Merge branch 'x86-mm-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull x86 mm updates from Ingo Molnar:
 "The main changes in this cycle were:

   - Continued work to add support for 5-level paging provided by future
     Intel CPUs. In particular we switch the x86 GUP code to the generic
     implementation. (Kirill A. Shutemov)

   - Continued work to add PCID CPU support to native kernels as well.
     In this round most of the focus is on reworking/refreshing the TLB
     flush infrastructure for the upcoming PCID changes. (Andy
     Lutomirski)"

* 'x86-mm-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (34 commits)
  x86/mm: Delete a big outdated comment about TLB flushing
  x86/mm: Don't reenter flush_tlb_func_common()
  x86/KASLR: Fix detection 32/64 bit bootloaders for 5-level paging
  x86/ftrace: Exclude functions in head64.c from function-tracing
  x86/mmap, ASLR: Do not treat unlimited-stack tasks as legacy mmap
  x86/mm: Remove reset_lazy_tlbstate()
  x86/ldt: Simplify the LDT switching logic
  x86/boot/64: Put __startup_64() into .head.text
  x86/mm: Add support for 5-level paging for KASLR
  x86/mm: Make kernel_physical_mapping_init() support 5-level paging
  x86/mm: Add sync_global_pgds() for configuration with 5-level paging
  x86/boot/64: Add support of additional page table level during early boot
  x86/boot/64: Rename init_level4_pgt and early_level4_pgt
  x86/boot/64: Rewrite startup_64() in C
  x86/boot/compressed: Enable 5-level paging during decompression stage
  x86/boot/efi: Define __KERNEL32_CS GDT on 64-bit configurations
  x86/boot/efi: Fix __KERNEL_CS definition of GDT entry on 64-bit configurations
  x86/boot/efi: Cleanup initialization of GDT entries
  x86/asm: Fix comment in return_from_SYSCALL_64()
  x86/mm/gup: Switch GUP to the generic get_user_page_fast() implementation
  ...

arch/x86/boot/compressed/eboot.c

@@ -1046,9 +1046,31 @@ struct boot_params *efi_main(struct efi_config *c,
 	memset((char *)gdt->address, 0x0, gdt->size);
 	desc = (struct desc_struct *)gdt->address;
 
-	/* The first GDT is a dummy and the second is unused. */
-	desc += 2;
+	/* The first GDT is a dummy. */
+	desc++;
 
+	if (IS_ENABLED(CONFIG_X86_64)) {
+		/* __KERNEL32_CS */
+		desc->limit0 = 0xffff;
+		desc->base0 = 0x0000;
+		desc->base1 = 0x0000;
+		desc->type = SEG_TYPE_CODE | SEG_TYPE_EXEC_READ;
+		desc->s = DESC_TYPE_CODE_DATA;
+		desc->dpl = 0;
+		desc->p = 1;
+		desc->limit = 0xf;
+		desc->avl = 0;
+		desc->l = 0;
+		desc->d = SEG_OP_SIZE_32BIT;
+		desc->g = SEG_GRANULARITY_4KB;
+		desc->base2 = 0x00;
+		desc++;
+	} else {
+		/* Second entry is unused on 32-bit */
+		desc++;
+	}
+
+	/* __KERNEL_CS */
 	desc->limit0 = 0xffff;
 	desc->base0 = 0x0000;
 	desc->base1 = 0x0000;
@@ -1058,12 +1080,18 @@ struct boot_params *efi_main(struct efi_config *c,
 	desc->p = 1;
 	desc->limit = 0xf;
 	desc->avl = 0;
-	desc->l = 0;
-	desc->d = SEG_OP_SIZE_32BIT;
+	if (IS_ENABLED(CONFIG_X86_64)) {
+		desc->l = 1;
+		desc->d = 0;
+	} else {
+		desc->l = 0;
+		desc->d = SEG_OP_SIZE_32BIT;
+	}
 	desc->g = SEG_GRANULARITY_4KB;
 	desc->base2 = 0x00;
-
 	desc++;
+
+	/* __KERNEL_DS */
 	desc->limit0 = 0xffff;
 	desc->base0 = 0x0000;
 	desc->base1 = 0x0000;
@@ -1077,24 +1105,25 @@ struct boot_params *efi_main(struct efi_config *c,
 	desc->d = SEG_OP_SIZE_32BIT;
 	desc->g = SEG_GRANULARITY_4KB;
 	desc->base2 = 0x00;
-
-#ifdef CONFIG_X86_64
-	/* Task segment value */
 	desc++;
-	desc->limit0 = 0x0000;
-	desc->base0 = 0x0000;
-	desc->base1 = 0x0000;
-	desc->type = SEG_TYPE_TSS;
-	desc->s = 0;
-	desc->dpl = 0;
-	desc->p = 1;
-	desc->limit = 0x0;
-	desc->avl = 0;
-	desc->l = 0;
-	desc->d = 0;
-	desc->g = SEG_GRANULARITY_4KB;
-	desc->base2 = 0x00;
-#endif /* CONFIG_X86_64 */
+
+	if (IS_ENABLED(CONFIG_X86_64)) {
+		/* Task segment value */
+		desc->limit0 = 0x0000;
+		desc->base0 = 0x0000;
+		desc->base1 = 0x0000;
+		desc->type = SEG_TYPE_TSS;
+		desc->s = 0;
+		desc->dpl = 0;
+		desc->p = 1;
+		desc->limit = 0x0;
+		desc->avl = 0;
+		desc->l = 0;
+		desc->d = 0;
+		desc->g = SEG_GRANULARITY_4KB;
+		desc->base2 = 0x00;
+		desc++;
+	}
 
