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* [PATCH RFC] riscv: Introduce compile-time early page table for XIP kernel
@ 2021-08-05  9:55 Alexandre Ghiti
  2021-08-25  5:09 ` Palmer Dabbelt
  0 siblings, 1 reply; 2+ messages in thread
From: Alexandre Ghiti @ 2021-08-05  9:55 UTC (permalink / raw)
  To: Paul Walmsley, Palmer Dabbelt, Albert Ou, Vitaly Wool,
	Jisheng Zhang, Atish Patra, linux-riscv, linux-kernel
  Cc: Alexandre Ghiti

As described in [1], XIP kernel current implementation introduces a few
drawbacks caused by the 'fixups'.

All those fixups are necessary because the MMU is not enabled soon enough:
this patch introduces a way to compute the early page table at
'compile-time' by generating, from the XIP config, a linker script that
contains the early page table definition.

A python script is used to generate the early page table: for now, it
redefines quite a few macros from the C code, but I have at least one
way to retrieve those values to avoid duplicating their definitions.

XIP kernel then loads the static early page table before accessing any
global variable in C and then avoids all the fixups.

This is an RFC as there are quite a few things to clean and improve.

[1] https://patchwork.kernel.org/project/linux-riscv/patch/20210618142353.2114854-1-alex@ghiti.fr/

Signed-off-by: Alexandre Ghiti <alex@ghiti.fr>
---
 arch/riscv/Makefile                           |  11 ++
 arch/riscv/include/asm/pgtable.h              |  22 +--
 .../riscv/kernel/generate-early-page-table.py | 154 ++++++++++++++++++
 arch/riscv/kernel/head.S                      |  62 +++++--
 arch/riscv/kernel/setup.c                     |   2 +-
 arch/riscv/kernel/vmlinux-xip.lds.S           |   3 +
 arch/riscv/mm/init.c                          | 140 ++++++++--------
 7 files changed, 286 insertions(+), 108 deletions(-)
 create mode 100755 arch/riscv/kernel/generate-early-page-table.py

diff --git a/arch/riscv/Makefile b/arch/riscv/Makefile
index bc74afdbf31e..6adb28bacc1a 100644
--- a/arch/riscv/Makefile
+++ b/arch/riscv/Makefile
@@ -123,6 +123,17 @@ $(BOOT_TARGETS): vmlinux
 	$(Q)$(MAKE) $(build)=$(boot) $(boot)/$@
 	@$(kecho) '  Kernel: $(boot)/$@ is ready'
 
+ifeq ($(CONFIG_XIP_KERNEL),y)
+vmlinux: early-page-table.lds.S
+
+quiet_cmd_generate_early_page_table = GENPGT  $@
+cmd_generate_early_page_table =	$(srctree)/arch/riscv/kernel/generate-early-page-table.py .config
+
+# TODO this is always called even without modifications!
+early-page-table.lds.S: $(srctree)/arch/riscv/kernel/generate-early-page-table.py
+	$(call if_changed,generate_early_page_table)
+endif
+
 Image.%: Image
 	$(Q)$(MAKE) $(build)=$(boot) $(boot)/$@
 
diff --git a/arch/riscv/include/asm/pgtable.h b/arch/riscv/include/asm/pgtable.h
index 39b550310ec6..8fef6f7bc22d 100644
--- a/arch/riscv/include/asm/pgtable.h
+++ b/arch/riscv/include/asm/pgtable.h
@@ -94,17 +94,6 @@
 #include <asm/pgtable-32.h>
 #endif /* CONFIG_64BIT */
 
