Currently, we have to boot RISCV64 kernel from a 2MB aligned physical address and RISCV32 kernel from a 4MB aligned physical address. This constraint is because initial pagetable setup (i.e. setup_vm()) maps entire RAM using hugepages (i.e. 2MB for 3-level pagetable and 4MB for 2-level pagetable).
Further, the above booting contraint also results in memory wastage because if we boot kernel from some <xyz> address (which is not same as RAM start address) then RISCV kernel will map PAGE_OFFSET virtual address lineraly to <xyz> physical address and memory between RAM start and <xyz> will be reserved/unusable. For example, RISCV64 kernel booted from 0x80200000 will waste 2MB of RAM and RISCV32 kernel booted from 0x80400000 will waste 4MB of RAM. This patch re-writes the initial pagetable setup code to allow booting RISV32 and RISCV64 kernel from any 4KB (i.e. PAGE_SIZE) aligned address. To achieve this: 1. We add kconfig option BOOT_PAGE_ALIGNED. When it is enabled we use 4KB mappings in initial page table setup otherwise we use 2MB/4MB mappings. 2. We map kernel and dtb (few MBs) in setup_vm() (called from head.S) 3. Once we reach paging_init() (called from setup_arch()) after memblock setup, we map all available memory banks. With this patch in-place, the booting constraint for RISCV32 and RISCV64 kernel is much more relaxed when CONFIG_BOOT_PAGE_ALIGNED=y and we can now boot kernel very close to RAM start thereby minimizng memory wastage. Signed-off-by: Anup Patel <[email protected]> --- arch/riscv/Kconfig | 12 + arch/riscv/include/asm/fixmap.h | 5 + arch/riscv/include/asm/pgtable-64.h | 5 + arch/riscv/include/asm/pgtable.h | 5 + arch/riscv/kernel/head.S | 1 + arch/riscv/kernel/setup.c | 4 +- arch/riscv/mm/init.c | 351 ++++++++++++++++++++++++---- 7 files changed, 335 insertions(+), 48 deletions(-) diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig index eb56c82d8aa1..d7812b1f7c7e 100644 --- a/arch/riscv/Kconfig +++ b/arch/riscv/Kconfig @@ -172,6 +172,18 @@ config SMP If you don't know what to do here, say N. +config BOOT_PAGE_ALIGNED + bool "Allow booting from page aligned address" + default n + help + This enables support for booting the kernel from any page aligned + address (i.e. 4KB aligned). This option is particularly useful on + systems with a very small RAM (few MBs) as we can boot the kernel + closer to the RAM start address, thereby reducing the amount of + unusable RAM below the kernel. + + If you don't know what to do here, say N. + config NR_CPUS int "Maximum number of CPUs (2-32)" range 2 32 diff --git a/arch/riscv/include/asm/fixmap.h b/arch/riscv/include/asm/fixmap.h index c207f6634b91..9c66033c3a54 100644 --- a/arch/riscv/include/asm/fixmap.h +++ b/arch/riscv/include/asm/fixmap.h @@ -21,6 +21,11 @@ */ enum fixed_addresses { FIX_HOLE, +#define FIX_FDT_SIZE SZ_1M + FIX_FDT_END, + FIX_FDT = FIX_FDT_END + FIX_FDT_SIZE / PAGE_SIZE - 1, + FIX_PTE, + FIX_PMD, FIX_EARLYCON_MEM_BASE, __end_of_fixed_addresses }; diff --git a/arch/riscv/include/asm/pgtable-64.h b/arch/riscv/include/asm/pgtable-64.h index 7aa0ea9bd8bb..56ecc3dc939d 100644 --- a/arch/riscv/include/asm/pgtable-64.h +++ b/arch/riscv/include/asm/pgtable-64.h @@ -78,6 +78,11 @@ static inline pmd_t pfn_pmd(unsigned long pfn, pgprot_t prot) return __pmd((pfn << _PAGE_PFN_SHIFT) | pgprot_val(prot)); } +static inline unsigned long _pmd_pfn(pmd_t pmd) +{ + return pmd_val(pmd) >> _PAGE_PFN_SHIFT; +} + #define pmd_ERROR(e) \ pr_err("%s:%d: bad pmd %016lx.