[PATCH 3/8] x86/boot/64: Add support of additional page table level during early boot

From: Kirill A. Shutemov
Date: Thu Apr 06 2017 - 10:01:32 EST

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This patch adds support for 5-level paging during early boot.
It generalizes boot for 4- and 5-level paging on 64-bit systems with
compile-time switch between them.

Signed-off-by: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx>
---
arch/x86/boot/compressed/head_64.S | 23 ++++++++++++---
arch/x86/include/asm/pgtable_64.h | 2 ++
arch/x86/include/uapi/asm/processor-flags.h | 2 ++
arch/x86/kernel/head64.c | 44 +++++++++++++++++++++++++----
arch/x86/kernel/head_64.S | 29 +++++++++++++++----
5 files changed, 85 insertions(+), 15 deletions(-)

diff --git a/arch/x86/boot/compressed/head_64.S b/arch/x86/boot/compressed/head_64.S
index d2ae1f821e0c..3ed26769810b 100644
--- a/arch/x86/boot/compressed/head_64.S
+++ b/arch/x86/boot/compressed/head_64.S
@@ -122,9 +122,12 @@ ENTRY(startup_32)
addl %ebp, gdt+2(%ebp)
lgdt gdt(%ebp)

- /* Enable PAE mode */
+ /* Enable PAE and LA57 mode */
movl %cr4, %eax
orl $X86_CR4_PAE, %eax
+#ifdef CONFIG_X86_5LEVEL
+ orl $X86_CR4_LA57, %eax
+#endif
movl %eax, %cr4

/*
@@ -136,13 +139,24 @@ ENTRY(startup_32)
movl $(BOOT_INIT_PGT_SIZE/4), %ecx
rep stosl

+ xorl %edx, %edx
+
+ /* Build Top Level */
+ leal pgtable(%ebx,%edx,1), %edi
+ leal 0x1007 (%edi), %eax
+ movl %eax, 0(%edi)
+
+#ifdef CONFIG_X86_5LEVEL
/* Build Level 4 */
- leal pgtable + 0(%ebx), %edi
+ addl $0x1000, %edx
+ leal pgtable(%ebx,%edx), %edi
leal 0x1007 (%edi), %eax
movl %eax, 0(%edi)
+#endif

/* Build Level 3 */
- leal pgtable + 0x1000(%ebx), %edi
+ addl $0x1000, %edx
+ leal pgtable(%ebx,%edx), %edi
leal 0x1007(%edi), %eax
movl $4, %ecx
1: movl %eax, 0x00(%edi)
@@ -152,7 +166,8 @@ ENTRY(startup_32)
jnz 1b

/* Build Level 2 */
- leal pgtable + 0x2000(%ebx), %edi
+ addl $0x1000, %edx
+ leal pgtable(%ebx,%edx), %edi
movl $0x00000183, %eax
movl $2048, %ecx
1: movl %eax, 0(%edi)
diff --git a/arch/x86/include/asm/pgtable_64.h b/arch/x86/include/asm/pgtable_64.h
index affcb2a9c563..2160c1fee920 100644
--- a/arch/x86/include/asm/pgtable_64.h
+++ b/arch/x86/include/asm/pgtable_64.h
@@ -14,6 +14,8 @@
#include <linux/bitops.h>
#include <linux/threads.h>

+extern p4d_t level4_kernel_pgt[512];
+extern p4d_t level4_ident_pgt[512];
extern pud_t level3_kernel_pgt[512];
extern pud_t level3_ident_pgt[512];
extern pmd_t level2_kernel_pgt[512];
diff --git a/arch/x86/include/uapi/asm/processor-flags.h b/arch/x86/include/uapi/asm/processor-flags.h
index 567de50a4c2a..185f3d10c194 100644
--- a/arch/x86/include/uapi/asm/processor-flags.h
+++ b/arch/x86/include/uapi/asm/processor-flags.h
@@ -104,6 +104,8 @@
#define X86_CR4_OSFXSR _BITUL(X86_CR4_OSFXSR_BIT)
#define X86_CR4_OSXMMEXCPT_BIT 10 /* enable unmasked SSE exceptions */
#define X86_CR4_OSXMMEXCPT _BITUL(X86_CR4_OSXMMEXCPT_BIT)
+#define X86_CR4_LA57_BIT 12 /* enable 5-level page tables */
+#define X86_CR4_LA57 _BITUL(X86_CR4_LA57_BIT)
#define X86_CR4_VMXE_BIT 13 /* enable VMX virtualization */
#define X86_CR4_VMXE _BITUL(X86_CR4_VMXE_BIT)
#define X86_CR4_SMXE_BIT 14 /* enable safer mode (TXT) */
diff --git a/arch/x86/kernel/head64.c b/arch/x86/kernel/head64.c
index c46e0f62024e..92935855eaaa 100644
--- a/arch/x86/kernel/head64.c
+++ b/arch/x86/kernel/head64.c
@@ -47,6 +47,7 @@ void __init __startup_64(unsigned long physaddr)
{
unsigned long load_delta, *p;
pgdval_t *pgd;
+ p4dval_t *p4d;
pudval_t *pud;
pmdval_t *pmd, pmd_entry;
int i;
@@ -70,6 +71,11 @@ void __init __startup_64(unsigned long physaddr)
pgd = fixup_pointer(&early_top_pgt, physaddr);
pgd[pgd_index(__START_KERNEL_map)] += load_delta;

