Re: [POC][RFC][PATCH 0/2] pstore/mm/x86: Add wildcard memmap to map pstore consistently

Steven Rostedt
2024-04-12T17:22:47Z

On Fri, 12 Apr 2024 09:17:18 -0300
"Guilherme G. Piccoli" <gpiccoli@igalia.com> wrote:

> Thanks Steve, seems a good idea. With that, I could test on kdumpst (the
> tool used on Steam Deck), since it relies on modular pstore/ram.

Something like this could work.

-- Steve

diff --git a/arch/x86/kernel/e820.c b/arch/x86/kernel/e820.c
index a8831ef30c73..878aee8b2399 100644
--- a/arch/x86/kernel/e820.c
+++ b/arch/x86/kernel/e820.c
@@ -16,6 +16,7 @@
#include <linux/firmware-map.h>
#include <linux/sort.h>
#include <linux/memory_hotplug.h>
+#include <linux/mm.h>

#include <asm/e820/api.h>
#include <asm/setup.h>
@@ -64,61 +65,6 @@ struct e820_table *e820_table __refdata = &e820_table_init;
struct e820_table *e820_table_kexec __refdata = &e820_table_kexec_init;
struct e820_table *e820_table_firmware __refdata = &e820_table_firmware_init;

-/* For wildcard memory requests, have a table to find them later */
-#define E820_MAX_MAPS 8
-#define E820_MAP_NAME_SIZE 16
-struct e820_mmap_map {
- char name[E820_MAP_NAME_SIZE];
- u64 start;
- u64 size;
-};
-static struct e820_mmap_map e820_mmap_list[E820_MAX_MAPS] __initdata;
-static int e820_mmap_size __initdata;
-
-/* Add wildcard region with a lookup name */
-static int __init e820_add_mmap(u64 start, u64 size, const char *name)
-{
- struct e820_mmap_map *map;
-
- if (!name || !name[0] || strlen(name) >= E820_MAP_NAME_SIZE)
- return -EINVAL;
-
- if (e820_mmap_size >= E820_MAX_MAPS)
- return -1;
-
- map = &e820_mmap_list[e820_mmap_size++];
- map->start = start;
- map->size = size;
- strcpy(map->name, name);
- return 0;
-}
-
-/**
- * memmap_named - Find a wildcard region with a given name
- * @name: The name that is attached to a wildcard region
- * @start: If found, holds the start address
- * @size: If found, holds the size of the address.
- *
- * Returns: 1 if found or 0 if not found.
- */
-int __init memmap_named(const char *name, u64 *start, u64 *size)
-{
- struct e820_mmap_map *map;
- int i;
-
- for (i = 0; i < e820_mmap_size; i++) {
- map = &e820_mmap_list[i];
- if (!map->size)
- continue;
- if (strcmp(name, map->name) == 0) {
- *start = map->start;
- *size = map->size;
- return 1;
- }
- }
- return 0;
-}
-
/* For PCI or other memory-mapped resources */
unsigned long pci_mem_start = 0xaeedbabe;
#ifdef CONFIG_PCI
@@ -1024,6 +970,8 @@ static int __init parse_memmap_one(char *p)
e820__range_add(start_at, mem_size, E820_TYPE_RESERVED);
} else if (*p == '*') {
u64 align;
+ int ret;
+
/* Followed by alignment and ':' then the name */
align = memparse(p+1, &p);
start_at = e820__region(mem_size, align);
@@ -1032,9 +980,10 @@ static int __init parse_memmap_one(char *p)
if (*p != ':')
return -EINVAL;
p++;
- e820_add_mmap(start_at, mem_size, p);
+ ret = memmap_add(start_at, mem_size, p);
p += strlen(p);
- e820__range_add(start_at, mem_size, E820_TYPE_RESERVED);
+ if (!ret)
+ e820__range_add(start_at, mem_size, E820_TYPE_RESERVED);
} else if (*p == '!') {
start_at = memparse(p+1, &p);
e820__range_add(start_at, mem_size, E820_TYPE_PRAM);
diff --git a/fs/pstore/ram.c b/fs/pstore/ram.c
index c200388399fb..22d2e2731dc2 100644
--- a/fs/pstore/ram.c
+++ b/fs/pstore/ram.c
@@ -919,7 +919,6 @@ static void __init ramoops_register_dummy(void)
{
struct ramoops_platform_data pdata;

