RISC-V: Fixmap support and MM cleanups

This patchset does:
1. Moves MM related code from kernel/setup.c to mm/init.c
2. Implements compile-time fixed mappings

Using fixed mappings, we get earlyprints even without SBI calls.

For example, we can now use kernel parameter
"earlycon=uart8250,mmio,0x10000000"
to get early prints on QEMU virt machine without using SBI calls.

The patchset is tested on QEMU virt machine.

Palmer: It looks like some of the code movement here conflicted with the
patches to move hartid handling around.  As far as I can tell the only
changed code was in smp_setup_processor_id(), and I've kept the one in
smp.c.

arch/riscv/Kconfig

@@ -89,6 +89,9 @@ config GENERIC_CSUM
 config GENERIC_HWEIGHT
 	def_bool y
 
+config FIX_EARLYCON_MEM
+	def_bool y
+
 config PGTABLE_LEVELS
 	int
 	default 3 if 64BIT

arch/riscv/include/asm/fixmap.h

@@ -0,0 +1,44 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Copyright (C) 2019 Western Digital Corporation or its affiliates.
+ */
+
+#ifndef _ASM_RISCV_FIXMAP_H
+#define _ASM_RISCV_FIXMAP_H
+
+#include <linux/kernel.h>
+#include <linux/sizes.h>
+#include <asm/page.h>
+#include <asm/pgtable.h>
+
+/*
+ * Here we define all the compile-time 'special' virtual addresses.
+ * The point is to have a constant address at compile time, but to
+ * set the physical address only in the boot process.
+ *
+ * These 'compile-time allocated' memory buffers are page-sized. Use
+ * set_fixmap(idx,phys) to associate physical memory with fixmap indices.
+ */
+enum fixed_addresses {
+	FIX_HOLE,
+	FIX_EARLYCON_MEM_BASE,
+	__end_of_fixed_addresses
+};
+
+#define FIXADDR_SIZE		(__end_of_fixed_addresses * PAGE_SIZE)
+#define FIXADDR_TOP		(PAGE_OFFSET)
+#define FIXADDR_START		(FIXADDR_TOP - FIXADDR_SIZE)
+
+#define FIXMAP_PAGE_IO		PAGE_KERNEL
+
+#define __early_set_fixmap	__set_fixmap
+
+#define __late_set_fixmap	__set_fixmap
+#define __late_clear_fixmap(idx) __set_fixmap((idx), 0, FIXMAP_PAGE_CLEAR)
+
+extern void __set_fixmap(enum fixed_addresses idx,
+			 phys_addr_t phys, pgprot_t prot);
+
+#include <asm-generic/fixmap.h>
+
+#endif /* _ASM_RISCV_FIXMAP_H */

arch/riscv/include/asm/pgtable.h

@@ -404,6 +404,7 @@ static inline int ptep_clear_flush_young(struct vm_area_struct *vma,
 #define kern_addr_valid(addr)   (1) /* FIXME */
 #endif
 
+extern void setup_bootmem(void);
 extern void paging_init(void);
 
 static inline void pgtable_cache_init(void)

arch/riscv/kernel/setup.c

@@ -23,7 +23,6 @@
 #include <linux/mm.h>
 #include <linux/memblock.h>
 #include <linux/sched.h>
-#include <linux/initrd.h>
 #include <linux/console.h>
 #include <linux/screen_info.h>
 #include <linux/of_fdt.h>
@@ -61,83 +60,6 @@ EXPORT_SYMBOL(empty_zero_page);
 atomic_t hart_lottery;
 unsigned long boot_cpu_hartid;
 