+ if (IS_ENABLED(CONFIG_X86_5LEVEL)) {
+ p4d = fixup_pointer(&level4_kernel_pgt, physaddr);
+ p4d[511] += load_delta;
+ }
+
pud = fixup_pointer(&level3_kernel_pgt, physaddr);
pud[510] += load_delta;
pud[511] += load_delta;
@@ -87,8 +93,18 @@ void __init __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);

- pgd[0] = (pgdval_t)pud + _KERNPG_TABLE;
- pgd[1] = (pgdval_t)pud + _KERNPG_TABLE;
+ if (IS_ENABLED(CONFIG_X86_5LEVEL)) {
+ p4d = fixup_pointer(early_dynamic_pgts[next_early_pgt++], physaddr);
+
+ pgd[0] = (pgdval_t)p4d + _KERNPG_TABLE;
+ pgd[1] = (pgdval_t)p4d + _KERNPG_TABLE;
+
+ p4d[0] = (pgdval_t)pud + _KERNPG_TABLE;
+ p4d[1] = (pgdval_t)pud + _KERNPG_TABLE;
+ } else {
+ pgd[0] = (pgdval_t)pud + _KERNPG_TABLE;
+ pgd[1] = (pgdval_t)pud + _KERNPG_TABLE;
+ }

pud[0] = (pudval_t)pmd + _KERNPG_TABLE;
pud[1] = (pudval_t)pmd + _KERNPG_TABLE;
@@ -130,6 +146,7 @@ int __init early_make_pgtable(unsigned long address)
{
unsigned long physaddr = address - __PAGE_OFFSET;
pgdval_t pgd, *pgd_p;
+ p4dval_t p4d, *p4d_p;
pudval_t pud, *pud_p;
pmdval_t pmd, *pmd_p;

@@ -146,8 +163,25 @@ 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 (pgd)
- pud_p = (pudval_t *)((pgd & PTE_PFN_MASK) + __START_KERNEL_map - phys_base);
+ if (!IS_ENABLED(CONFIG_X86_5LEVEL))
+ p4d_p = pgd_p;
+ else if (pgd)
+ p4d_p = (p4dval_t *)((pgd & PTE_PFN_MASK) + __START_KERNEL_map - phys_base);
+ else {
+ if (next_early_pgt >= EARLY_DYNAMIC_PAGE_TABLES) {
+ reset_early_page_tables();
+ goto again;
+ }
+
+ p4d_p = (p4dval_t *)early_dynamic_pgts[next_early_pgt++];
+ memset(p4d_p, 0, sizeof(*p4d_p) * PTRS_PER_P4D);
+ *pgd_p = (pgdval_t)p4d_p - __START_KERNEL_map + phys_base + _KERNPG_TABLE;
+ }
+ p4d_p += p4d_index(address);
+ p4d = *p4d_p;
+
+ if (p4d)
+ pud_p = (pudval_t *)((p4d & PTE_PFN_MASK) + __START_KERNEL_map - phys_base);
else {
if (next_early_pgt >= EARLY_DYNAMIC_PAGE_TABLES) {
reset_early_page_tables();
@@ -156,7 +190,7 @@ int __init early_make_pgtable(unsigned long address)

