[PATCHv2 06/10] x86/mm: Handle boot-time paging mode switching at early boot

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This patch adds detection of 5-level paging at boot-time and adjusts
virtual memory layout and folds p4d page table layer if needed.

Signed-off-by: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx>
---
 arch/x86/boot/compressed/kaslr.c        | 13 +++++--
 arch/x86/entry/entry_64.S               | 12 +++++++
 arch/x86/include/asm/page_64_types.h    | 13 +++----
 arch/x86/include/asm/pgtable_64_types.h | 35 +++++++++++--------
 arch/x86/include/asm/processor.h        |  2 +-
 arch/x86/include/asm/sparsemem.h        | 12 ++++---
 arch/x86/kernel/head64.c                | 62 +++++++++++++++++++++++++--------
 arch/x86/kernel/head_64.S               | 18 ++++++----
 arch/x86/mm/dump_pagetables.c           |  8 +++--
 arch/x86/mm/kaslr.c                     | 13 ++++---
 10 files changed, 132 insertions(+), 56 deletions(-)

diff --git a/arch/x86/boot/compressed/kaslr.c b/arch/x86/boot/compressed/kaslr.c
index b742b18cc10b..a0a8fefb6c0d 100644
--- a/arch/x86/boot/compressed/kaslr.c
+++ b/arch/x86/boot/compressed/kaslr.c
@@ -44,8 +44,9 @@
 #include <linux/decompress/mm.h>
 
 #ifdef CONFIG_X86_5LEVEL
-unsigned int pgdir_shift = 48;
-unsigned int ptrs_per_p4d = 512;
+unsigned int p4d_folded = 1;
+unsigned int pgdir_shift = 39;
+unsigned int ptrs_per_p4d = 1;
 #endif
 
 extern unsigned long get_cmd_line_ptr(void);
@@ -635,6 +636,14 @@ void choose_random_location(unsigned long input,
 		return;
 	}
 
+#ifdef CONFIG_X86_5LEVEL
+	if (__read_cr4() & X86_CR4_LA57) {
+		p4d_folded = 0;
+		pgdir_shift = 48;
+		ptrs_per_p4d = 512;
+	}
+#endif
+
 	boot_params->hdr.loadflags |= KASLR_FLAG;
 
 	/* Prepare to add new identity pagetables on demand. */
diff --git a/arch/x86/entry/entry_64.S b/arch/x86/entry/entry_64.S
index a9a8027a6c0e..66d7a4685e1f 100644
--- a/arch/x86/entry/entry_64.S
+++ b/arch/x86/entry/entry_64.S
@@ -268,8 +268,20 @@ return_from_SYSCALL_64:
 	 * Change top bits to match most significant bit (47th or 56th bit
 	 * depending on paging mode) in the address.
 	 */
+#ifdef CONFIG_X86_5LEVEL
+	testl	$1, p4d_folded(%rip)
+	jnz	1f
+	shl	$(64 - 57), %rcx
+	sar	$(64 - 57), %rcx
+	jmp	2f
+1:
+	shl	$(64 - 48), %rcx
+	sar	$(64 - 48), %rcx
+2:
+#else
 	shl	$(64 - (__VIRTUAL_MASK_SHIFT+1)), %rcx
 	sar	$(64 - (__VIRTUAL_MASK_SHIFT+1)), %rcx
+#endif
 
 	/* If this changed %rcx, it was not canonical */
 	cmpq	%rcx, %r11
diff --git a/arch/x86/include/asm/page_64_types.h b/arch/x86/include/asm/page_64_types.h
index 0126d6bc2eb1..26056ef366b8 100644
--- a/arch/x86/include/asm/page_64_types.h
+++ b/arch/x86/include/asm/page_64_types.h
@@ -36,24 +36,21 @@
  * hypervisor to fit.  Choosing 16 slots here is arbitrary, but it's
  * what Xen requires.
  */
-#ifdef CONFIG_X86_5LEVEL
-#define __PAGE_OFFSET_BASE      _AC(0xff10000000000000, UL)
-#else
-#define __PAGE_OFFSET_BASE      _AC(0xffff880000000000, UL)
-#endif
+#define __PAGE_OFFSET_BASE57	_AC(0xff10000000000000, UL)
+#define __PAGE_OFFSET_BASE48	_AC(0xffff880000000000, UL)
 