 	asm volatile("cli");
 	asm volatile ("lgdt %0" : : "m" (*gdt));

arch/x86/boot/compressed/head_64.S

@@ -346,6 +346,48 @@ preferred_addr:
 	/* Set up the stack */
 	leaq	boot_stack_end(%rbx), %rsp
 
+#ifdef CONFIG_X86_5LEVEL
+	/* Check if 5-level paging has already enabled */
+	movq	%cr4, %rax
+	testl	$X86_CR4_LA57, %eax
+	jnz	lvl5
+
+	/*
+	 * At this point we are in long mode with 4-level paging enabled,
+	 * but we want to enable 5-level paging.
+	 *
+	 * The problem is that we cannot do it directly. Setting LA57 in
+	 * long mode would trigger #GP. So we need to switch off long mode
+	 * first.
+	 *
+	 * NOTE: This is not going to work if bootloader put us above 4G
+	 * limit.
+	 *
+	 * The first step is go into compatibility mode.
+	 */
+
+	/* Clear additional page table */
+	leaq	lvl5_pgtable(%rbx), %rdi
+	xorq	%rax, %rax
+	movq	$(PAGE_SIZE/8), %rcx
+	rep	stosq
+
+	/*
+	 * Setup current CR3 as the first and only entry in a new top level
+	 * page table.
+	 */
+	movq	%cr3, %rdi
+	leaq	0x7 (%rdi), %rax
+	movq	%rax, lvl5_pgtable(%rbx)
+
+	/* Switch to compatibility mode (CS.L = 0 CS.D = 1) via far return */
+	pushq	$__KERNEL32_CS
+	leaq	compatible_mode(%rip), %rax
+	pushq	%rax
+	lretq
+lvl5:
+#endif
+
 	/* Zero EFLAGS */
 	pushq	$0
 	popfq
@@ -429,6 +471,44 @@ relocated:
 	jmp	*%rax
 