-#ifdef CONFIG_XIP_KERNEL
-#define XIP_FIXUP(addr) ({							\
-	uintptr_t __a = (uintptr_t)(addr);					\
-	(__a >= CONFIG_XIP_PHYS_ADDR && __a < CONFIG_XIP_PHYS_ADDR + SZ_16M) ?	\
-		__a - CONFIG_XIP_PHYS_ADDR + CONFIG_PHYS_RAM_BASE - XIP_OFFSET :\
-		__a;								\
-	})
-#else
-#define XIP_FIXUP(addr)		(addr)
-#endif /* CONFIG_XIP_KERNEL */
-
 #ifdef CONFIG_MMU
 /* Number of entries in the page global directory */
 #define PTRS_PER_PGD    (PAGE_SIZE / sizeof(pgd_t))
@@ -680,15 +669,8 @@ static inline pmd_t pmdp_establish(struct vm_area_struct *vma,
 #define kern_addr_valid(addr)   (1) /* FIXME */
 
 extern char _start[];
-extern void *_dtb_early_va;
-extern uintptr_t _dtb_early_pa;
-#if defined(CONFIG_XIP_KERNEL) && defined(CONFIG_MMU)
-#define dtb_early_va	(*(void **)XIP_FIXUP(&_dtb_early_va))
-#define dtb_early_pa	(*(uintptr_t *)XIP_FIXUP(&_dtb_early_pa))
-#else
-#define dtb_early_va	_dtb_early_va
-#define dtb_early_pa	_dtb_early_pa
-#endif /* CONFIG_XIP_KERNEL */
+extern void *dtb_early_va;
+extern uintptr_t dtb_early_pa;
 