\n", __FILE__, __LINE__, pmd_val(e)) diff --git a/arch/riscv/include/asm/pgtable.h b/arch/riscv/include/asm/pgtable.h index 1141364d990e..c4968b47c37d 100644 --- a/arch/riscv/include/asm/pgtable.h +++ b/arch/riscv/include/asm/pgtable.h @@ -127,6 +127,11 @@ static inline pgd_t pfn_pgd(unsigned long pfn, pgprot_t prot) return __pgd((pfn << _PAGE_PFN_SHIFT) | pgprot_val(prot)); } +static inline unsigned long _pgd_pfn(pgd_t pgd) +{ + return pgd_val(pgd) >> _PAGE_PFN_SHIFT; +} + #define pgd_index(addr) (((addr) >> PGDIR_SHIFT) & (PTRS_PER_PGD - 1)) /* Locate an entry in the page global directory */ diff --git a/arch/riscv/kernel/head.S b/arch/riscv/kernel/head.S index 3449671ec867..61e253ae38b4 100644 --- a/arch/riscv/kernel/head.S +++ b/arch/riscv/kernel/head.S @@ -62,6 +62,7 @@ clear_bss_done: /* Initialize page tables and relocate to virtual addresses */ la sp, init_thread_union + THREAD_SIZE + mv a0, s1 call setup_vm call relocate diff --git a/arch/riscv/kernel/setup.c b/arch/riscv/kernel/setup.c index 540a331d1376..79670458527d 100644 --- a/arch/riscv/kernel/setup.c +++ b/arch/riscv/kernel/setup.c @@ -30,6 +30,7 @@ #include <linux/sched/task.h> #include <linux/swiotlb.h> +#include <asm/fixmap.h> #include <asm/setup.h> #include <asm/sections.h> #include <asm/pgtable.h> @@ -54,7 +55,8 @@ unsigned long boot_cpu_hartid; void __init parse_dtb(unsigned int hartid, void *dtb) { - if (early_init_dt_scan(__va(dtb))) + dtb = (void *)fix_to_virt(FIX_FDT) + ((uintptr_t)dtb & ~PAGE_MASK); + if (early_init_dt_scan(dtb)) return; pr_err("No DTB passed to the kernel\n"); diff --git a/arch/riscv/mm/init.c b/arch/riscv/mm/init.c index f9add4381c73..56970dab3727 100644 --- a/arch/riscv/mm/init.c +++ b/arch/riscv/mm/init.c @@ -1,14 +1,7 @@ +/* SPDX-License-Identifier: GPL-2.0 */ /* * Copyright (C) 2012 Regents of the University of California - * - * This program is free software; you can redistribute it and/or - * modify it under the terms of the GNU General Public License - * as published by the Free Software Foundation, version 2. - * - * This program is distributed in the hope that it will be useful, - * but WITHOUT ANY WARRANTY; without even the implied warranty of - * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the - * GNU General Public License for more details. + * Copyright (C) 2019 Western Digital Corporation or its affiliates. */ #include <linux/init.h> @@ -49,13 +42,6 @@ void setup_zero_page(void) memset((void *)empty_zero_page, 0, PAGE_SIZE); } -void __init paging_init(void) -{ - setup_zero_page(); - local_flush_tlb_all(); - zone_sizes_init(); -} - void __init mem_init(void) { #ifdef CONFIG_FLATMEM @@ -152,16 +138,28 @@ EXPORT_SYMBOL(va_pa_offset); unsigned long pfn_base; EXPORT_SYMBOL(pfn_base); +#define MAX_EARLY_MAPPING_SIZE