LoongArch: Set initial pte entry with PAGE_GLOBAL for kernel space

There are two pages in one TLB entry on LoongArch system. For kernel
space, it requires both two pte entries (buddies) with PAGE_GLOBAL bit
set, otherwise HW treats it as non-global tlb, there will be potential
problems if tlb entry for kernel space is not global. Such as fail to
flush kernel tlb with the function local_flush_tlb_kernel_range() which
supposed only flush tlb with global bit.

Kernel address space areas include percpu, vmalloc, vmemmap, fixmap and
kasan areas. For these areas both two consecutive page table entries
should be enabled with PAGE_GLOBAL bit. So with function set_pte() and
pte_clear(), pte buddy entry is checked and set besides its own pte
entry. However it is not atomic operation to set both two pte entries,
there is problem with test_vmalloc test case.

So function kernel_pte_init() is added to init a pte table when it is
created for kernel address space, and the default initial pte value is
PAGE_GLOBAL rather than zero at beginning. Then only its own pte entry
need update with function set_pte() and pte_clear(), nothing to do with
the pte buddy entry.

Signed-off-by: Bibo Mao <maobibo@loongson.cn>
Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>

2 files changed, 12 insertions, 1 deletions

diff --git a/mm/kasan/init.c b/mm/kasan/init.c
index 89895f38f722..ac607c306292 100644
--- a/mm/kasan/init.c
+++ b/mm/kasan/init.c
@@ -106,6 +106,10 @@ static void __ref zero_pte_populate(pmd_t *pmd, unsigned long addr,
 	}
 }
 
+void __weak __meminit kernel_pte_init(void *addr)
+{
+}
+
 static int __ref zero_pmd_populate(pud_t *pud, unsigned long addr,
 				unsigned long end)
 {
@@ -126,8 +130,10 @@ static int __ref zero_pmd_populate(pud_t *pud, unsigned long addr,
 
 			if (slab_is_available())
 				p = pte_alloc_one_kernel(&init_mm);
-			else
+			else {
 				p = early_alloc(PAGE_SIZE, NUMA_NO_NODE);
+				kernel_pte_init(p);
+			}
 			if (!p)
 				return -ENOMEM;
 
diff --git a/mm/sparse-vmemmap.c b/mm/sparse-vmemmap.c
index edcc7a6b0f6f..c0388b2e959d 100644
--- a/mm/sparse-vmemmap.c
+++ b/mm/sparse-vmemmap.c
@@ -184,6 +184,10 @@ static void * __meminit vmemmap_alloc_block_zero(unsigned long size, int node)
 	return p;
 }
 
+void __weak __meminit kernel_pte_init(void *addr)
+{
+}
+
 pmd_t * __meminit vmemmap_pmd_populate(pud_t *pud, unsigned long addr, int node)
 {
 	pmd_t *pmd = pmd_offset(pud, addr);
@@ -191,6 +195,7 @@ pmd_t * __meminit vmemmap_pmd_populate(pud_t *pud, unsigned long addr, int node)
 		void *p = vmemmap_alloc_block_zero(PAGE_SIZE, node);
 		if (!p)
 			return NULL;
+		kernel_pte_init(p);
 		pmd_populate_kernel(&init_mm, pmd, p);
 	}
 	return pmd;