 void paging_init(void);
 void misc_mem_init(void);
diff --git a/arch/riscv/kernel/generate-early-page-table.py b/arch/riscv/kernel/generate-early-page-table.py
new file mode 100755
index 000000000000..98a401355932
--- /dev/null
+++ b/arch/riscv/kernel/generate-early-page-table.py
@@ -0,0 +1,154 @@
+#!/usr/bin/env python
+
+from os import path
+import sys
+import re
+
+if len(sys.argv) != 2:
+	print("Usage: %s PATH_TO_CONFIG" % sys.argv[0])
+	sys.exit(1)
+
+EARLY_PAGE_TABLE_LDS_PATH = path.join(path.dirname(path.abspath(__file__)), "early-page-table.lds.S")
+
+# PAGE_SIZE / sizeof(uint64_t)
+PTRS_PER_PGD = 512
+PTRS_PER_PMD = 512
+PTRS_PER_PTE = 512
+
+KERNEL_PGDS_NR = int(PTRS_PER_PGD / 2)
+
+PAGE_PFN_SHIFT = 10
+PAGE_SHIFT = 12
+PAGE_SIZE = 1 << PAGE_SHIFT
+PMD_SIZE = 1 << 21
+PGDIR_SIZE = 1 << 30
+
+TASK_SIZE = int(PGDIR_SIZE * PTRS_PER_PGD / 2)
+KERNEL_MAPPING_BASE_ADDR = 0xFFFFFFFFFFFFFFFF - TASK_SIZE + 1
+KERNEL_LINK_ADDR = 0xFFFFFFFF80000000
+FIXADDR_START = 0xFFFFFFCEFEE00000
+DTB_EARLY_BASE_VA = PGDIR_SIZE
+
+PAGE_KERNEL_EXEC = (1 << 1) | (1 << 2) | (1 << 0) | (1 << 6) | (1 << 7) | (1 << 5) | (1 << 3)
+PAGE_TABLE = (1 << 0)
+
+XIP_OFFSET = 8 * 1024 * 1024
+
+def extract_addr_from_config(config_path):
+	with open(config_path, "r") as fconfig:
+		content = fconfig.read()
+		p = re.compile('CONFIG_PHYS_RAM_BASE=.*').search(content)
+		if p:
+			phys_ram_base = p.group().split('=')[1]
+		else:
+			print("Can't find CONFIG_PHYS_RAM_BASE in .config!")
+			sys.exit(1)
+
+		p = re.compile("CONFIG_XIP_PHYS_ADDR=.*").search(content)
+		if p:
+			xip_phys_addr = p.group().split('=')[1]
+		else:
+			print("Can't find CONFIG_XIP_PHYS_ADDR in .config!")
+			sys.exit(1)
+
+		p = re.compile("CONFIG_BUILTIN_DTB.*").search(content)
+		if p:
+			builtin_dtb = True if p.group() == "CONFIG_BUILTIN_DTB=y" else False
+		else:
+			builtin_dtb = False
+
+	return (phys_ram_base, xip_phys_addr, builtin_dtb)
+
+def pte_page_table(phys_addr):
+	return "((({}) >> {}) << {}) | 0x{:x}".format(phys_addr, PAGE_SHIFT, PAGE_PFN_SHIFT, PAGE_TABLE)
+
+def pte_page_kernel_exec(phys_addr):
+	return "((({}) >> {}) << {}) | 0x{:x}".format(phys_addr, PAGE_SHIFT, PAGE_PFN_SHIFT, PAGE_KERNEL_EXEC)
+
+def pgd_entry_index(addr):
+	if addr >= KERNEL_MAPPING_BASE_ADDR:
+		return int((addr  - KERNEL_MAPPING_BASE_ADDR) / PGDIR_SIZE) + KERNEL_PGDS_NR
+	else:
+		return int(addr / PGDIR_SIZE)
+
+def pmd_entry_index(addr):
+	offset_in_pgdir = addr & (PGDIR_SIZE - 1)
+	return int(offset_in_pgdir / PMD_SIZE)
+
+def pte_entry_index(addr):
+	offset_in_pgdir = addr & (PMD_SIZE - 1)
+	return int(offset_in_pgdir / PAGE_SIZE)
+
+def create_kernel_page_table():
+	pgdir_kernel_mapping_entry = pgd_entry_index(KERNEL_LINK_ADDR)
+	early_pg_dir[pgdir_kernel_mapping_entry] = pte_page_table("XIP_PHYS_ADDR(early_pmd)")
+
+	# First half resides in flash
+	for i in range(0, int(XIP_OFFSET / PMD_SIZE)):
+		early_pmd[i] = pte_page_kernel_exec(str(hex(int(xip_phys_addr, 0) + i * PMD_SIZE)))
+
+	# Second half is in RAM
+	for i in range(int(XIP_OFFSET / PMD_SIZE), int(2 * XIP_OFFSET / PMD_SIZE)):
+		early_pmd[i] = pte_page_kernel_exec(str(hex(int(phys_ram_base, 0) + i * PMD_SIZE - XIP_OFFSET)))
+
+def create_fixaddr_page_table():
+	pgdir_fixaddr_entry = pgd_entry_index(FIXADDR_START)
+	early_pg_dir[pgdir_fixaddr_entry] = pte_page_table("RAM_PHYS_ADDR(fixmap_pmd)")
+
+	pmd_fixaddr_entry = pmd_entry_index(FIXADDR_START)
+	fixmap_pmd[pmd_fixaddr_entry] = pte_page_table("RAM_PHYS_ADDR(fixmap_pte)")
+
+def create_fdt_early_page_table():
+	pgdir_fdt_entry = pgd_entry_index(DTB_EARLY_BASE_VA)
+	early_pg_dir[pgdir_fdt_entry] = pte_page_table("RAM_PHYS_ADDR(early_dtb_pmd)")
+
+	pmd_fdt_entry = pmd_entry_index(DTB_EARLY_BASE_VA)
+	early_dtb_pmd[pmd_fdt_entry] = pte_page_kernel_exec("XIP_PHYS_ADDR(__dtb_start)")
+	early_dtb_pmd[pmd_fdt_entry + 1] = pte_page_kernel_exec("XIP_PHYS_ADDR(__dtb_start) + {}".format(PMD_SIZE))
+
+def setup_vm():
+	create_kernel_page_table()
+	create_fixaddr_page_table()
+	if not builtin_dtb:
+		create_fdt_early_page_table()
+
+def dump_macros(f):
+	f.write("#define XIP_PHYS_ADDR(x) ((x) - KERNEL_LINK_ADDR + {})\n".format(xip_phys_addr))
+	f.write("#define RAM_PHYS_ADDR(x) ((x) - KERNEL_LINK_ADDR + {} - 0x{:x})\n".format(phys_ram_base, XIP_OFFSET))
+	f.write("\n")
+
+def dump_section_header(f):
+	f.write(".init.early_page_table :\n")
+	f.write("{\n")
+
+def dump_section_footer(f):
+	f.write("}\n")
+
+def dump_page_table_level(f, ptl, nr_entries, ptl_name):
+	f.write("\t{} = .;\n".format(ptl_name))
+	for i in range(0, nr_entries):
+		f.write("\tQUAD({})\n".format(ptl[i]))
+
+def dump_page_table(f):
+	dump_page_table_level(f, early_pg_dir, PTRS_PER_PGD, "early_pg_dir")
+	dump_page_table_level(f, early_pmd, PTRS_PER_PMD, "early_pmd")
+	dump_page_table_level(f, fixmap_pmd, PTRS_PER_PMD, "fixmap_pmd")
+	dump_page_table_level(f, fixmap_pte, PTRS_PER_PTE, "fixmap_pte")
+	if not builtin_dtb:
+		dump_page_table_level(f, early_dtb_pmd, PTRS_PER_PMD, "early_dtb_pmd")
+
+early_pg_dir = [ "0" ] * PTRS_PER_PGD
+early_pmd = [ "0" ] * PTRS_PER_PMD
+fixmap_pmd = [ "0" ] * PTRS_PER_PMD
+fixmap_pte = [ "0" ] * PTRS_PER_PTE
+early_dtb_pmd = [ "0" ] * PTRS_PER_PMD
+
+(phys_ram_base, xip_phys_addr, builtin_dtb) = extract_addr_from_config(sys.argv[1])
+
+setup_vm()
+
+with open(EARLY_PAGE_TABLE_LDS_PATH, "w") as flds:
+	dump_macros(flds)
+	dump_section_header(flds)
+	dump_page_table(flds)
+	dump_section_footer(flds)
diff --git a/arch/riscv/kernel/head.S b/arch/riscv/kernel/head.S
index fce5184b22c3..bbc42c335cdb 100644
--- a/arch/riscv/kernel/head.S
+++ b/arch/riscv/kernel/head.S
@@ -79,11 +79,12 @@ pe_head_start:
 