 #if defined(CONFIG_RANDOMIZE_MEMORY) || defined(CONFIG_X86_5LEVEL)
 #define __PAGE_OFFSET           page_offset_base
 #else
-#define __PAGE_OFFSET           __PAGE_OFFSET_BASE
+#define __PAGE_OFFSET           __PAGE_OFFSET_BASE48
 #endif /* CONFIG_RANDOMIZE_MEMORY */
 
 #define __START_KERNEL_map	_AC(0xffffffff80000000, UL)
 
 /* See Documentation/x86/x86_64/mm.txt for a description of the memory map. */
 #ifdef CONFIG_X86_5LEVEL
-#define __PHYSICAL_MASK_SHIFT	52
-#define __VIRTUAL_MASK_SHIFT	56
+#define __PHYSICAL_MASK_SHIFT	(p4d_folded ? 52 : 46)
+#define __VIRTUAL_MASK_SHIFT	(p4d_folded ? 47 : 56)
 #else
 #define __PHYSICAL_MASK_SHIFT	46
 #define __VIRTUAL_MASK_SHIFT	47
diff --git a/arch/x86/include/asm/pgtable_64_types.h b/arch/x86/include/asm/pgtable_64_types.h
index a5338b0936ad..57718303805e 100644
--- a/arch/x86/include/asm/pgtable_64_types.h
+++ b/arch/x86/include/asm/pgtable_64_types.h
@@ -20,7 +20,7 @@ typedef unsigned long	pgprotval_t;
 typedef struct { pteval_t pte; } pte_t;
 
 #ifdef CONFIG_X86_5LEVEL
-#define p4d_folded 0
+extern unsigned int p4d_folded;
 #else
 #define p4d_folded 1
 #endif
@@ -86,24 +86,31 @@ extern unsigned int ptrs_per_p4d;
 #define PGDIR_MASK	(~(PGDIR_SIZE - 1))
 
 /* See Documentation/x86/x86_64/mm.txt for a description of the memory map. */
-#define MAXMEM		_AC(__AC(1, UL) << MAX_PHYSMEM_BITS, UL)
-#ifdef CONFIG_X86_5LEVEL
-#define VMALLOC_SIZE_TB _AC(16384, UL)
-#define __VMALLOC_BASE	_AC(0xff92000000000000, UL)
-#define __VMEMMAP_BASE	_AC(0xffd4000000000000, UL)
-#else
-#define VMALLOC_SIZE_TB	_AC(32, UL)
-#define __VMALLOC_BASE	_AC(0xffffc90000000000, UL)
-#define __VMEMMAP_BASE	_AC(0xffffea0000000000, UL)
-#endif
+#define MAXMEM		(1UL << (p4d_folded ? MAX_PHYSMEM_BITS48 : MAX_PHYSMEM_BITS57))
+
+#ifndef __ASSEMBLY__
+#define __VMALLOC_BASE48	0xffffc90000000000
+#define __VMALLOC_BASE57	0xff92000000000000
+
+#define VMALLOC_SIZE_TB48	32UL
+#define VMALLOC_SIZE_TB57	16384UL
+
+#define __VMEMMAP_BASE48	0xffffea0000000000
+#define __VMEMMAP_BASE57	0xffd4000000000000
+
 #if defined(CONFIG_RANDOMIZE_MEMORY) || defined(CONFIG_X86_5LEVEL)
 #define VMALLOC_START	vmalloc_base
+#define VMALLOC_SIZE_TB	(!p4d_folded ? VMALLOC_SIZE_TB57 : VMALLOC_SIZE_TB48)
 #define VMEMMAP_START	vmemmap_base
 #else
-#define VMALLOC_START	__VMALLOC_BASE
-#define VMEMMAP_START	__VMEMMAP_BASE
+#define VMALLOC_START	__VMALLOC_BASE48
+#define VMALLOC_SIZE_TB	VMALLOC_SIZE_TB48
+#define VMEMMAP_START	__VMEMMAP_BASE48
 #endif /* CONFIG_RANDOMIZE_MEMORY */
-#define VMALLOC_END	(VMALLOC_START + _AC((VMALLOC_SIZE_TB << 40) - 1, UL))
+
+#define VMALLOC_END	(VMALLOC_START + (VMALLOC_SIZE_TB << 40) - 1)
+#endif
+
 #define MODULES_VADDR    (__START_KERNEL_map + KERNEL_IMAGE_SIZE)
 /* The module sections ends with the start of the fixmap */
 #define MODULES_END   __fix_to_virt(__end_of_fixed_addresses + 1)
diff --git a/arch/x86/include/asm/processor.h b/arch/x86/include/asm/processor.h
index 06d4dd8aca5d..2c331224e4b2 100644
--- a/arch/x86/include/asm/processor.h
+++ b/arch/x86/include/asm/processor.h
@@ -862,7 +862,7 @@ static inline void spin_lock_prefetch(const void *x)
 					IA32_PAGE_OFFSET : TASK_SIZE_MAX)
 