 	.code32
+#ifdef CONFIG_X86_5LEVEL
+compatible_mode:
+	/* Setup data and stack segments */
+	movl	$__KERNEL_DS, %eax
+	movl	%eax, %ds
+	movl	%eax, %ss
+
+	/* Disable paging */
+	movl	%cr0, %eax
+	btrl	$X86_CR0_PG_BIT, %eax
+	movl	%eax, %cr0
+
+	/* Point CR3 to 5-level paging */
+	leal	lvl5_pgtable(%ebx), %eax
+	movl	%eax, %cr3
+
+	/* Enable PAE and LA57 mode */
+	movl	%cr4, %eax
+	orl	$(X86_CR4_PAE | X86_CR4_LA57), %eax
+	movl	%eax, %cr4
+
+	/* Calculate address we are running at */
+	call	1f
+1:	popl	%edi
+	subl	$1b, %edi
+
+	/* Prepare stack for far return to Long Mode */
+	pushl	$__KERNEL_CS
+	leal	lvl5(%edi), %eax
+	push	%eax
+
+	/* Enable paging back */
+	movl	$(X86_CR0_PG | X86_CR0_PE), %eax
+	movl	%eax, %cr0
+
+	lret
+#endif
+
 no_longmode:
 	/* This isn't an x86-64 CPU so hang */
 1:
@@ -442,7 +522,7 @@ gdt:
 	.word	gdt_end - gdt
 	.long	gdt
 	.word	0
-	.quad	0x0000000000000000	/* NULL descriptor */
+	.quad	0x00cf9a000000ffff	/* __KERNEL32_CS */
 	.quad	0x00af9a000000ffff	/* __KERNEL_CS */
 	.quad	0x00cf92000000ffff	/* __KERNEL_DS */
 	.quad	0x0080890000000000	/* TS descriptor */
@@ -486,3 +566,7 @@ boot_stack_end:
 	.balign 4096
 pgtable:
 	.fill BOOT_PGT_SIZE, 1, 0
+#ifdef CONFIG_X86_5LEVEL
+lvl5_pgtable:
+	.fill PAGE_SIZE, 1, 0
+#endif

arch/x86/boot/compressed/pagetable.c

@@ -63,7 +63,7 @@ static void *alloc_pgt_page(void *context)
 static struct alloc_pgt_data pgt_data;
 
 /* The top level page table entry pointer. */
-static unsigned long level4p;
+static unsigned long top_level_pgt;
 
 /*
  * Mapping information structure passed to kernel_ident_mapping_init().
@@ -91,9 +91,15 @@ void initialize_identity_maps(void)
 	 * If we came here via startup_32(), cr3 will be _pgtable already
 	 * and we must append to the existing area instead of entirely
 	 * overwriting it.
+	 *
+	 * With 5-level paging, we use '_pgtable' to allocate the p4d page table,
+	 * the top-level page table is allocated separately.
+	 *
+	 * p4d_offset(top_level_pgt, 0) would cover both the 4- and 5-level
+	 * cases. On 4-level paging it's equal to 'top_level_pgt'.
 	 */
-	level4p = read_cr3();
-	if (level4p == (unsigned long)_pgtable) {
+	top_level_pgt = read_cr3_pa();
+	if (p4d_offset((pgd_t *)top_level_pgt, 0) == (p4d_t *)_pgtable) {
 		debug_putstr("booted via startup_32()\n");
 		pgt_data.pgt_buf = _pgtable + BOOT_INIT_PGT_SIZE;
 		pgt_data.pgt_buf_size = BOOT_PGT_SIZE - BOOT_INIT_PGT_SIZE;
@@ -103,7 +109,7 @@ void initialize_identity_maps(void)
 		pgt_data.pgt_buf = _pgtable;
 		pgt_data.pgt_buf_size = BOOT_PGT_SIZE;
 		memset(pgt_data.pgt_buf, 0, pgt_data.pgt_buf_size);
-		level4p = (unsigned long)alloc_pgt_page(&pgt_data);
+		top_level_pgt = (unsigned long)alloc_pgt_page(&pgt_data);
 	}
 }
 
@@ -123,7 +129,7 @@ void add_identity_map(unsigned long start, unsigned long size)
 		return;
 
 	/* Build the mapping. */
-	kernel_ident_mapping_init(&mapping_info, (pgd_t *)level4p,
+	kernel_ident_mapping_init(&mapping_info, (pgd_t *)top_level_pgt,
 				  start, end);
 }
 
@@ -134,5 +140,5 @@ void add_identity_map(unsigned long start, unsigned long size)
  */
 void finalize_identity_maps(void)
 {
-	write_cr3(level4p);
+	write_cr3(top_level_pgt);
 }