 .align 2
 #ifdef CONFIG_MMU
+
+# a0: page directory address
+# a1: kernel virtual address
+# returns: relocated return address
 relocate:
 	/* Relocate return address */
-	la a1, kernel_map
-	XIP_FIXUP_OFFSET a1
-	REG_L a1, KERNEL_MAP_VIRT_ADDR(a1)
 	la a2, _start
 	sub a1, a1, a2
 	add ra, ra, a1
@@ -98,6 +99,7 @@ relocate:
 	li a1, SATP_MODE
 	or a2, a2, a1
 
+#ifndef CONFIG_XIP_KERNEL
 	/*
 	 * Load trampoline page directory, which will cause us to trap to
 	 * stvec if VA != PA, or simply fall through if VA == PA.  We need a
@@ -105,11 +107,21 @@ relocate:
 	 * to ensure the new translations are in use.
 	 */
 	la a0, trampoline_pg_dir
-	XIP_FIXUP_OFFSET a0
 	srl a0, a0, PAGE_SHIFT
 	or a0, a0, a1
 	sfence.vma
 	csrw CSR_SATP, a0
+#else
+	/*
+	 * Switch to kernel page tables.  A full fence is necessary in order to
+	 * avoid using the trampoline translations, which are only correct for
+	 * the first superpage.  Fetching the fence is guarnteed to work
+	 * because that first superpage is translated the same way.
+	 */
+	csrw CSR_SATP, a2
+	sfence.vma
+#endif
+
 .align 2
 1:
 	/* Set trap vector to spin forever to help debug */
@@ -121,7 +133,7 @@ relocate:
 .option norelax
 	la gp, __global_pointer$
 .option pop
-
+#ifndef CONFIG_XIP_KERNEL
 	/*
 	 * Switch to kernel page tables.  A full fence is necessary in order to
 	 * avoid using the trampoline translations, which are only correct for
@@ -130,6 +142,7 @@ relocate:
 	 */
 	csrw CSR_SATP, a2
 	sfence.vma
+#endif
 
 	ret
 #endif /* CONFIG_MMU */
@@ -174,6 +187,8 @@ secondary_start_common:
 	/* Enable virtual memory and relocate to virtual address */
 	la a0, swapper_pg_dir
 	XIP_FIXUP_OFFSET a0
+	la a1, kernel_map
+	REG_L a1, KERNEL_MAP_VIRT_ADDR(a1)
 	call relocate
 #endif
 	call setup_trap_vector
@@ -280,7 +295,25 @@ pmp_done:
 	mv a0, s0
 #endif
 