 #define STACK_TOP		TASK_SIZE_LOW
-#define STACK_TOP_MAX		TASK_SIZE_MAX
+#define STACK_TOP_MAX		(!p4d_folded ? TASK_SIZE_MAX : DEFAULT_MAP_WINDOW)
 
 #define INIT_THREAD  {						\
 	.sp0			= TOP_OF_INIT_STACK,		\
diff --git a/arch/x86/include/asm/sparsemem.h b/arch/x86/include/asm/sparsemem.h
index 1f5bee2c202f..719ac32f8eb5 100644
--- a/arch/x86/include/asm/sparsemem.h
+++ b/arch/x86/include/asm/sparsemem.h
@@ -26,12 +26,16 @@
 # endif
 #else /* CONFIG_X86_32 */
 # define SECTION_SIZE_BITS	27 /* matt - 128 is convenient right now */
+# define MAX_PHYSADDR_BITS48	44
+# define MAX_PHYSADDR_BITS57	52
+# define MAX_PHYSMEM_BITS48	46
+# define MAX_PHYSMEM_BITS57	52
 # ifdef CONFIG_X86_5LEVEL
-#  define MAX_PHYSADDR_BITS	52
-#  define MAX_PHYSMEM_BITS	52
+#  define MAX_PHYSADDR_BITS	MAX_PHYSADDR_BITS57
+#  define MAX_PHYSMEM_BITS	MAX_PHYSMEM_BITS57
 # else
-#  define MAX_PHYSADDR_BITS	44
-#  define MAX_PHYSMEM_BITS	46
+#  define MAX_PHYSADDR_BITS	MAX_PHYSADDR_BITS48
+#  define MAX_PHYSMEM_BITS	MAX_PHYSMEM_BITS48
 # endif
 #endif
 
diff --git a/arch/x86/kernel/head64.c b/arch/x86/kernel/head64.c
index e432c5947459..4d06df5f317f 100644
--- a/arch/x86/kernel/head64.c
+++ b/arch/x86/kernel/head64.c
@@ -39,20 +39,18 @@ static unsigned int __initdata next_early_pgt;
 pmdval_t early_pmd_flags = __PAGE_KERNEL_LARGE & ~(_PAGE_GLOBAL | _PAGE_NX);
 
 #ifdef CONFIG_X86_5LEVEL
-unsigned int pgdir_shift = 48;
+unsigned int pgdir_shift = 39;
 EXPORT_SYMBOL(pgdir_shift);
-unsigned int ptrs_per_p4d = 512;
+unsigned int ptrs_per_p4d = 1;
 EXPORT_SYMBOL(ptrs_per_p4d);
 #endif
 
