s390/kasan: remove 3-level paging support

Compiling the kernel with Kasan disables automatic 3-level vs 4-level
kernel space paging selection, because the shadow memory offset has
to be known at compile time and there is no such offset which would be
acceptable for both 3 and 4-level paging. Instead S390_4_LEVEL_PAGING
option was introduced which allowed to pick how many paging levels to
use under Kasan.

With the introduction of protected virtualization, kernel memory layout
may be affected due to ultravisor secure storage limit. This adds
additional complexity into how memory layout would look like in
combination with Kasan predefined shadow memory offsets. To simplify
this make Kasan 4-level paging default and remove Kasan 3-level paging
support.

Suggested-by: Heiko Carstens <hca@linux.ibm.com>
Reviewed-by: Alexander Gordeev <agordeev@linux.ibm.com>
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>

1 files changed, 10 insertions, 42 deletions

diff --git a/arch/s390/mm/kasan_init.c b/arch/s390/mm/kasan_init.c
index 5646b39c728a..fcb2b533b235 100644
--- a/arch/s390/mm/kasan_init.c
+++ b/arch/s390/mm/kasan_init.c
@@ -123,8 +123,7 @@ static void __init kasan_early_vmemmap_populate(unsigned long address,
 			pgd_populate(&init_mm, pg_dir, p4_dir);
 		}
 
-		if (IS_ENABLED(CONFIG_KASAN_S390_4_LEVEL_PAGING) &&
-		    mode == POPULATE_SHALLOW) {
+		if (mode == POPULATE_SHALLOW) {
 			address = (address + P4D_SIZE) & P4D_MASK;
 			continue;
 		}
@@ -143,12 +142,6 @@ static void __init kasan_early_vmemmap_populate(unsigned long address,
 			p4d_populate(&init_mm, p4_dir, pu_dir);
 		}
 
-		if (!IS_ENABLED(CONFIG_KASAN_S390_4_LEVEL_PAGING) &&
-		    mode == POPULATE_SHALLOW) {
-			address = (address + PUD_SIZE) & PUD_MASK;
-			continue;
-		}
-
 		pu_dir = pud_offset(p4_dir, address);
 		if (pud_none(*pu_dir)) {
 			if (mode == POPULATE_ZERO_SHADOW &&
@@ -281,7 +274,6 @@ void __init kasan_early_init(void)
 	unsigned long shadow_alloc_size;
 	unsigned long vmax_unlimited;
 	unsigned long initrd_end;
-	unsigned long asce_type;
 	unsigned long memsize;
 	unsigned long pgt_prot = pgprot_val(PAGE_KERNEL_RO);
 	pte_t pte_z;
@@ -304,25 +296,12 @@ void __init kasan_early_init(void)
 		memsize = min(memsize, OLDMEM_SIZE);
 	memsize = min(memsize, KASAN_SHADOW_START);
 
-	if (IS_ENABLED(CONFIG_KASAN_S390_4_LEVEL_PAGING)) {
-		/* 4 level paging */
-		BUILD_BUG_ON(!IS_ALIGNED(KASAN_SHADOW_START, P4D_SIZE));
-		BUILD_BUG_ON(!IS_ALIGNED(KASAN_SHADOW_END, P4D_SIZE));
-		crst_table_init((unsigned long *)early_pg_dir,
-				_REGION2_ENTRY_EMPTY);
-		untracked_mem_end = kasan_vmax = vmax_unlimited = _REGION1_SIZE;
-		if (has_uv_sec_stor_limit())
-			kasan_vmax = min(vmax_unlimited, uv_info.max_sec_stor_addr);
-		asce_type = _ASCE_TYPE_REGION2;
-	} else {
-		/* 3 level paging */
-		BUILD_BUG_ON(!IS_ALIGNED(KASAN_SHADOW_START, PUD_SIZE));
-		BUILD_BUG_ON(!IS_ALIGNED(KASAN_SHADOW_END, PUD_SIZE));
-		crst_table_init((unsigned long *)early_pg_dir,
-				_REGION3_ENTRY_EMPTY);
-		untracked_mem_end = kasan_vmax = vmax_unlimited = _REGION2_SIZE;
-		asce_type = _ASCE_TYPE_REGION3;
-	}
+	BUILD_BUG_ON(!IS_ALIGNED(KASAN_SHADOW_START, P4D_SIZE));
+	BUILD_BUG_ON(!IS_ALIGNED(KASAN_SHADOW_END, P4D_SIZE));
+	crst_table_init((unsigned long *)early_pg_dir, _REGION2_ENTRY_EMPTY);
+	untracked_mem_end = kasan_vmax = vmax_unlimited = _REGION1_SIZE;
+	if (has_uv_sec_stor_limit())
+		kasan_vmax = min(vmax_unlimited, uv_info.max_sec_stor_addr);
 
 	/* init kasan zero shadow */
 	crst_table_init((unsigned long *)kasan_early_shadow_p4d,
@@ -408,7 +387,7 @@ void __init kasan_early_init(void)
 	pgalloc_freeable = pgalloc_pos;
 	/* populate identity mapping */
 	kasan_early_vmemmap_populate(0, memsize, POPULATE_ONE2ONE);
-	kasan_set_pgd(early_pg_dir, asce_type);
+	kasan_set_pgd(early_pg_dir, _ASCE_TYPE_REGION2);
 	kasan_enable_dat();
 	/* enable kasan */
 	init_task.kasan_depth = 0;
@@ -428,24 +407,13 @@ void __init kasan_copy_shadow(pgd_t *pg_dir)
 	pgd_t *pg_dir_dst;
 	p4d_t *p4_dir_src;
 	p4d_t *p4_dir_dst;
-	pud_t *pu_dir_src;
-	pud_t *pu_dir_dst;
 
 	pg_dir_src = pgd_offset_raw(early_pg_dir, KASAN_SHADOW_START);
 	pg_dir_dst = pgd_offset_raw(pg_dir, KASAN_SHADOW_START);
 	p4_dir_src = p4d_offset(pg_dir_src, KASAN_SHADOW_START);
 	p4_dir_dst = p4d_offset(pg_dir_dst, KASAN_SHADOW_START);
-	if (!p4d_folded(*p4_dir_src)) {
-		/* 4 level paging */
-		memcpy(p4_dir_dst, p4_dir_src,
-		       (KASAN_SHADOW_SIZE >> P4D_SHIFT) * sizeof(p4d_t));
-		return;
-	}
-	/* 3 level paging */
-	pu_dir_src = pud_offset(p4_dir_src, KASAN_SHADOW_START);
-	pu_dir_dst = pud_offset(p4_dir_dst, KASAN_SHADOW_START);
-	memcpy(pu_dir_dst, pu_dir_src,
-	       (KASAN_SHADOW_SIZE >> PUD_SHIFT) * sizeof(pud_t));
+	memcpy(p4_dir_dst, p4_dir_src,
+	       (KASAN_SHADOW_SIZE >> P4D_SHIFT) * sizeof(p4d_t));
 }
 
 void __init kasan_free_early_identity(void)