pud_p = (pudval_t *)early_dynamic_pgts[next_early_pgt++];
memset(pud_p, 0, sizeof(*pud_p) * PTRS_PER_PUD);
- *pgd_p = (pgdval_t)pud_p - __START_KERNEL_map + phys_base + _KERNPG_TABLE;
+ *p4d_p = (p4dval_t)pud_p - __START_KERNEL_map + phys_base + _KERNPG_TABLE;
}
pud_p += pud_index(address);
pud = *pud_p;
diff --git a/arch/x86/kernel/head_64.S b/arch/x86/kernel/head_64.S
index d44c350797bf..b24fc575a6da 100644
--- a/arch/x86/kernel/head_64.S
+++ b/arch/x86/kernel/head_64.S
@@ -37,10 +37,14 @@
*
*/

+#define p4d_index(x) (((x) >> P4D_SHIFT) & (PTRS_PER_P4D-1))
#define pud_index(x) (((x) >> PUD_SHIFT) & (PTRS_PER_PUD-1))

-L4_PAGE_OFFSET = pgd_index(__PAGE_OFFSET_BASE)
-L4_START_KERNEL = pgd_index(__START_KERNEL_map)
+PGD_PAGE_OFFSET = pgd_index(__PAGE_OFFSET_BASE)
+PGD_START_KERNEL = pgd_index(__START_KERNEL_map)
+#ifdef CONFIG_X86_5LEVEL
+L4_START_KERNEL = p4d_index(__START_KERNEL_map)
+#endif
L3_START_KERNEL = pud_index(__START_KERNEL_map)

.text
@@ -98,11 +102,14 @@ ENTRY(secondary_startup_64)
movq $(init_top_pgt - __START_KERNEL_map), %rax
1:

- /* Enable PAE mode and PGE */
+ /* Enable PAE mode, PGE and LA57 */
movl $(X86_CR4_PAE | X86_CR4_PGE), %ecx
+#ifdef CONFIG_X86_5LEVEL
+ orl $X86_CR4_LA57, %ecx
+#endif
movq %rcx, %cr4

- /* Setup early boot stage 4 level pagetables. */
+ /* Setup early boot stage 4-/5-level pagetables. */
addq phys_base(%rip), %rax
movq %rax, %cr3

@@ -328,7 +335,11 @@ 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

NEXT_PAGE(early_dynamic_pgts)
.fill 512*EARLY_DYNAMIC_PAGE_TABLES,8,0
@@ -341,9 +352,9 @@ NEXT_PAGE(init_top_pgt)
#else
NEXT_PAGE(init_top_pgt)
.quad level3_ident_pgt - __START_KERNEL_map + _KERNPG_TABLE
- .org init_top_pgt + L4_PAGE_OFFSET*8, 0
+ .org init_top_pgt + PGD_PAGE_OFFSET*8, 0
.quad level3_ident_pgt - __START_KERNEL_map + _KERNPG_TABLE
- .org init_top_pgt + L4_START_KERNEL*8, 0
+ .org init_top_pgt + PGD_START_KERNEL*8, 0
/* (2^48-(2*1024*1024*1024))/(2^39) = 511 */
.quad level3_kernel_pgt - __START_KERNEL_map + _PAGE_TABLE

@@ -357,6 +368,12 @@ NEXT_PAGE(level2_ident_pgt)
PMDS(0, __PAGE_KERNEL_IDENT_LARGE_EXEC, PTRS_PER_PMD)
#endif

+#ifdef CONFIG_X86_5LEVEL
+NEXT_PAGE(level4_kernel_pgt)
+ .fill 511,8,0
+ .quad level3_kernel_pgt - __START_KERNEL_map + _PAGE_TABLE
+#endif
+
NEXT_PAGE(level3_kernel_pgt)
.fill L3_START_KERNEL,8,0
/* (2^48-(2*1024*1024*1024)-((2^39)*511))/(2^30) = 510 */
--
2.11.0

Next message: Kirill A. Shutemov: "[PATCH 4/8] x86/mm: Add sync_global_pgds() for configuration with 5-level paging"
Previous message: Kirill A. Shutemov: "[PATCH 2/8] x86/boot/64: Rename init_level4_pgt and early_level4_pgt"
In reply to: Kirill A. Shutemov: "[PATCH 2/8] x86/boot/64: Rename init_level4_pgt and early_level4_pgt"
Next in thread: Kirill A. Shutemov: "[PATCH 4/8] x86/mm: Add sync_global_pgds() for configuration with 5-level paging"
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