-#if defined(CONFIG_RANDOMIZE_MEMORY) || defined(CONFIG_X86_5LEVEL)
-unsigned long page_offset_base = __PAGE_OFFSET_BASE;
+unsigned long page_offset_base = __PAGE_OFFSET_BASE48;
 EXPORT_SYMBOL(page_offset_base);
-unsigned long vmalloc_base = __VMALLOC_BASE;
+unsigned long vmalloc_base = __VMALLOC_BASE48;
 EXPORT_SYMBOL(vmalloc_base);
-unsigned long vmemmap_base = __VMEMMAP_BASE;
+unsigned long vmemmap_base = __VMEMMAP_BASE48;
 EXPORT_SYMBOL(vmemmap_base);
-#endif
 
 #define __head	__section(.head.text)
 
@@ -61,6 +59,36 @@ static void __head *fixup_pointer(void *ptr, unsigned long physaddr)
 	return ptr - (void *)_text + (void *)physaddr;
 }
 
+static unsigned long __head *fixup_long(void *ptr, unsigned long physaddr)
+{
+	return fixup_pointer(ptr, physaddr);
+}
+
+#ifdef CONFIG_X86_5LEVEL
+static unsigned int __head *fixup_int(void *ptr, unsigned long physaddr)
+{
+	return fixup_pointer(ptr, physaddr);
+}
+
+static void __head check_la57_support(unsigned long physaddr)
+{
+	if (native_cpuid_eax(0) < 7)
+		return;
+
+	if (!(native_cpuid_ecx(7) & (1 << (X86_FEATURE_LA57 & 31))))
+		return;
+
+	*fixup_int(&p4d_folded, physaddr) = 0;
+	*fixup_int(&pgdir_shift, physaddr) = 48;
+	*fixup_int(&ptrs_per_p4d, physaddr) = 512;
+	*fixup_long(&page_offset_base, physaddr) = __PAGE_OFFSET_BASE57;
+	*fixup_long(&vmalloc_base, physaddr) = __VMALLOC_BASE57;
+	*fixup_long(&vmemmap_base, physaddr) = __VMEMMAP_BASE57;
+}
+#else
+static void __head check_la57_support(unsigned long physaddr) {}
+#endif
+
 void __head __startup_64(unsigned long physaddr)
 {
 	unsigned long load_delta, *p;
@@ -70,6 +98,8 @@ void __head __startup_64(unsigned long physaddr)
 	pmdval_t *pmd, pmd_entry;
 	int i;
 
+	check_la57_support(physaddr);
+
 	/* Is the address too large? */
 	if (physaddr >> MAX_PHYSMEM_BITS)
 		for (;;);
@@ -87,9 +117,14 @@ void __head __startup_64(unsigned long physaddr)
 	/* Fixup the physical addresses in the page table */
 
 	pgd = fixup_pointer(&early_top_pgt, physaddr);
-	pgd[pgd_index(__START_KERNEL_map)] += load_delta;
-
-	if (IS_ENABLED(CONFIG_X86_5LEVEL)) {
+	p = pgd + pgd_index(__START_KERNEL_map);
+	if (p4d_folded)
+		*p = (unsigned long)level3_kernel_pgt;
+	else
+		*p = (unsigned long)level4_kernel_pgt;
+	*p += _PAGE_TABLE - __START_KERNEL_map + load_delta;
+
+	if (!p4d_folded) {
 		p4d = fixup_pointer(&level4_kernel_pgt, physaddr);
 		p4d[511] += load_delta;
 	}
@@ -111,7 +146,7 @@ void __head __startup_64(unsigned long physaddr)
 	pud = fixup_pointer(early_dynamic_pgts[next_early_pgt++], physaddr);
 	pmd = fixup_pointer(early_dynamic_pgts[next_early_pgt++], physaddr);
 