-#ifndef CONFIG_XIP_KERNEL
+	/* Save hart ID and DTB physical address */
+	mv s0, a0
+	mv s1, a1
+
+#ifdef CONFIG_XIP_KERNEL
+	/* Keep DTB physical address before switching to virtual addressing */
+	la s2, __dtb_start
+	/* No need to fixup early_pg_dir as it is read-only */
+	la a0, early_pg_dir
+	li a1, KERNEL_LINK_ADDR
+	call relocate
+#ifdef CONFIG_BUILTIN_DTB
+	mv a0, s2
+#else
+	mv a0, s1
+#endif /* CONFIG_BUILTIN_DTB */
+	la sp, init_thread_union + THREAD_SIZE
+	call setup_vm
+#else /* CONFIG_XIP_KERNEL */
 	/* Clear BSS for flat non-ELF images */
 	la a3, __bss_start
 	la a4, __bss_stop
@@ -290,18 +323,8 @@ clear_bss:
 	add a3, a3, RISCV_SZPTR
 	blt a3, a4, clear_bss
 clear_bss_done:
-#endif
-	/* Save hart ID and DTB physical address */
-	mv s0, a0
-	mv s1, a1
-
-	la a2, boot_cpu_hartid
-	XIP_FIXUP_OFFSET a2
-	REG_S a0, (a2)
-
 	/* Initialize page tables and relocate to virtual addresses */
 	la sp, init_thread_union + THREAD_SIZE
-	XIP_FIXUP_OFFSET sp
 #ifdef CONFIG_BUILTIN_DTB
 	la a0, __dtb_start
 #else
@@ -310,9 +333,14 @@ clear_bss_done:
 	call setup_vm
 #ifdef CONFIG_MMU
 	la a0, early_pg_dir
-	XIP_FIXUP_OFFSET a0
+	la a1, kernel_map
+	REG_L a1, KERNEL_MAP_VIRT_ADDR(a1)
 	call relocate
 #endif /* CONFIG_MMU */
+#endif /* CONFIG_XIP_KERNEL */
+
+	la a2, boot_cpu_hartid
+	REG_S s0, (a2)
 
 	call setup_trap_vector
 	/* Restore C environment */
diff --git a/arch/riscv/kernel/setup.c b/arch/riscv/kernel/setup.c
index 18bd0e4bc36c..19b416900f68 100644
--- a/arch/riscv/kernel/setup.c
+++ b/arch/riscv/kernel/setup.c
@@ -276,7 +276,7 @@ void __init setup_arch(char **cmdline_p)
 #if IS_ENABLED(CONFIG_BUILTIN_DTB)
 	unflatten_and_copy_device_tree();
 #else
-	if (early_init_dt_verify(__va(XIP_FIXUP(dtb_early_pa))))
+	if (early_init_dt_verify(__va(dtb_early_pa)))
 		unflatten_device_tree();
 	else
 		pr_err("No DTB found in kernel mappings\n");
diff --git a/arch/riscv/kernel/vmlinux-xip.lds.S b/arch/riscv/kernel/vmlinux-xip.lds.S
index af776555ded9..6aba03f3eadf 100644
--- a/arch/riscv/kernel/vmlinux-xip.lds.S
+++ b/arch/riscv/kernel/vmlinux-xip.lds.S
@@ -77,6 +77,9 @@ SECTIONS
 	}
 	__end_ro_after_init = .;
 
