, p_end, NULL)
 
 /**
  * for_each_mem_range_rev - reverse iterate through memblock areas from
@@ -224,7 +230,8 @@  static inline void __next_physmem_range(
  */
 #define for_each_mem_range_rev(i, p_start, p_end)			\
 	__for_each_mem_range_rev(i, &memblock.memory, NULL, NUMA_NO_NODE, \
-				 MEMBLOCK_HOTPLUG, p_start, p_end, NULL)
+				 MEMBLOCK_HOTPLUG | MEMBLOCK_DRIVER_MANAGED,\
+				 p_start, p_end, NULL)
 
 /**
  * for_each_reserved_mem_range - iterate over all reserved memblock areas
@@ -254,6 +261,11 @@  static inline bool memblock_is_nomap(str
 	return m->flags & MEMBLOCK_NOMAP;
 }
 
+static inline bool memblock_is_driver_managed(struct memblock_region *m)
+{
+	return m->flags & MEMBLOCK_DRIVER_MANAGED;
+}
+
 int memblock_search_pfn_nid(unsigned long pfn, unsigned long *start_pfn,
 			    unsigned long  *end_pfn);
 void __next_mem_pfn_range(int *idx, int nid, unsigned long *out_start_pfn,
--- a/kernel/kexec_file.c~memblock-add-memblock_driver_managed-to-mimic-ioresource_sysram_driver_managed
+++ a/kernel/kexec_file.c
@@ -556,6 +556,11 @@  static int kexec_walk_memblock(struct ke
 	if (kbuf->image->type == KEXEC_TYPE_CRASH)
 		return func(&crashk_res, kbuf);
 
+	/*
+	 * Using MEMBLOCK_NONE will properly skip MEMBLOCK_DRIVER_MANAGED. See
+	 * IORESOURCE_SYSRAM_DRIVER_MANAGED handling in
+	 * locate_mem_hole_callback().
+	 */
 	if (kbuf->top_down) {
 		for_each_free_mem_range_reverse(i, NUMA_NO_NODE, MEMBLOCK_NONE,
 						&mstart, &mend, NULL) {
--- a/mm/memblock.c~memblock-add-memblock_driver_managed-to-mimic-ioresource_sysram_driver_managed
+++ a/mm/memblock.c
@@ -982,6 +982,10 @@  static bool should_skip_region(struct me
 	if (!(flags & MEMBLOCK_NOMAP) && memblock_is_nomap(m))
 		return true;
 
+	/* skip driver-managed memory unless we were asked for it explicitly */
+	if (!(flags & MEMBLOCK_DRIVER_MANAGED) && memblock_is_driver_managed(m))
+		return true;
+
 	return false;
 }