-	if (IS_ENABLED(CONFIG_X86_5LEVEL)) {
+	if (!p4d_folded) {
 		p4d = fixup_pointer(early_dynamic_pgts[next_early_pgt++], physaddr);
 
 		i = (physaddr >> PGDIR_SHIFT) % PTRS_PER_PGD;
@@ -153,8 +188,7 @@ void __head __startup_64(unsigned long physaddr)
 	}
 
 	/* Fixup phys_base */
-	p = fixup_pointer(&phys_base, physaddr);
-	*p += load_delta;
+	*fixup_long(&phys_base, physaddr) += load_delta;
 }
 
 /* Wipe all early page tables except for the kernel symbol map */
@@ -187,7 +221,7 @@ int __init early_make_pgtable(unsigned long address)
 	 * critical -- __PAGE_OFFSET would point us back into the dynamic
 	 * range and we might end up looping forever...
 	 */
-	if (!IS_ENABLED(CONFIG_X86_5LEVEL))
+	if (p4d_folded)
 		p4d_p = pgd_p;
 	else if (pgd)
 		p4d_p = (p4dval_t *)((pgd & PTE_PFN_MASK) + __START_KERNEL_map - phys_base);
diff --git a/arch/x86/kernel/head_64.S b/arch/x86/kernel/head_64.S
index 979b388d5e37..5e046a0225d9 100644
--- a/arch/x86/kernel/head_64.S
+++ b/arch/x86/kernel/head_64.S
@@ -40,7 +40,7 @@
 #define pud_index(x)	(((x) >> PUD_SHIFT) & (PTRS_PER_PUD-1))
 
 #if defined(CONFIG_XEN_PV) || defined(CONFIG_XEN_PVH)
-PGD_PAGE_OFFSET = pgd_index(__PAGE_OFFSET_BASE)
+PGD_PAGE_OFFSET = pgd_index(__PAGE_OFFSET_BASE48)
 PGD_START_KERNEL = pgd_index(__START_KERNEL_map)
 #endif
 L3_START_KERNEL = pud_index(__START_KERNEL_map)
@@ -105,7 +105,10 @@ ENTRY(secondary_startup_64)
 	/* Enable PAE mode, PGE and LA57 */
 	movl	$(X86_CR4_PAE | X86_CR4_PGE), %ecx
 #ifdef CONFIG_X86_5LEVEL
+	testl	$1, p4d_folded(%rip)
+	jnz	1f
 	orl	$X86_CR4_LA57, %ecx
+1:
 #endif
 	movq	%rcx, %cr4
 
@@ -334,12 +337,7 @@ GLOBAL(name)
 
 	__INITDATA
 NEXT_PAGE(early_top_pgt)
-	.fill	511,8,0
-#ifdef CONFIG_X86_5LEVEL
-	.quad	level4_kernel_pgt - __START_KERNEL_map + _PAGE_TABLE
-#else
-	.quad	level3_kernel_pgt - __START_KERNEL_map + _PAGE_TABLE
-#endif
+	.fill	512,8,0
 
 NEXT_PAGE(early_dynamic_pgts)
 	.fill	512*EARLY_DYNAMIC_PAGE_TABLES,8,0
@@ -418,6 +416,12 @@ ENTRY(phys_base)
 	.quad   0x0000000000000000
 EXPORT_SYMBOL(phys_base)
 
+#ifdef CONFIG_X86_5LEVEL
+ENTRY(p4d_folded)
+	.word	1
+EXPORT_SYMBOL(p4d_folded)
+#endif
+
 #include "../../x86/xen/xen-head.S"
 	