+	. = ALIGN(PAGE_SIZE);
+#include "early-page-table.lds.S"
+
 	. = ALIGN(PAGE_SIZE);
 	__init_begin = .;
 	.init.data : {
diff --git a/arch/riscv/mm/init.c b/arch/riscv/mm/init.c
index e2c8f188ad95..d5098b366274 100644
--- a/arch/riscv/mm/init.c
+++ b/arch/riscv/mm/init.c
@@ -32,9 +32,6 @@
 
 struct kernel_mapping kernel_map __ro_after_init;
 EXPORT_SYMBOL(kernel_map);
-#ifdef CONFIG_XIP_KERNEL
-#define kernel_map	(*(struct kernel_mapping *)XIP_FIXUP(&kernel_map))
-#endif
 
 phys_addr_t phys_ram_base __ro_after_init;
 EXPORT_SYMBOL(phys_ram_base);
@@ -49,8 +46,8 @@ EXPORT_SYMBOL(empty_zero_page);
 
 extern char _start[];
 #define DTB_EARLY_BASE_VA      PGDIR_SIZE
-void *_dtb_early_va __initdata;
-uintptr_t _dtb_early_pa __initdata;
+void *dtb_early_va __initdata;
+uintptr_t dtb_early_pa __initdata;
 
 struct pt_alloc_ops {
 	pte_t *(*get_pte_virt)(phys_addr_t pa);
@@ -212,29 +209,22 @@ static void __init setup_bootmem(void)
 }
 
 #ifdef CONFIG_MMU
-static struct pt_alloc_ops _pt_ops __initdata;
-
-#ifdef CONFIG_XIP_KERNEL
-#define pt_ops (*(struct pt_alloc_ops *)XIP_FIXUP(&_pt_ops))
-#else
-#define pt_ops _pt_ops
-#endif
+static struct pt_alloc_ops pt_ops __initdata;
 
 unsigned long pfn_base __ro_after_init;
 EXPORT_SYMBOL(pfn_base);
 
 pgd_t swapper_pg_dir[PTRS_PER_PGD] __page_aligned_bss;
 pgd_t trampoline_pg_dir[PTRS_PER_PGD] __page_aligned_bss;
+#ifdef CONFIG_XIP_KERNEL
+extern pte_t fixmap_pte[PTRS_PER_PTE];
+extern pgd_t early_pg_dir[PTRS_PER_PGD];
+#else
 static pte_t fixmap_pte[PTRS_PER_PTE] __page_aligned_bss;
-
 pgd_t early_pg_dir[PTRS_PER_PGD] __initdata __aligned(PAGE_SIZE);
-static pmd_t __maybe_unused early_dtb_pmd[PTRS_PER_PMD] __initdata __aligned(PAGE_SIZE);
+#endif
 
-#ifdef CONFIG_XIP_KERNEL
-#define trampoline_pg_dir      ((pgd_t *)XIP_FIXUP(trampoline_pg_dir))
-#define fixmap_pte             ((pte_t *)XIP_FIXUP(fixmap_pte))
-#define early_pg_dir           ((pgd_t *)XIP_FIXUP(early_pg_dir))
-#endif /* CONFIG_XIP_KERNEL */
+static pmd_t __maybe_unused early_dtb_pmd[PTRS_PER_PMD] __initdata __aligned(PAGE_SIZE);
 
 void __set_fixmap(enum fixed_addresses idx, phys_addr_t phys, pgprot_t prot)
 {
@@ -306,17 +296,16 @@ static void __init create_pte_mapping(pte_t *ptep,
 
 #ifndef __PAGETABLE_PMD_FOLDED
 
+#ifdef CONFIG_XIP_KERNEL
+extern pmd_t fixmap_pmd[PTRS_PER_PMD];
+extern pmd_t early_pmd[PTRS_PER_PMD];
+#else
 static pmd_t trampoline_pmd[PTRS_PER_PMD] __page_aligned_bss;
 static pmd_t fixmap_pmd[PTRS_PER_PMD] __page_aligned_bss;
 static pmd_t early_pmd[PTRS_PER_PMD] __initdata __aligned(PAGE_SIZE);
+#endif
 
-#ifdef CONFIG_XIP_KERNEL
-#define trampoline_pmd ((pmd_t *)XIP_FIXUP(trampoline_pmd))
-#define fixmap_pmd     ((pmd_t *)XIP_FIXUP(fixmap_pmd))
-#define early_pmd      ((pmd_t *)XIP_FIXUP(early_pmd))
-#endif /* CONFIG_XIP_KERNEL */
-
-static pmd_t *__init get_pmd_virt_early(phys_addr_t pa)
+static __maybe_unused pmd_t *__init get_pmd_virt_early(phys_addr_t pa)
 {
 	/* Before MMU is enabled */
 	return (pmd_t *)((uintptr_t)pa);
@@ -333,7 +322,7 @@ static pmd_t *__init get_pmd_virt_late(phys_addr_t pa)
 	return (pmd_t *) __va(pa);
 }
 
