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

Andrew Morton
2021-11-05T20:44:56Z

From: David Hildenbrand <david@redhat.com>
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/20211004093605.5830-5-david@redhat.com
Signed-off-by: David Hildenbrand <david@redhat.com>
Reviewed-by: Mike Rapoport <rppt@linux.ibm.com>
Cc: "Aneesh Kumar K . V" <aneesh.kumar@linux.ibm.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Christian Borntraeger <borntraeger@de.ibm.com>
Cc: Eric Biederman <ebiederm@xmission.com>
Cc: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: Heiko Carstens <hca@linux.ibm.com>
Cc: Huacai Chen <chenhuacai@kernel.org>
Cc: Jianyong Wu <Jianyong.Wu@arm.com>
Cc: Jiaxun Yang <jiaxun.yang@flygoat.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Oscar Salvador <osalvador@suse.de>
Cc: Shahab Vahedi <shahab@synopsys.com>
Cc: Thomas Bogendoerfer <tsbogend@alpha.franken.de>
Cc: Vasily Gorbik <gor@linux.ibm.com>
Cc: Vineet Gupta <vgupta@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

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

--- 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;
}

_