Add architecture-independent helpers to allow individual architectures
to work around their own limitations when updating vmemmap.
Specifically, the current remap workflow requires break-before-make
(BBM) on arm64. By overriding the default helpers later in this
series, arm64 will be able to support the current HVO implementation.
Signed-off-by: Yu Zhao <yuzhao@xxxxxxxxxx>
---
include/linux/mm_types.h | 7 +++
mm/hugetlb_vmemmap.c | 99 ++++++++++++++++++++++++++++++++++------
2 files changed, 92 insertions(+), 14 deletions(-)
diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h
index 6e3bdf8e38bc..0f3ae6e173f6 100644
--- a/include/linux/mm_types.h
+++ b/include/linux/mm_types.h
@@ -1499,4 +1499,11 @@ enum {
/* See also internal only FOLL flags in mm/internal.h */
};
+/* Skip the TLB flush when we split the PMD */
+#define VMEMMAP_SPLIT_NO_TLB_FLUSH BIT(0)
+/* Skip the TLB flush when we remap the PTE */
+#define VMEMMAP_REMAP_NO_TLB_FLUSH BIT(1)
+/* synchronize_rcu() to avoid writes from page_ref_add_unless() */
+#define VMEMMAP_SYNCHRONIZE_RCU BIT(2)
+
#endif /* _LINUX_MM_TYPES_H */
diff --git a/mm/hugetlb_vmemmap.c b/mm/hugetlb_vmemmap.c
index 46befab48d41..e50a196399f5 100644
--- a/mm/hugetlb_vmemmap.c
+++ b/mm/hugetlb_vmemmap.c
@@ -38,16 +38,56 @@ struct vmemmap_remap_walk {
struct page *reuse_page;
unsigned long reuse_addr;
struct list_head *vmemmap_pages;
-
-/* Skip the TLB flush when we split the PMD */
-#define VMEMMAP_SPLIT_NO_TLB_FLUSH BIT(0)
-/* Skip the TLB flush when we remap the PTE */
-#define VMEMMAP_REMAP_NO_TLB_FLUSH BIT(1)
-/* synchronize_rcu() to avoid writes from page_ref_add_unless() */
-#define VMEMMAP_SYNCHRONIZE_RCU BIT(2)
unsigned long flags;
};
+#ifndef VMEMMAP_ARCH_TLB_FLUSH_FLAGS
+#define VMEMMAP_ARCH_TLB_FLUSH_FLAGS 0
+#endif
+
+#ifndef vmemmap_update_supported
+static bool vmemmap_update_supported(void)
+{
+ return true;
+}
+#endif
+
+#ifndef vmemmap_update_lock
+static void vmemmap_update_lock(void)
+{
+}
+#endif
+
+#ifndef vmemmap_update_unlock
+static void vmemmap_update_unlock(void)
+{
+}
+#endif
+
+#ifndef vmemmap_update_pte_range_start
+static void vmemmap_update_pte_range_start(pte_t *pte, unsigned long start, unsigned long end)
+{
+}
+#endif
+
+#ifndef vmemmap_update_pte_range_end
+static void vmemmap_update_pte_range_end(void)
+{
+}
+#endif
+
+#ifndef vmemmap_update_pmd_range_start
+static void vmemmap_update_pmd_range_start(pmd_t *pmd, unsigned long start, unsigned long end)
+{
+}
+#endif
+
+#ifndef vmemmap_update_pmd_range_end
+static void vmemmap_update_pmd_range_end(void)
+{
+}
+#endif
+
static int vmemmap_split_pmd(pmd_t *pmd, struct page *head, unsigned long start,
struct vmemmap_remap_walk *walk)
{
@@ -83,7 +123,9 @@ static int vmemmap_split_pmd(pmd_t *pmd, struct page *head, unsigned long start,
/* Make pte visible before pmd. See comment in pmd_install(). */
smp_wmb();
+ vmemmap_update_pmd_range_start(pmd, start, start + PMD_SIZE);
pmd_populate_kernel(&init_mm, pmd, pgtable);
+ vmemmap_update_pmd_range_end();
if (!(walk->flags & VMEMMAP_SPLIT_NO_TLB_FLUSH))
flush_tlb_kernel_range(start, start + PMD_SIZE);
} else {
@@ -164,10 +206,12 @@ static int vmemmap_remap_range(unsigned long start, unsigned long end,
VM_BUG_ON(!PAGE_ALIGNED(start | end));
+ vmemmap_update_lock();
mmap_read_lock(&init_mm);
ret = walk_page_range_novma(&init_mm, start, end, &vmemmap_remap_ops,
NULL, walk);
mmap_read_unlock(&init_mm);
+ vmemmap_update_unlock();
if (ret)
return ret;
@@ -228,6 +272,8 @@ static void vmemmap_remap_pte_range(pte_t *pte, unsigned long start, unsigned lo
smp_wmb();
}
+ vmemmap_update_pte_range_start(pte, start, end);
