[PATCHv7 09/14] x86/boot/64: Add support of additional page table level during early boot

From: Kirill A. Shutemov
Date: Tue Jun 06 2017 - 07:31:52 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/include/asm/pgtable_64.h | 2 ++
arch/x86/include/uapi/asm/processor-flags.h | 2 ++
arch/x86/kernel/head64.c | 48 +++++++++++++++++++++++++----
arch/x86/kernel/head_64.S | 26 ++++++++++++----
4 files changed, 66 insertions(+), 12 deletions(-)

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 f8a2f34fa15d..9403633f4c7c 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;
@@ -87,9 +93,21 @@ 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);

- i = (physaddr >> PGDIR_SHIFT) % PTRS_PER_PGD;
- pgd[i + 0] = (pgdval_t)pud + _KERNPG_TABLE;
- pgd[i + 1] = (pgdval_t)pud + _KERNPG_TABLE;
+ if (IS_ENABLED(CONFIG_X86_5LEVEL)) {
+ p4d = fixup_pointer(early_dynamic_pgts[next_early_pgt++], physaddr);
+
+ i = (physaddr >> PGDIR_SHIFT) % PTRS_PER_PGD;
+ pgd[i + 0] = (pgdval_t)p4d + _KERNPG_TABLE;
+ pgd[i + 1] = (pgdval_t)p4d + _KERNPG_TABLE;
+
+ i = (physaddr >> P4D_SHIFT) % PTRS_PER_P4D;
+ p4d[i + 0] = (pgdval_t)pud + _KERNPG_TABLE;
+ p4d[i + 1] = (pgdval_t)pud + _KERNPG_TABLE;
+ } else {
+ i = (physaddr >> PGDIR_SHIFT) % PTRS_PER_PGD;
+ pgd[i + 0] = (pgdval_t)pud + _KERNPG_TABLE;
+ pgd[i + 1] = (pgdval_t)pud + _KERNPG_TABLE;
+ }

i = (physaddr >> PUD_SHIFT) % PTRS_PER_PUD;
pud[i + 0] = (pudval_t)pmd + _KERNPG_TABLE;
@@ -134,6 +152,7 @@ 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;

@@ -150,8 +169,25 @@ 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();
@@ -160,7 +196,7 @@ 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 0ae0bad4d4d5..6225550883df 100644
--- a/arch/x86/kernel/head_64.S
+++ b/arch/x86/kernel/head_64.S
@@ -37,10 +37,11 @@
*
*/

+#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)
L3_START_KERNEL = pud_index(__START_KERNEL_map)

.text
@@ -100,11 +101,14 @@ 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

@@ -330,7 +334,11 @@ 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
@@ -343,9 +351,9 @@ 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

@@ -359,6 +367,12 @@ 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: "[PATCHv7 03/14] x86/boot/efi: Cleanup initialization of GDT entries"
Previous message: Kirill A. Shutemov: "[PATCHv7 02/14] x86/asm: Fix comment in return_from_SYSCALL_64"
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