SZ_128M + pgd_t swapper_pg_dir[PTRS_PER_PGD] __page_aligned_bss; #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; +#if MAX_EARLY_MAPPING_SIZE < PGDIR_SIZE +#define NUM_SWAPPER_PMDS 1UL +#else +#define NUM_SWAPPER_PMDS (MAX_EARLY_MAPPING_SIZE/PGDIR_SIZE) +#endif +pmd_t swapper_pmd[PTRS_PER_PMD*NUM_SWAPPER_PMDS] __page_aligned_bss; pmd_t fixmap_pmd[PTRS_PER_PMD] __page_aligned_bss; +#define NUM_SWAPPER_PTES (MAX_EARLY_MAPPING_SIZE/PMD_SIZE) +#else +#define NUM_SWAPPER_PTES (MAX_EARLY_MAPPING_SIZE/PGDIR_SIZE) #endif +pte_t swapper_pte[PTRS_PER_PTE*NUM_SWAPPER_PTES] __page_aligned_bss; pte_t fixmap_pte[PTRS_PER_PTE] __page_aligned_bss; +static uintptr_t map_size; + void __set_fixmap(enum fixed_addresses idx, phys_addr_t phys, pgprot_t prot) { unsigned long addr = __fix_to_virt(idx); @@ -179,6 +177,201 @@ void __set_fixmap(enum fixed_addresses idx, phys_addr_t phys, pgprot_t prot) } } +struct mapping_ops { + pte_t *(*get_pte_virt)(phys_addr_t pa); + phys_addr_t (*alloc_pte)(uintptr_t va); + pmd_t *(*get_pmd_virt)(phys_addr_t pa); + phys_addr_t (*alloc_pmd)(uintptr_t va); +}; + +static phys_addr_t __init final_alloc_pgtable(void) +{ + return memblock_phys_alloc(PAGE_SIZE, PAGE_SIZE); +} + +static pte_t *__init early_get_pte_virt(phys_addr_t pa) +{ + return (pte_t *)((uintptr_t)pa); +} + +static pte_t *__init final_get_pte_virt(phys_addr_t pa) +{ + clear_fixmap(FIX_PTE); + + return (pte_t *)set_fixmap_offset(FIX_PTE, pa); +} + +static phys_addr_t __init early_alloc_pte(uintptr_t va) +{ + pte_t *base = swapper_pte; + uintptr_t pte_num = ((va - PAGE_OFFSET) >> PMD_SHIFT); + + BUG_ON(pte_num >= NUM_SWAPPER_PTES); + + return (uintptr_t)&base[pte_num * PTRS_PER_PTE]; +} + +static phys_addr_t __init final_alloc_pte(uintptr_t va) +{ + return final_alloc_pgtable(); +} + +static void __init create_pte_mapping(pte_t *ptep, + uintptr_t va, phys_addr_t pa, + phys_addr_t sz, pgprot_t prot) +{ + uintptr_t pte_index = pte_index(va); + + BUG_ON(sz != PAGE_SIZE); + + if (pte_none(ptep[pte_index])) + ptep[pte_index] = pfn_pte(PFN_DOWN(pa), prot); +} + +#ifndef __PAGETABLE_PMD_FOLDED +static pmd_t *__init early_get_pmd_virt(phys_addr_t pa) +{ + return (pmd_t *)((uintptr_t)pa); +} + +static pmd_t *__init final_get_pmd_virt(phys_addr_t pa) +{ + clear_fixmap(FIX_PMD); + + return (pmd_t *)set_fixmap_offset(FIX_PMD, pa); +} + +static phys_addr_t __init early_alloc_pmd(uintptr_t va) +{ + pmd_t *base = swapper_pmd; + uintptr_t pmd_num = (va - PAGE_OFFSET) >> PGDIR_SHIFT; + + BUG_ON(pmd_num >= NUM_SWAPPER_PMDS); + + return (uintptr_t)&base[pmd_num * PTRS_PER_PMD]; +} + +static phys_addr_t __init final_alloc_pmd(uintptr_t va) +{ + return final_alloc_pgtable(); +} + +static void __init create_pmd_mapping(pmd_t *pmdp, + uintptr_t va, phys_addr_t pa, + phys_addr_t sz, pgprot_t prot, + struct mapping_ops *ops) +{ + pte_t *ptep; + phys_addr_t pte_phys; + uintptr_t pmd_index = pmd_index(va); + + if (sz == PMD_SIZE) { + if (pmd_none(pmdp[pmd_index])) + pmdp[pmd_index] = pfn_pmd(PFN_DOWN(pa), prot); + return; + } + + if (pmd_none(pmdp[pmd_index])) { + pte_phys = ops->alloc_pte(va); + pmdp[pmd_index] = pfn_pmd(PFN_DOWN(pte_phys), + __pgprot(_PAGE_TABLE)); + ptep = ops->get_pte_virt(pte_phys); + memset(ptep, 0, PAGE_SIZE); + } else { + pte_phys = PFN_PHYS(_pmd_pfn(pmdp[pmd_index])); + ptep = ops->get_pte_virt(pte_phys); + } + + create_pte_mapping(ptep, va, pa, sz, prot); +} + + +static void __init create_pgd_mapping(pgd_t *pgdp, + uintptr_t va, phys_addr_t pa, + phys_addr_t sz, pgprot_t prot, + struct mapping_ops *ops) +{ + pmd_t *pmdp; + phys_addr_t pmd_phys; + uintptr_t pgd_index = pgd_index(va); + + if (sz == PGDIR_SIZE) { + if (pgd_val(pgdp[pgd_index]) == 0) + pgdp[pgd_index] = pfn_pgd(PFN_DOWN(pa), prot); + return; + } + + if (pgd_val(pgdp[pgd_index]) == 0) { + pmd_phys = ops->alloc_pmd(va); + pgdp[pgd_index] = pfn_pgd(PFN_DOWN(pmd_phys), + __pgprot(_PAGE_TABLE)); + pmdp = ops->get_pmd_virt(pmd_phys); + memset(pmdp, 0, PAGE_SIZE); + } else { + pmd_phys = PFN_PHYS(_pgd_pfn(pgdp[pgd_index])); + pmdp = ops->get_pmd_virt(pmd_phys); + } + + create_pmd_mapping(pmdp, va, pa, sz, prot, ops); +} +#else +static void __init create_pgd_mapping(pgd_t *pgdp, + uintptr_t va, phys_addr_t pa, + phys_addr_t sz, pgprot_t prot, + struct mapping_ops *ops) +{ + pte_t *ptep; + phys_addr_t pte_phys; + uintptr_t pgd_index = pgd_index(va); + + if (sz == PGDIR_SIZE) { + if (pgd_val(pgdp[pgd_index]) == 0) + pgdp[pgd_index] = pfn_pgd(PFN_DOWN(pa), prot); + return; + } + + if (pgd_val(pgdp[pgd_index]) == 0) { + pte_phys = ops->alloc_pte(va); + pgdp[pgd_index] = pfn_pgd(PFN_DOWN(pte_phys), + __pgprot(_PAGE_TABLE)); + ptep = ops->get_pte_virt(pte_phys); + memset(ptep, 0, PAGE_SIZE); + } else { + pte_phys = PFN_PHYS(_pgd_pfn(pgdp[pgd_index])); + ptep = ops->get_pte_virt(pte_phys); + } + + create_pte_mapping(ptep, va, pa, sz, prot); +} +#endif + +static uintptr_t __init best_map_size(uintptr_t load_pa, phys_addr_t size) +{ +#ifdef CONFIG_BOOT_PAGE_ALIGNED + uintptr_t map_sz = PAGE_SIZE; +#else +#ifndef __PAGETABLE_PMD_FOLDED + uintptr_t map_sz = PMD_SIZE; +#else + uintptr_t map_sz = PGDIR_SIZE; +#endif +#endif + +#ifndef __PAGETABLE_PMD_FOLDED + if (!(load_pa & (PMD_SIZE - 1)) && + (size >= PMD_SIZE) && + (map_sz < PMD_SIZE)) + map_sz = PMD_SIZE; +#endif + + if (!(load_pa & (PGDIR_SIZE - 1)) && + (size >= PGDIR_SIZE) && + (map_sz < PGDIR_SIZE)) + map_sz = PGDIR_SIZE; + + return map_sz; +} + /* * The setup_vm() is called from head.S with MMU-off. * @@ -192,46 +385,110 @@ void __set_fixmap(enum fixed_addresses idx, phys_addr_t phys, pgprot_t prot) * Currently, the above requirements are honoured by using custom CFLAGS * for init.o in mm/Makefile. */ -asmlinkage void __init setup_vm(void) +asmlinkage void __init setup_vm(uintptr_t dtb_pa) { - uintptr_t i; - uintptr_t pa = (uintptr_t) &_start; + uintptr_t va, end_va; + uintptr_t load_pa = (uintptr_t)(&_start); + uintptr_t load_sz = (uintptr_t)(&_end) - load_pa; + pgprot_t tableprot = __pgprot(_PAGE_TABLE); pgprot_t prot = __pgprot(pgprot_val(PAGE_KERNEL) | _PAGE_EXEC); + struct mapping_ops ops; - va_pa_offset = PAGE_OFFSET - pa; - pfn_base = PFN_DOWN(pa); + va_pa_offset = PAGE_OFFSET - load_pa; + pfn_base = PFN_DOWN(load_pa); + map_size = best_map_size(load_pa, PGDIR_SIZE); /* Sanity