+
for (i = 0; i < nr_pages; i++) {
pte_t val;
@@ -242,6 +288,8 @@ static void vmemmap_remap_pte_range(pte_t *pte, unsigned long start, unsigned lo
set_pte_at(&init_mm, start + PAGE_SIZE * i, pte + i, val);
}
+
+ vmemmap_update_pte_range_end();
}
/*
@@ -287,6 +335,8 @@ static void vmemmap_restore_pte_range(pte_t *pte, unsigned long start, unsigned
*/
smp_wmb();
+ vmemmap_update_pte_range_start(pte, start, end);
+
for (i = 0; i < nr_pages; i++) {
pte_t val;
@@ -296,6 +346,8 @@ static void vmemmap_restore_pte_range(pte_t *pte, unsigned long start, unsigned
val = mk_pte(page, PAGE_KERNEL);
set_pte_at(&init_mm, start + PAGE_SIZE * i, pte + i, val);
}
+
+ vmemmap_update_pte_range_end();
}
/**
@@ -513,7 +565,8 @@ static int __hugetlb_vmemmap_restore_folio(const struct hstate *h,
*/
int hugetlb_vmemmap_restore_folio(const struct hstate *h, struct folio *folio)
{
- return __hugetlb_vmemmap_restore_folio(h, folio, VMEMMAP_SYNCHRONIZE_RCU);
+ return __hugetlb_vmemmap_restore_folio(h, folio,
+ VMEMMAP_SYNCHRONIZE_RCU | VMEMMAP_ARCH_TLB_FLUSH_FLAGS);
}
/**
@@ -553,7 +606,7 @@ long hugetlb_vmemmap_restore_folios(const struct hstate *h,
list_move(&folio->lru, non_hvo_folios);
}
- if (restored)
+ if (restored && !(VMEMMAP_ARCH_TLB_FLUSH_FLAGS & VMEMMAP_REMAP_NO_TLB_FLUSH))
flush_tlb_all();
if (!ret)
ret = restored;
@@ -641,7 +694,8 @@ void hugetlb_vmemmap_optimize_folio(const struct hstate *h, struct folio *folio)
{
LIST_HEAD(vmemmap_pages);
- __hugetlb_vmemmap_optimize_folio(h, folio, &vmemmap_pages, VMEMMAP_SYNCHRONIZE_RCU);
+ __hugetlb_vmemmap_optimize_folio(h, folio, &vmemmap_pages,
+ VMEMMAP_SYNCHRONIZE_RCU | VMEMMAP_ARCH_TLB_FLUSH_FLAGS);
free_vmemmap_page_list(&vmemmap_pages);
}
@@ -683,7 +737,8 @@ void hugetlb_vmemmap_optimize_folios(struct hstate *h, struct list_head *folio_l
break;
}
- flush_tlb_all();
+ if (!(VMEMMAP_ARCH_TLB_FLUSH_FLAGS & VMEMMAP_SPLIT_NO_TLB_FLUSH))
+ flush_tlb_all();
list_for_each_entry(folio, folio_list, lru) {
int ret;
@@ -701,24 +756,35 @@ void hugetlb_vmemmap_optimize_folios(struct hstate *h, struct list_head *folio_l
* allowing more vmemmap remaps to occur.
*/
if (ret == -ENOMEM && !list_empty(&vmemmap_pages)) {
- flush_tlb_all();
+ if (!(VMEMMAP_ARCH_TLB_FLUSH_FLAGS & VMEMMAP_REMAP_NO_TLB_FLUSH))
+ flush_tlb_all();
free_vmemmap_page_list(&vmemmap_pages);
INIT_LIST_HEAD(&vmemmap_pages);
__hugetlb_vmemmap_optimize_folio(h, folio, &vmemmap_pages, flags);
}
}
- flush_tlb_all();
+ if (!(VMEMMAP_ARCH_TLB_FLUSH_FLAGS & VMEMMAP_REMAP_NO_TLB_FLUSH))
+ flush_tlb_all();
free_vmemmap_page_list(&vmemmap_pages);
}
+static int hugetlb_vmemmap_sysctl(const struct ctl_table *ctl, int write,
+ void *buffer, size_t *lenp, loff_t *ppos)
+{
+ if (!vmemmap_update_supported())
+ return -ENODEV;
+
+ return proc_dobool(ctl, write, buffer, lenp, ppos);
+}
+
static struct ctl_table hugetlb_vmemmap_sysctls[] = {
{
.procname = "hugetlb_optimize_vmemmap",
.data = &vmemmap_optimize_enabled,
.maxlen = sizeof(vmemmap_optimize_enabled),
.mode = 0644,
- .proc_handler = proc_dobool,
+ .proc_handler = hugetlb_vmemmap_sysctl,
},
};
@@ -729,6 +795,11 @@ static int __init hugetlb_vmemmap_init(void)
/* HUGETLB_VMEMMAP_RESERVE_SIZE should cover all used struct pages */
BUILD_BUG_ON(__NR_USED_SUBPAGE > HUGETLB_VMEMMAP_RESERVE_PAGES);
+ if (READ_ONCE(vmemmap_optimize_enabled) && !vmemmap_update_supported()) {
+ pr_warn("HugeTLB: disabling HVO due to missing support.\n");
+ WRITE_ONCE(vmemmap_optimize_enabled, false);
+ }
+
for_each_hstate(h) {
if (hugetlb_vmemmap_optimizable(h)) {
register_sysctl_init("vm", hugetlb_vmemmap_sysctls);
--
2.47.0.rc1.288.g06298d1525-goog
