[RFC PATCH 18/18] mm: introduce kernel cmdline option "kernel_replication="
Nikita Panov
panov.nikita at huawei.com
Thu Aug 27 09:11:58 PDT 2026
The new cmdline option allows enabling/disabling
kernel replication feature.
By default, the replication feature is disabled.
This allows to set CONFIG_KERNEL_REPLICATION=y by default,
but enabling this feature is done via kernel cmdline.
Signed-off-by: Nikita Panov <panov.nikita at huawei.com>
---
.../admin-guide/kernel-parameters.txt | 7 ++
include/linux/numa_kernel_replication.h | 27 ++++++-
kernel/module/main.c | 3 +
mm/numa_kernel_replication.c | 78 ++++++++++++++++++-
mm/vmalloc.c | 2 +-
5 files changed, 113 insertions(+), 4 deletions(-)
diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index d55524e3b724..133afdd7dab5 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -3039,6 +3039,13 @@ Kernel parameters
for Movable pages. "nn[KMGTPE]", "nn%", and "mirror"
are exclusive, so you cannot specify multiple forms.
+ kernel_replication=
+ [ARM64]
+ Format: [on|off]
+ If CONFIG_KERNEL_REPLICATION is set, it allows
+ enabling/disabling the kernel replication feature
+ via cmdline. Default value is off.
+
kfence.burst= [MM,KFENCE] The number of additional successive
allocations to be attempted through KFENCE for each
sample interval.
diff --git a/include/linux/numa_kernel_replication.h b/include/linux/numa_kernel_replication.h
index 34aa063d42e6..23069ca82fa8 100644
--- a/include/linux/numa_kernel_replication.h
+++ b/include/linux/numa_kernel_replication.h
@@ -18,8 +18,31 @@ extern nodemask_t replica_nodes;
nid != MAX_NUMNODES; \
nid = next_node(nid, replica_nodes))
-#define this_node_pgd(mm) ((mm)->pgd_numa[numa_node_id()])
-#define per_node_pgd(mm, nid) ((mm)->pgd_numa[nid])
+bool is_text_replicated(void);
+
+static inline pgd_t *this_node_pgd(struct mm_struct *mm)
+{
+ if (is_text_replicated())
+ return mm->pgd_numa[numa_node_id()];
+ else
+ return mm->pgd;
+}
+
+static inline pgd_t *per_node_pgd(struct mm_struct *mm, int nid)
+{
+ if (is_text_replicated())
+ return mm->pgd_numa[nid];
+ else
+ return mm->pgd;
+}
+
+static inline pgd_t **per_node_pgd_ptr(struct mm_struct *mm, int nid)
+{
+ if (is_text_replicated())
+ return &mm->pgd_numa[nid];
+ else
+ return &mm->pgd;
+}
static inline bool numa_addr_has_replica(const void *addr)
{
diff --git a/kernel/module/main.c b/kernel/module/main.c
index d5c8f041be48..25c8816588ce 100644
--- a/kernel/module/main.c
+++ b/kernel/module/main.c
@@ -1346,6 +1346,9 @@ static void module_replicate_sections(struct module *mod)
{
int i;
+ if (!is_text_replicated())
+ return;
+
for (i = 0; i < ARRAY_SIZE(sections_to_replicate); i++)
module_replicate(mod->mem[sections_to_replicate[i]].base);
}
diff --git a/mm/numa_kernel_replication.c b/mm/numa_kernel_replication.c
index b1c5cd2a1fa1..c8c3424fa20c 100644
--- a/mm/numa_kernel_replication.c
+++ b/mm/numa_kernel_replication.c
@@ -64,6 +64,8 @@ static unsigned int master_node = INT_MAX;
*/
static int node_to_memory_node[MAX_NUMNODES];
+static bool kernel_replication_enabled;
+
static bool pgtables_extra;
static DEFINE_SPINLOCK(debugfs_lock);
@@ -253,6 +255,9 @@ static void dump_pgtables(struct mm_struct *mm,
start = start & PAGE_MASK;
end = (end & PAGE_MASK) - 1 + PAGE_SIZE;
+ if (!mm->pgd_numa)
+ return;
+
