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From: David Hildenbrand <david@redhat.com>
To: linux-kernel@vger.kernel.org
Cc: David Hildenbrand <david@redhat.com>,
	Andrew Morton <akpm@linux-foundation.org>,
	Mike Rapoport <rppt@kernel.org>, Michal Hocko <mhocko@suse.com>,
	Oscar Salvador <osalvador@suse.de>,
	Jianyong Wu <Jianyong.Wu@arm.com>,
	"Aneesh Kumar K . V" <aneesh.kumar@linux.ibm.com>,
	Vineet Gupta <vgupta@kernel.org>,
	Geert Uytterhoeven <geert@linux-m68k.org>,
	Huacai Chen <chenhuacai@kernel.org>,
	Jiaxun Yang <jiaxun.yang@flygoat.com>,
	Thomas Bogendoerfer <tsbogend@alpha.franken.de>,
	Heiko Carstens <hca@linux.ibm.com>,
	Vasily Gorbik <gor@linux.ibm.com>,
	Christian Borntraeger <borntraeger@de.ibm.com>,
	Eric Biederman <ebiederm@xmission.com>,
	Arnd Bergmann <arnd@arndb.de>,
	linux-snps-arc@lists.infradead.org, linux-ia64@vger.kernel.org,
	linux-m68k@lists.linux-m68k.org, linux-mips@vger.kernel.org,
	linux-s390@vger.kernel.org, linux-mm@kvack.org,
	kexec@lists.infradead.org
Subject: [PATCH v1 3/4] memblock: add MEMBLOCK_DRIVER_MANAGED to mimic IORESOURCE_SYSRAM_DRIVER_MANAGED
Date: Mon, 27 Sep 2021 17:05:17 +0200	[thread overview]
Message-ID: <20210927150518.8607-4-david@redhat.com> (raw)
In-Reply-To: <20210927150518.8607-1-david@redhat.com>

Let's add a flag that corresponds to IORESOURCE_SYSRAM_DRIVER_MANAGED.
Similar to MEMBLOCK_HOTPLUG, most infrastructure has to treat such memory
like ordinary MEMBLOCK_NONE memory -- 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.

Let's document why kexec_walk_memblock() won't try placing images on
areas marked MEMBLOCK_DRIVER_MANAGED -- similar to
IORESOURCE_SYSRAM_DRIVER_MANAGED handling in locate_mem_hole_callback()
via kexec_walk_resources().

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.

Signed-off-by: David Hildenbrand <david@redhat.com>
---
 include/linux/memblock.h | 16 ++++++++++++++--
 kernel/kexec_file.c      |  5 +++++
 mm/memblock.c            |  4 ++++
 3 files changed, 23 insertions(+), 2 deletions(-)

diff --git a/include/linux/memblock.h b/include/linux/memblock.h
index b49a58f621bc..7d8d656d5082 100644
--- a/include/linux/memblock.h
+++ b/include/linux/memblock.h
@@ -33,12 +33,17 @@ extern unsigned long long max_possible_pfn;
  * @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 via a driver,
+ * corresponding to IORESOURCE_SYSRAM_DRIVER_MANAGED in the kernel resource
+ * tree. Especially kexec should never use this memory for placing images and
+ * shouldn't expose this memory to the second kernel.
  */
 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 */
 };
 
 /**
@@ -209,7 +214,8 @@ static inline void __next_physmem_range(u64 *idx, struct memblock_type *type,
  */
 #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
@@ -220,7 +226,8 @@ static inline void __next_physmem_range(u64 *idx, struct memblock_type *type,
  */
 #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
@@ -250,6 +257,11 @@ static inline bool memblock_is_nomap(struct memblock_region *m)
 	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,
diff --git a/kernel/kexec_file.c b/kernel/kexec_file.c
index 33400ff051a8..8347fc158d2b 100644
--- a/kernel/kexec_file.c
+++ b/kernel/kexec_file.c
@@ -556,6 +556,11 @@ static int kexec_walk_memblock(struct kexec_buf *kbuf,
 	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) {
diff --git a/mm/memblock.c b/mm/memblock.c
index 47a56b223141..540a35317fb0 100644
--- a/mm/memblock.c
+++ b/mm/memblock.c
@@ -979,6 +979,10 @@ static bool should_skip_region(struct memblock_type *type,
 	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;
 }
 
-- 
2.31.1


  parent reply	other threads:[~2021-09-27 15:06 UTC|newest]

Thread overview: 15+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-09-27 15:05 [PATCH v1 0/4] mm/memory_hotplug: full support for David Hildenbrand
2021-09-27 15:05 ` [PATCH v1 1/4] mm/memory_hotplug: handle memblock_add_node() failures in add_memory_resource() David Hildenbrand
2021-09-27 15:05 ` [PATCH v1 2/4] memblock: allow to specify flags with memblock_add_node() David Hildenbrand
2021-09-27 15:19   ` Geert Uytterhoeven
2021-09-28  9:38   ` Heiko Carstens
2021-09-29 16:25   ` Mike Rapoport
2021-09-29 16:30     ` David Hildenbrand
2021-09-27 15:05 ` David Hildenbrand [this message]
2021-09-29 16:39   ` [PATCH v1 3/4] memblock: add MEMBLOCK_DRIVER_MANAGED to mimic IORESOURCE_SYSRAM_DRIVER_MANAGED Mike Rapoport
2021-09-29 16:54     ` David Hildenbrand
2021-09-30 21:21       ` Mike Rapoport
2021-10-01  8:04         ` David Hildenbrand
2021-10-01 14:03           ` Mike Rapoport
2021-09-27 15:05 ` [PATCH v1 4/4] mm/memory_hotplug: indicate MEMBLOCK_DRIVER_MANAGED with IORESOURCE_SYSRAM_DRIVER_MANAGED David Hildenbrand
2021-09-27 15:07 ` [PATCH v1 0/4] mm/memory_hotplug: full support for David Hildenbrand

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