-static phys_addr_t __init alloc_pmd_early(uintptr_t va)
+static __maybe_unused phys_addr_t __init alloc_pmd_early(uintptr_t va)
 {
 	BUG_ON((va - kernel_map.virt_addr) >> PGDIR_SHIFT);
 
@@ -521,6 +510,14 @@ static void __init create_kernel_page_table(pgd_t *pgdir,
 				   kernel_map.phys_addr + (va - (kernel_map.virt_addr + XIP_OFFSET)),
 				   PMD_SIZE, PAGE_KERNEL);
 }
+
+static void __init setup_early_page_table(uintptr_t dtb_pa)
+{
+	/*
+	 * Nothing must be done here since the early page table is generated at
+	 * compile-time.
+	*/
+}
 #else
 static void __init create_kernel_page_table(pgd_t *pgdir, bool early)
 {
@@ -534,7 +531,6 @@ static void __init create_kernel_page_table(pgd_t *pgdir, bool early)
 				   early ?
 					PAGE_KERNEL_EXEC : pgprot_from_va(va));
 }
-#endif
 
 /*
  * Setup a 4MB mapping that encompasses the device tree: for 64-bit kernel,
@@ -557,20 +553,48 @@ static void __init create_fdt_early_page_table(pgd_t *pgdir, uintptr_t dtb_pa)
 		create_pmd_mapping(early_dtb_pmd, DTB_EARLY_BASE_VA + PMD_SIZE,
 				   pa + PMD_SIZE, PMD_SIZE, PAGE_KERNEL);
 	}
+#endif
+}
 
-	dtb_early_va = (void *)DTB_EARLY_BASE_VA + (dtb_pa & (PMD_SIZE - 1));
+static void __init setup_early_page_table(uintptr_t dtb_pa)
+{
+	pt_ops.alloc_pte = alloc_pte_early;
+	pt_ops.get_pte_virt = get_pte_virt_early;
+#ifndef __PAGETABLE_PMD_FOLDED
+	pt_ops.alloc_pmd = alloc_pmd_early;
+	pt_ops.get_pmd_virt = get_pmd_virt_early;
+#endif
+	/* Setup early PGD for fixmap */
+	create_pgd_mapping(early_pg_dir, FIXADDR_START,
+			   (uintptr_t)fixmap_pgd_next, PGDIR_SIZE, PAGE_TABLE);
+
+#ifndef __PAGETABLE_PMD_FOLDED
+	/* Setup fixmap PMD */
+	create_pmd_mapping(fixmap_pmd, FIXADDR_START,
+			   (uintptr_t)fixmap_pte, PMD_SIZE, PAGE_TABLE);
+	/* Setup trampoline PGD and PMD */
+	create_pgd_mapping(trampoline_pg_dir, kernel_map.virt_addr,
+			   (uintptr_t)trampoline_pmd, PGDIR_SIZE, PAGE_TABLE);
+
+	create_pmd_mapping(trampoline_pmd, kernel_map.virt_addr,
+			   kernel_map.phys_addr, PMD_SIZE, PAGE_KERNEL_EXEC);
 #else
+	/* Setup trampoline PGD */
+	create_pgd_mapping(trampoline_pg_dir, kernel_map.virt_addr,
+			   kernel_map.phys_addr, PGDIR_SIZE, PAGE_KERNEL_EXEC);
+#endif
+
 	/*
-	 * For 64-bit kernel, __va can't be used since it would return a linear
-	 * mapping address whereas dtb_early_va will be used before
-	 * setup_vm_final installs the linear mapping. For 32-bit kernel, as the
-	 * kernel is mapped in the linear mapping, that makes no difference.
+	 * Setup early PGD covering entire kernel which will allow
+	 * us to reach paging_init(). We map all memory banks later
+	 * in setup_vm_final() below.
 	 */
-	dtb_early_va = kernel_mapping_pa_to_va(XIP_FIXUP(dtb_pa));
-#endif
+	create_kernel_page_table(early_pg_dir, true);
 