check alignment and size */ BUG_ON((PAGE_OFFSET % PGDIR_SIZE) != 0); - BUG_ON((pa % (PAGE_SIZE * PTRS_PER_PTE)) != 0); + BUG_ON((load_pa % map_size) != 0); + BUG_ON(load_sz > MAX_EARLY_MAPPING_SIZE); + + /* Setup swapper ops */ + ops.get_pte_virt = early_get_pte_virt; + ops.alloc_pte = early_alloc_pte; + ops.get_pmd_virt = NULL; + ops.alloc_pmd = NULL; #ifndef __PAGETABLE_PMD_FOLDED - for (i = 0; i < (-PAGE_OFFSET)/PGDIR_SIZE; ++i) { - size_t o = (PAGE_OFFSET >> PGDIR_SHIFT) % PTRS_PER_PGD + i; + /* Update mapping ops for PMD */ + ops.get_pmd_virt = early_get_pmd_virt; + ops.alloc_pmd = early_alloc_pmd; + + /* Setup swapper PGD and PMD for fixmap */ + create_pgd_mapping(swapper_pg_dir, FIXADDR_START, + (uintptr_t)fixmap_pmd, PGDIR_SIZE, tableprot, &ops); + create_pmd_mapping(fixmap_pmd, FIXADDR_START, + (uintptr_t)fixmap_pte, PMD_SIZE, tableprot, &ops); +#else + /* Setup swapper PGD for fixmap */ + create_pgd_mapping(swapper_pg_dir, FIXADDR_START, + (uintptr_t)fixmap_pte, PGDIR_SIZE, tableprot, &ops); +#endif - 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)); + /* + * Setup swapper PGD covering entire kernel which will allows + * us to reach paging_init(). We map all memory banks later in + * setup_vm_final() below. + */ + end_va = PAGE_OFFSET + load_sz; + for (va = PAGE_OFFSET; va < end_va; va += map_size) + create_pgd_mapping(swapper_pg_dir, va, + load_pa + (va - PAGE_OFFSET), + map_size, prot, &ops); + + /* Create fixed mapping for early FDT parsing */ + end_va = __fix_to_virt(FIX_FDT) + FIX_FDT_SIZE; + for (va = __fix_to_virt(FIX_FDT); va < end_va; va += PAGE_SIZE) + create_pte_mapping(fixmap_pte, va, + dtb_pa + (va - __fix_to_virt(FIX_FDT)), + PAGE_SIZE, prot); +} + +static void __init setup_vm_final(void) +{ + phys_addr_t pa, start, end; + struct memblock_region *reg; + struct mapping_ops ops; + pgprot_t prot = __pgprot(pgprot_val(PAGE_KERNEL) | _PAGE_EXEC); + + /* Setup mapping ops */ + ops.get_pte_virt = final_get_pte_virt; + ops.alloc_pte = final_alloc_pte; +#ifndef __PAGETABLE_PMD_FOLDED + ops.get_pmd_virt = final_get_pmd_virt; + ops.alloc_pmd = final_alloc_pmd; #else - for (i = 0; i < (-PAGE_OFFSET)/PGDIR_SIZE; ++i) { - size_t o = (PAGE_OFFSET >> PGDIR_SHIFT) % PTRS_PER_PGD + i; + ops.get_pmd_virt = NULL; + ops.alloc_pmd = NULL; +#endif - swapper_pg_dir[o] = - pfn_pgd(PFN_DOWN(pa + i * PGDIR_SIZE), prot); + /* Map all memory banks */ + for_each_memblock(memory, reg) { + start = reg->base; + end = start + reg->size; + + if (start >= end) + break; + if (memblock_is_nomap(reg)) + continue; + if (start <= __pa(PAGE_OFFSET) && + __pa(PAGE_OFFSET) < end) + start = __pa(PAGE_OFFSET); + + for (pa = start; pa < end; pa += map_size) + create_pgd_mapping(swapper_pg_dir, + (uintptr_t)__va(pa), pa, + map_size, prot, &ops); } - swapper_pg_dir[(FIXADDR_START >> PGDIR_SHIFT) % PTRS_PER_PGD] = - pfn_pgd(PFN_DOWN((uintptr_t)fixmap_pte), - __pgprot(_PAGE_TABLE)); -#endif + clear_fixmap(FIX_PTE); + clear_fixmap(FIX_PMD); +} + +void __init paging_init(void) +{ + setup_vm_final(); + setup_zero_page(); + local_flush_tlb_all(); + zone_sizes_init(); } -- 2.17.1