replication_log(data,
"----PER-NUMA NODE KERNEL REPLICATION ENABLED----\n");
@@ -619,6 +624,18 @@ static void replicate_pgtables(void)
}
}
+static void __init numa_replicate_kernel_text_disabled(void)
+{
+ int nid;
+
+ init_mm.pgd_numa = (pgd_t **)kmalloc(sizeof(pgd_t *) * MAX_NUMNODES, GFP_PGTABLE_KERNEL);
+ BUG_ON(!init_mm.pgd_numa);
+ for_each_online_node(nid) {
+ init_mm.pgd_numa[nid] = init_mm.pgd;
+ }
+}
+
+
/*
* Kernel text replication includes two steps:
* 1. page tables replication for init_mm
@@ -636,6 +653,11 @@ void __init numa_replicate_kernel_text(void)
{
int nid;
+ if (!kernel_replication_enabled) {
+ numa_replicate_kernel_text_disabled();
+ return;
+ }
+
replicate_pgtables();
for_each_memory_node(nid) {
@@ -653,6 +675,10 @@ void numa_replicate_kernel_rodata(void)
{
int nid;
+ if (!kernel_replication_enabled) {
+ return;
+ }
+
for_each_memory_node(nid) {
if (nid == master_node)
continue;
@@ -664,7 +690,7 @@ void numa_replicate_kernel_rodata(void)
void numa_setup_pgd(void)
{
- numa_load_replicated_pgd(init_mm.pgd_numa[numa_node_id()]);
+ numa_load_replicated_pgd(this_node_pgd(&init_mm));
}
void __init_or_module *numa_get_replica(void *vaddr, int nid)
@@ -679,8 +705,48 @@ void __init_or_module *numa_get_replica(void *vaddr, int nid)
return node_desc[nid].text_vaddr + offset;
}
+static int __init setup_kernel_replication(char *str)
+{
+ int ret = 0;
+
+ if (!str)
+ goto out;
+ if (!strcmp(str, "on")) {
+ kernel_replication_enabled = true;
+ pr_info("Kernel replication enabled via cmdline\n");
+ ret = 1;
+ } else if (!strcmp(str, "off")) {
+ kernel_replication_enabled = false;
+ pr_info("Kernel replication disabled via cmdline\n");
+ ret = 1;
+ }
+out:
+ if (!ret)
+ pr_warn("kernel_replication= cannot parse, ignored\n");
+ return ret;
+}
+__setup("kernel_replication=", setup_kernel_replication);
+
+
nodemask_t __ro_after_init replica_nodes = { { [0] = 1UL } };
+/*
+ * Let us pretend, that we have only single node fore replicas.
+ * Do not replicate anything.
+ */
+static void __init numa_replication_init_disabled(void)
+{
+ int nid;
+
+ __node_set(0, &replica_nodes);
+ for_each_online_node(nid) {
+ node_to_memory_node[nid] = 0;
+ }
+
+ node_desc[0].text_vaddr = lm_alias((void *)KERNEL_TEXT_START);
+ node_desc[0].rodata_vaddr = lm_alias((void *)KERNEL_RODATA_START);
+}
+
void __init numa_replication_init(void)
{
int nid;
@@ -693,6 +759,16 @@ void __init numa_replication_init(void)
#endif
nodes_clear(replica_nodes);
+ if (kernel_replication_enabled)
+ pr_info("WARNING! WARNING! WARNING! Kernel replication enabled WARNING! WARNING! WARNING!\n");
+ else
+ pr_info("Kernel replication disabled\n");
+
+ if (!kernel_replication_enabled) {
+ numa_replication_init_disabled();
+ return;
+ }
+
for_each_node_state(nid, N_MEMORY) {
__node_set(nid, &replica_nodes);
}
diff --git a/mm/vmalloc.c b/mm/vmalloc.c
index da6facf64db8..532298ab4263 100644
--- a/mm/vmalloc.c
+++ b/mm/vmalloc.c
@@ -4422,7 +4422,7 @@ int __vmalloc_node_replicate_range(const void *addr, gfp_t gfp_mask,
for (i = 0; i < area->nr_pages; i++)
list_add(&pages[i]->lru, &area->pages[i]->lru);
- __vunmap_range_noflush_pgd(init_mm.pgd_numa[node],
+ __vunmap_range_noflush_pgd(per_node_pgd(&init_mm, node),
area_start, area_end);
/*
--
2.34.1
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