-#ifdef CONFIG_BLK_DEV_INITRD
-static void __init setup_initrd(void)
-{
-	unsigned long size;
-
-	if (initrd_start >= initrd_end) {
-		pr_info("initrd not found or empty");
-		goto disable;
-	}
-	if (__pa(initrd_end) > PFN_PHYS(max_low_pfn)) {
-		pr_err("initrd extends beyond end of memory");
-		goto disable;
-	}
-
-	size =  initrd_end - initrd_start;
-	memblock_reserve(__pa(initrd_start), size);
-	initrd_below_start_ok = 1;
-
-	pr_info("Initial ramdisk at: 0x%p (%lu bytes)\n",
-		(void *)(initrd_start), size);
-	return;
-disable:
-	pr_cont(" - disabling initrd\n");
-	initrd_start = 0;
-	initrd_end = 0;
-}
-#endif /* CONFIG_BLK_DEV_INITRD */
-
-pgd_t swapper_pg_dir[PTRS_PER_PGD] __page_aligned_bss;
-pgd_t trampoline_pg_dir[PTRS_PER_PGD] __initdata __aligned(PAGE_SIZE);
-
-#ifndef __PAGETABLE_PMD_FOLDED
-#define NUM_SWAPPER_PMDS ((uintptr_t)-PAGE_OFFSET >> PGDIR_SHIFT)
-pmd_t swapper_pmd[PTRS_PER_PMD*((-PAGE_OFFSET)/PGDIR_SIZE)] __page_aligned_bss;
-pmd_t trampoline_pmd[PTRS_PER_PGD] __initdata __aligned(PAGE_SIZE);
-#endif
-
-asmlinkage void __init setup_vm(void)
-{
-	extern char _start;
-	uintptr_t i;
-	uintptr_t pa = (uintptr_t) &_start;
-	pgprot_t prot = __pgprot(pgprot_val(PAGE_KERNEL) | _PAGE_EXEC);
-
-	va_pa_offset = PAGE_OFFSET - pa;
-	pfn_base = PFN_DOWN(pa);
-
-	/* Sanity check alignment and size */
-	BUG_ON((PAGE_OFFSET % PGDIR_SIZE) != 0);
-	BUG_ON((pa % (PAGE_SIZE * PTRS_PER_PTE)) != 0);
-
-#ifndef __PAGETABLE_PMD_FOLDED
-	trampoline_pg_dir[(PAGE_OFFSET >> PGDIR_SHIFT) % PTRS_PER_PGD] =
-		pfn_pgd(PFN_DOWN((uintptr_t)trampoline_pmd),
-			__pgprot(_PAGE_TABLE));
-	trampoline_pmd[0] = pfn_pmd(PFN_DOWN(pa), prot);
-
-	for (i = 0; i < (-PAGE_OFFSET)/PGDIR_SIZE; ++i) {
-		size_t o = (PAGE_OFFSET >> PGDIR_SHIFT) % PTRS_PER_PGD + i;
-		swapper_pg_dir[o] =
-			pfn_pgd(PFN_DOWN((uintptr_t)swapper_pmd) + i,
-				__pgprot(_PAGE_TABLE));
-	}
-	for (i = 0; i < ARRAY_SIZE(swapper_pmd); i++)
-		swapper_pmd[i] = pfn_pmd(PFN_DOWN(pa + i * PMD_SIZE), prot);
-#else
-	trampoline_pg_dir[(PAGE_OFFSET >> PGDIR_SHIFT) % PTRS_PER_PGD] =
-		pfn_pgd(PFN_DOWN(pa), prot);
-
-	for (i = 0; i < (-PAGE_OFFSET)/PGDIR_SIZE; ++i) {
-		size_t o = (PAGE_OFFSET >> PGDIR_SHIFT) % PTRS_PER_PGD + i;
-		swapper_pg_dir[o] =
-			pfn_pgd(PFN_DOWN(pa + i * PGDIR_SIZE), prot);
-	}
-#endif
-}
-
 void __init parse_dtb(unsigned int hartid, void *dtb)
 {
 	if (early_init_dt_scan(__va(dtb)))
@@ -150,60 +72,17 @@ void __init parse_dtb(unsigned int hartid, void *dtb)
 #endif
 }
 
-static void __init setup_bootmem(void)
-{
-	struct memblock_region *reg;
-	phys_addr_t mem_size = 0;
-
-	/* Find the memory region containing the kernel */
-	for_each_memblock(memory, reg) {
-		phys_addr_t vmlinux_end = __pa(_end);
-		phys_addr_t end = reg->base + reg->size;
-
-		if (reg->base <= vmlinux_end && vmlinux_end <= end) {
-			/*
-			 * Reserve from the start of the region to the end of
-			 * the kernel
-			 */
-			memblock_reserve(reg->base, vmlinux_end - reg->base);
-			mem_size = min(reg->size, (phys_addr_t)-PAGE_OFFSET);
-		}
-	}
-	BUG_ON(mem_size == 0);
-
-	set_max_mapnr(PFN_DOWN(mem_size));
-	max_low_pfn = PFN_DOWN(memblock_end_of_DRAM());
-
-#ifdef CONFIG_BLK_DEV_INITRD
-	setup_initrd();
-#endif /* CONFIG_BLK_DEV_INITRD */
-
-	early_init_fdt_reserve_self();
-	early_init_fdt_scan_reserved_mem();
-	memblock_allow_resize();
-	memblock_dump_all();
-
-	for_each_memblock(memory, reg) {
-		unsigned long start_pfn = memblock_region_memory_base_pfn(reg);
-		unsigned long end_pfn = memblock_region_memory_end_pfn(reg);
-
-		memblock_set_node(PFN_PHYS(start_pfn),
-		                  PFN_PHYS(end_pfn - start_pfn),
-		                  &memblock.memory, 0);
-	}
-}
-
 void __init setup_arch(char **cmdline_p)
 {
-	*cmdline_p = boot_command_line;
-
-	parse_early_param();
-
 	init_mm.start_code = (unsigned long) _stext;
 	init_mm.end_code   = (unsigned long) _etext;
 	init_mm.end_data   = (unsigned long) _edata;
 	init_mm.brk        = (unsigned long) _end;
 