-	dtb_early_pa = dtb_pa;
+	/* Setup early mapping for FDT early scan */
+	create_fdt_early_page_table(early_pg_dir, dtb_pa);
 }
+#endif
 
 asmlinkage void __init setup_vm(uintptr_t dtb_pa)
 {
@@ -600,45 +624,21 @@ asmlinkage void __init setup_vm(uintptr_t dtb_pa)
 	BUG_ON((PAGE_OFFSET % PGDIR_SIZE) != 0);
 	BUG_ON((kernel_map.phys_addr % PMD_SIZE) != 0);
 
-	pt_ops.alloc_pte = alloc_pte_early;
-	pt_ops.get_pte_virt = get_pte_virt_early;
-#ifndef __PAGETABLE_PMD_FOLDED
-	pt_ops.alloc_pmd = alloc_pmd_early;
-	pt_ops.get_pmd_virt = get_pmd_virt_early;
-#endif
-	/* Setup early PGD for fixmap */
-	create_pgd_mapping(early_pg_dir, FIXADDR_START,
-			   (uintptr_t)fixmap_pgd_next, PGDIR_SIZE, PAGE_TABLE);
+	setup_early_page_table(dtb_pa);
 
-#ifndef __PAGETABLE_PMD_FOLDED
-	/* Setup fixmap PMD */
-	create_pmd_mapping(fixmap_pmd, FIXADDR_START,
-			   (uintptr_t)fixmap_pte, PMD_SIZE, PAGE_TABLE);
-	/* Setup trampoline PGD and PMD */
-	create_pgd_mapping(trampoline_pg_dir, kernel_map.virt_addr,
-			   (uintptr_t)trampoline_pmd, PGDIR_SIZE, PAGE_TABLE);
-#ifdef CONFIG_XIP_KERNEL
-	create_pmd_mapping(trampoline_pmd, kernel_map.virt_addr,
-			   kernel_map.xiprom, PMD_SIZE, PAGE_KERNEL_EXEC);
-#else
-	create_pmd_mapping(trampoline_pmd, kernel_map.virt_addr,
-			   kernel_map.phys_addr, PMD_SIZE, PAGE_KERNEL_EXEC);
-#endif
+#ifndef CONFIG_BUILTIN_DTB
+	dtb_early_va = (void *)DTB_EARLY_BASE_VA + (dtb_pa & (PMD_SIZE - 1));
 #else
-	/* Setup trampoline PGD */
-	create_pgd_mapping(trampoline_pg_dir, kernel_map.virt_addr,
-			   kernel_map.phys_addr, PGDIR_SIZE, PAGE_KERNEL_EXEC);
-#endif
-
 	/*
-	 * Setup early PGD covering entire kernel which will allow
-	 * us to reach paging_init(). We map all memory banks later
-	 * in setup_vm_final() below.
+	 * For 64-bit kernel, __va can't be used since it would return a linear
+	 * mapping address whereas dtb_early_va will be used before
+	 * setup_vm_final installs the linear mapping. For 32-bit kernel, as the
+	 * kernel is mapped in the linear mapping, that makes no difference.
 	 */
-	create_kernel_page_table(early_pg_dir, true);
+	dtb_early_va = kernel_mapping_pa_to_va(dtb_pa);
+#endif
 
-	/* Setup early mapping for FDT early scan */
-	create_fdt_early_page_table(early_pg_dir, dtb_pa);
+	dtb_early_pa = dtb_pa;
 
 	/*
 	 * Bootime fixmap only can handle PMD_SIZE mapping. Thus, boot-ioremap
-- 
2.30.2


^ permalink raw reply	[flat|nested] 2+ messages in thread

end of thread, other threads:[~2021-08-25  5:09 UTC | newest]

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2021-08-05  9:55 [PATCH RFC] riscv: Introduce compile-time early page table for XIP kernel Alexandre Ghiti
2021-08-25  5:09 ` Palmer Dabbelt

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