-#ifndef MODULE
/* Only allowed when builtin */
if (mem_name) {
u64 start;
@@ -930,7 +929,6 @@ static void __init ramoops_register_dummy(void)
mem_size = size;
}
}
-#endif

/*
* Prepare a dummy platform data structure to carry the module
diff --git a/include/linux/mm.h b/include/linux/mm.h
index cf9b34454c6f..6ce1c6929d1f 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -4203,5 +4203,6 @@ static inline bool pfn_is_unaccepted_memory(unsigned long pfn)
}

int memmap_named(const char *name, u64 *start, u64 *size);
+int memmap_add(long start, long size, const char *name);

#endif /* _LINUX_MM_H */
diff --git a/mm/memory.c b/mm/memory.c
index 7a29f17df7c1..fe054e1bb678 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -120,12 +120,6 @@ static bool vmf_orig_pte_uffd_wp(struct vm_fault *vmf)
return pte_marker_uffd_wp(vmf->orig_pte);
}

-int __init __weak memmap_named(const char *name, u64 *start, u64 *size)
-{
- pr_info("Kernel command line: memmap=nn*align:name not supported on this kernel");
- /* zero means not found */
- return 0;
-}

/*
* A number of key systems in x86 including ioremap() rely on the assumption
diff --git a/mm/mm_init.c b/mm/mm_init.c
index 549e76af8f82..e5b729b83fdc 100644
--- a/mm/mm_init.c
+++ b/mm/mm_init.c
@@ -154,6 +154,77 @@ static __init int set_mminit_loglevel(char *str)
early_param("mminit_loglevel", set_mminit_loglevel);
#endif /* CONFIG_DEBUG_MEMORY_INIT */

+/* For wildcard memory requests, have a table to find them later */
+#define MAX_MAPS 8
+#define MAP_NAME_SIZE 16
+struct mmap_map {
+ char name[MAP_NAME_SIZE];
+ long start;
+ long size;
+};
+static struct mmap_map early_mmap_list[MAX_MAPS] __initdata;
+static int early_mmap_size __initdata;
+static struct mmap_map *mmap_list;
+
+/* Add wildcard region with a lookup name */
+int memmap_add(long start, long size, const char *name)
+{
+ struct mmap_map *map;
+
+ if (!name || !name[0] || strlen(name) >= MAP_NAME_SIZE)
+ return -EINVAL;
+
+ if (early_mmap_size >= MAX_MAPS)
+ return -1;
+
+ map = &early_mmap_list[early_mmap_size++];
+ map->start = start;
+ map->size = size;
+ strcpy(map->name, name);
+ return 0;
+}
+
+static void __init memmap_copy(void)
+{
+ if (!early_mmap_size)
+ return;
+
+ mmap_list = kcalloc(early_mmap_size + 1, sizeof(mmap_list), GFP_KERNEL);
+ if (!mmap_list)
+ return;
+
+ for (int i = 0; i < early_mmap_size; i++)
+ mmap_list[i] = early_mmap_list[i];
+}
+
+/**
+ * memmap_named - Find a wildcard region with a given name
+ * @name: The name that is attached to a wildcard region
+ * @start: If found, holds the start address
+ * @size: If found, holds the size of the address.
+ *
+ * Returns: 1 if found or 0 if not found.
+ */
+int memmap_named(const char *name, u64 *start, u64 *size)
+{
+ struct mmap_map *map;
+
+ if (!mmap_list)
+ return 0;
+
+ for (int i = 0; mmap_list[i].name[0]; i++) {
+ map = &mmap_list[i];
+ if (!map->size)
+ continue;
+ if (strcmp(name, map->name) == 0) {
+ *start = map->start;
+ *size = map->size;
+ return 1;
+ }
+ }
+ return 0;
+}
+
struct kobject *mm_kobj;

#ifdef CONFIG_SMP
@@ -2793,4 +2864,5 @@ void __init mm_core_init(void)
pti_init();
kmsan_init_runtime();
mm_cache_init();
+ memmap_copy();
}