+	*cmdline_p = boot_command_line;
+
+	parse_early_param();
+
 	setup_bootmem();
 	paging_init();
 	unflatten_device_tree();
@@ -222,4 +101,3 @@ void __init setup_arch(char **cmdline_p)
 
 	riscv_fill_hwcap();
 }
-

arch/riscv/kernel/smp.c

@@ -42,7 +42,7 @@ unsigned long __cpuid_to_hartid_map[NR_CPUS] = {
 
 void __init smp_setup_processor_id(void)
 {
-	cpuid_to_hartid_map(0) = boot_cpu_hartid;
+       cpuid_to_hartid_map(0) = boot_cpu_hartid;
 }
 
 /* A collection of single bit ipi messages.  */

arch/riscv/mm/init.c

@@ -17,7 +17,9 @@
 #include <linux/initrd.h>
 #include <linux/swap.h>
 #include <linux/sizes.h>
+#include <linux/of_fdt.h>
 
+#include <asm/fixmap.h>
 #include <asm/tlbflush.h>
 #include <asm/sections.h>
 #include <asm/pgtable.h>
@@ -66,7 +68,159 @@ void free_initmem(void)
 }
 
 #ifdef CONFIG_BLK_DEV_INITRD
-void free_initrd_mem(unsigned long start, unsigned long end)
+static void __init setup_initrd(void)
 {
+	unsigned long size;
+
+	if (initrd_start >= initrd_end) {
+		pr_info("initrd not found or empty");
+		goto disable;
+	}
+	if (__pa(initrd_end) > PFN_PHYS(max_low_pfn)) {
+		pr_err("initrd extends beyond end of memory");
+		goto disable;
+	}
+
+	size = initrd_end - initrd_start;
+	memblock_reserve(__pa(initrd_start), size);
+	initrd_below_start_ok = 1;
+
+	pr_info("Initial ramdisk at: 0x%p (%lu bytes)\n",
+		(void *)(initrd_start), size);
+	return;
+disable:
+	pr_cont(" - disabling initrd\n");
+	initrd_start = 0;
+	initrd_end = 0;
+}
+
+void __init free_initrd_mem(unsigned long start, unsigned long end)
+{
+	free_reserved_area((void *)start, (void *)end, -1, "initrd");
 }
 #endif /* CONFIG_BLK_DEV_INITRD */
+
+void __init setup_bootmem(void)
+{
+	struct memblock_region *reg;
+	phys_addr_t mem_size = 0;
+
+	/* Find the memory region containing the kernel */
+	for_each_memblock(memory, reg) {
+		phys_addr_t vmlinux_end = __pa(_end);
+		phys_addr_t end = reg->base + reg->size;
+
+		if (reg->base <= vmlinux_end && vmlinux_end <= end) {
+			/*
+			 * Reserve from the start of the region to the end of
+			 * the kernel
+			 */
+			memblock_reserve(reg->base, vmlinux_end - reg->base);
+			mem_size = min(reg->size, (phys_addr_t)-PAGE_OFFSET);
+		}
+	}
+	BUG_ON(mem_size == 0);
+
+	set_max_mapnr(PFN_DOWN(mem_size));
+	max_low_pfn = PFN_DOWN(memblock_end_of_DRAM());
+
+#ifdef CONFIG_BLK_DEV_INITRD
+	setup_initrd();
+#endif /* CONFIG_BLK_DEV_INITRD */
+
+	early_init_fdt_reserve_self();
+	early_init_fdt_scan_reserved_mem();
+	memblock_allow_resize();
+	memblock_dump_all();
+
+	for_each_memblock(memory, reg) {
+		unsigned long start_pfn = memblock_region_memory_base_pfn(reg);
+		unsigned long end_pfn = memblock_region_memory_end_pfn(reg);
+