 	__PAGE_ALIGNED_BSS
diff --git a/arch/x86/mm/dump_pagetables.c b/arch/x86/mm/dump_pagetables.c
index 36531c2b7a88..de83151ad689 100644
--- a/arch/x86/mm/dump_pagetables.c
+++ b/arch/x86/mm/dump_pagetables.c
@@ -82,8 +82,8 @@ static struct addr_marker address_markers[] = {
 	{ 0/* VMALLOC_START */, "vmalloc() Area" },
 	{ 0/* VMEMMAP_START */, "Vmemmap" },
 #ifdef CONFIG_KASAN
-	{ KASAN_SHADOW_START,	"KASAN shadow" },
-	{ KASAN_SHADOW_END,	"KASAN shadow end" },
+	{ 0/* KASAN_SHADOW_START */,	"KASAN shadow" },
+	{ 0/* KASAN_SHADOW_END */,	"KASAN shadow end" },
 #endif
 # ifdef CONFIG_X86_ESPFIX64
 	{ ESPFIX_BASE_ADDR,	"ESPfix Area", 16 },
@@ -497,6 +497,10 @@ static int __init pt_dump_init(void)
 	address_markers[LOW_KERNEL_NR].start_address = PAGE_OFFSET;
 	address_markers[VMALLOC_START_NR].start_address = VMALLOC_START;
 	address_markers[VMEMMAP_START_NR].start_address = VMEMMAP_START;
+#ifdef CONFIG_KASAN
+	address_markers[KASAN_SHADOW_START_NR].start_address = KASAN_SHADOW_START;
+	address_markers[KASAN_SHADOW_END_NR].start_address = KASAN_SHADOW_END;
+#endif
 #endif
 #ifdef CONFIG_X86_32
 	address_markers[VMALLOC_START_NR].start_address = VMALLOC_START;
diff --git a/arch/x86/mm/kaslr.c b/arch/x86/mm/kaslr.c
index e6420b18f6e0..2f6ba5c72905 100644
--- a/arch/x86/mm/kaslr.c
+++ b/arch/x86/mm/kaslr.c
@@ -43,7 +43,6 @@
  * before. You also need to add a BUILD_BUG_ON() in kernel_randomize_memory() to
  * ensure that this order is correct and won't be changed.
  */
-static const unsigned long vaddr_start = __PAGE_OFFSET_BASE;
 
 #if defined(CONFIG_X86_ESPFIX64)
 static const unsigned long vaddr_end = ESPFIX_BASE_ADDR;
@@ -62,8 +61,8 @@ static __initdata struct kaslr_memory_region {
 	unsigned long *base;
 	unsigned long size_tb;
 } kaslr_regions[] = {
-	{ &page_offset_base, 1 << (__PHYSICAL_MASK_SHIFT - TB_SHIFT) /* Maximum */ },
-	{ &vmalloc_base, VMALLOC_SIZE_TB },
+	{ &page_offset_base, 0 },
+	{ &vmalloc_base, 0 },
 	{ &vmemmap_base, 1 },
 };
 
@@ -86,11 +85,14 @@ static inline bool kaslr_memory_enabled(void)
 void __init kernel_randomize_memory(void)
 {
 	size_t i;
-	unsigned long vaddr = vaddr_start;
+	unsigned long vaddr_start, vaddr;
 	unsigned long rand, memory_tb;
 	struct rnd_state rand_state;
 	unsigned long remain_entropy;
 
+	vaddr_start = p4d_folded ? __PAGE_OFFSET_BASE48 : __PAGE_OFFSET_BASE57;
+	vaddr = vaddr_start;
+
 	/*
 	 * All these BUILD_BUG_ON checks ensures the memory layout is
 	 * consistent with the vaddr_start/vaddr_end variables.
@@ -106,6 +108,9 @@ void __init kernel_randomize_memory(void)
 	if (!kaslr_memory_enabled())
 		return;
 
+	kaslr_regions[0].size_tb = 1 << (__PHYSICAL_MASK_SHIFT - TB_SHIFT);
+	kaslr_regions[1].size_tb = VMALLOC_SIZE_TB;
+
 	/*
 	 * Update Physical memory mapping to available and
 	 * add padding if needed (especially for memory hotplug support).
-- 
2.11.0

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