+		memblock_set_node(PFN_PHYS(start_pfn),
+				  PFN_PHYS(end_pfn - start_pfn),
+				  &memblock.memory, 0);
+	}
+}
+
+pgd_t swapper_pg_dir[PTRS_PER_PGD] __page_aligned_bss;
+pgd_t trampoline_pg_dir[PTRS_PER_PGD] __initdata __aligned(PAGE_SIZE);
+
+#ifndef __PAGETABLE_PMD_FOLDED
+#define NUM_SWAPPER_PMDS ((uintptr_t)-PAGE_OFFSET >> PGDIR_SHIFT)
+pmd_t swapper_pmd[PTRS_PER_PMD*((-PAGE_OFFSET)/PGDIR_SIZE)] __page_aligned_bss;
+pmd_t trampoline_pmd[PTRS_PER_PGD] __initdata __aligned(PAGE_SIZE);
+pmd_t fixmap_pmd[PTRS_PER_PMD] __page_aligned_bss;
+#endif
+
+pte_t fixmap_pte[PTRS_PER_PTE] __page_aligned_bss;
+
+void __set_fixmap(enum fixed_addresses idx, phys_addr_t phys, pgprot_t prot)
+{
+	unsigned long addr = __fix_to_virt(idx);
+	pte_t *ptep;
+
+	BUG_ON(idx <= FIX_HOLE || idx >= __end_of_fixed_addresses);
+
+	ptep = &fixmap_pte[pte_index(addr)];
+
+	if (pgprot_val(prot)) {
+		set_pte(ptep, pfn_pte(phys >> PAGE_SHIFT, prot));
+	} else {
+		pte_clear(&init_mm, addr, ptep);
+		local_flush_tlb_page(addr);
+	}
+}
+
+asmlinkage void __init setup_vm(void)
+{
+	extern char _start;
+	uintptr_t i;
+	uintptr_t pa = (uintptr_t) &_start;
+	pgprot_t prot = __pgprot(pgprot_val(PAGE_KERNEL) | _PAGE_EXEC);
+
+	va_pa_offset = PAGE_OFFSET - pa;
+	pfn_base = PFN_DOWN(pa);
+
+	/* Sanity check alignment and size */
+	BUG_ON((PAGE_OFFSET % PGDIR_SIZE) != 0);
+	BUG_ON((pa % (PAGE_SIZE * PTRS_PER_PTE)) != 0);
+
+#ifndef __PAGETABLE_PMD_FOLDED
+	trampoline_pg_dir[(PAGE_OFFSET >> PGDIR_SHIFT) % PTRS_PER_PGD] =
+		pfn_pgd(PFN_DOWN((uintptr_t)trampoline_pmd),
+			__pgprot(_PAGE_TABLE));
+	trampoline_pmd[0] = pfn_pmd(PFN_DOWN(pa), prot);
+
+	for (i = 0; i < (-PAGE_OFFSET)/PGDIR_SIZE; ++i) {
+		size_t o = (PAGE_OFFSET >> PGDIR_SHIFT) % PTRS_PER_PGD + i;
+
+		swapper_pg_dir[o] =
+			pfn_pgd(PFN_DOWN((uintptr_t)swapper_pmd) + i,
+				__pgprot(_PAGE_TABLE));
+	}
+	for (i = 0; i < ARRAY_SIZE(swapper_pmd); i++)
+		swapper_pmd[i] = pfn_pmd(PFN_DOWN(pa + i * PMD_SIZE), prot);
+
+	swapper_pg_dir[(FIXADDR_START >> PGDIR_SHIFT) % PTRS_PER_PGD] =
+		pfn_pgd(PFN_DOWN((uintptr_t)fixmap_pmd),
+				__pgprot(_PAGE_TABLE));
+	fixmap_pmd[(FIXADDR_START >> PMD_SHIFT) % PTRS_PER_PMD] =
+		pfn_pmd(PFN_DOWN((uintptr_t)fixmap_pte),
+				__pgprot(_PAGE_TABLE));
+#else
+	trampoline_pg_dir[(PAGE_OFFSET >> PGDIR_SHIFT) % PTRS_PER_PGD] =
+		pfn_pgd(PFN_DOWN(pa), prot);
+
+	for (i = 0; i < (-PAGE_OFFSET)/PGDIR_SIZE; ++i) {
+		size_t o = (PAGE_OFFSET >> PGDIR_SHIFT) % PTRS_PER_PGD + i;
+
+		swapper_pg_dir[o] =
+			pfn_pgd(PFN_DOWN(pa + i * PGDIR_SIZE), prot);
+	}
+
+	swapper_pg_dir[(FIXADDR_START >> PGDIR_SHIFT) % PTRS_PER_PGD] =
+		pfn_pgd(PFN_DOWN((uintptr_t)fixmap_pte),
+				__pgprot(_PAGE_TABLE));
+#endif
+}