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Message-ID: <0808610c-ba23-8b95-dd85-81b78fffe2fb@ghiti.fr>
Date: Fri, 12 Jun 2020 08:30:20 -0400
From: Alex Ghiti <alex@...ti.fr>
To: Atish Patra <atishp@...shpatra.org>
Cc: Michael Ellerman <mpe@...erman.id.au>,
Benjamin Herrenschmidt <benh@...nel.crashing.org>,
Paul Mackerras <paulus@...ba.org>,
Paul Walmsley <paul.walmsley@...ive.com>,
Palmer Dabbelt <palmer@...belt.com>,
Albert Ou <aou@...s.berkeley.edu>,
Anup Patel <Anup.Patel@....com>,
Atish Patra <Atish.Patra@....com>,
Zong Li <zong.li@...ive.com>,
"linux-kernel@...r.kernel.org List" <linux-kernel@...r.kernel.org>,
linuxppc-dev@...ts.ozlabs.org,
linux-riscv <linux-riscv@...ts.infradead.org>
Subject: Re: [PATCH v5 1/4] riscv: Move kernel mapping to vmalloc zone
Hi Atish,
Le 6/11/20 à 5:34 PM, Atish Patra a écrit :
> On Sun, Jun 7, 2020 at 1:01 AM Alexandre Ghiti <alex@...ti.fr> wrote:
>> This is a preparatory patch for relocatable kernel.
>>
>> The kernel used to be linked at PAGE_OFFSET address and used to be loaded
>> physically at the beginning of the main memory. Therefore, we could use
>> the linear mapping for the kernel mapping.
>>
>> But the relocated kernel base address will be different from PAGE_OFFSET
>> and since in the linear mapping, two different virtual addresses cannot
>> point to the same physical address, the kernel mapping needs to lie outside
>> the linear mapping.
>>
>> In addition, because modules and BPF must be close to the kernel (inside
>> +-2GB window), the kernel is placed at the end of the vmalloc zone minus
>> 2GB, which leaves room for modules and BPF. The kernel could not be
>> placed at the beginning of the vmalloc zone since other vmalloc
>> allocations from the kernel could get all the +-2GB window around the
>> kernel which would prevent new modules and BPF programs to be loaded.
>>
>> Signed-off-by: Alexandre Ghiti <alex@...ti.fr>
>> Reviewed-by: Zong Li <zong.li@...ive.com>
>> ---
>> arch/riscv/boot/loader.lds.S | 3 +-
>> arch/riscv/include/asm/page.h | 10 +++++-
>> arch/riscv/include/asm/pgtable.h | 38 ++++++++++++++-------
>> arch/riscv/kernel/head.S | 3 +-
>> arch/riscv/kernel/module.c | 4 +--
>> arch/riscv/kernel/vmlinux.lds.S | 3 +-
>> arch/riscv/mm/init.c | 58 +++++++++++++++++++++++++-------
>> arch/riscv/mm/physaddr.c | 2 +-
>> 8 files changed, 88 insertions(+), 33 deletions(-)
>>
>> diff --git a/arch/riscv/boot/loader.lds.S b/arch/riscv/boot/loader.lds.S
>> index 47a5003c2e28..62d94696a19c 100644
>> --- a/arch/riscv/boot/loader.lds.S
>> +++ b/arch/riscv/boot/loader.lds.S
>> @@ -1,13 +1,14 @@
>> /* SPDX-License-Identifier: GPL-2.0 */
>>
>> #include <asm/page.h>
>> +#include <asm/pgtable.h>
>>
>> OUTPUT_ARCH(riscv)
>> ENTRY(_start)
>>
>> SECTIONS
>> {
>> - . = PAGE_OFFSET;
>> + . = KERNEL_LINK_ADDR;
>>
>> .payload : {
>> *(.payload)
>> diff --git a/arch/riscv/include/asm/page.h b/arch/riscv/include/asm/page.h
>> index 2d50f76efe48..48bb09b6a9b7 100644
>> --- a/arch/riscv/include/asm/page.h
>> +++ b/arch/riscv/include/asm/page.h
>> @@ -90,18 +90,26 @@ typedef struct page *pgtable_t;
>>
>> #ifdef CONFIG_MMU
>> extern unsigned long va_pa_offset;
>> +extern unsigned long va_kernel_pa_offset;
>> extern unsigned long pfn_base;
>> #define ARCH_PFN_OFFSET (pfn_base)
>> #else
>> #define va_pa_offset 0
>> +#define va_kernel_pa_offset 0
>> #define ARCH_PFN_OFFSET (PAGE_OFFSET >> PAGE_SHIFT)
>> #endif /* CONFIG_MMU */
>>
>> extern unsigned long max_low_pfn;
>> extern unsigned long min_low_pfn;
>> +extern unsigned long kernel_virt_addr;
>>
>> #define __pa_to_va_nodebug(x) ((void *)((unsigned long) (x) + va_pa_offset))
>> -#define __va_to_pa_nodebug(x) ((unsigned long)(x) - va_pa_offset)
>> +#define linear_mapping_va_to_pa(x) ((unsigned long)(x) - va_pa_offset)
>> +#define kernel_mapping_va_to_pa(x) \
>> + ((unsigned long)(x) - va_kernel_pa_offset)
>> +#define __va_to_pa_nodebug(x) \
>> + (((x) >= PAGE_OFFSET) ? \
>> + linear_mapping_va_to_pa(x) : kernel_mapping_va_to_pa(x))
>>
>> #ifdef CONFIG_DEBUG_VIRTUAL
>> extern phys_addr_t __virt_to_phys(unsigned long x);
>> diff --git a/arch/riscv/include/asm/pgtable.h b/arch/riscv/include/asm/pgtable.h
>> index 35b60035b6b0..94ef3b49dfb6 100644
>> --- a/arch/riscv/include/asm/pgtable.h
>> +++ b/arch/riscv/include/asm/pgtable.h
>> @@ -11,23 +11,29 @@
>>
>> #include <asm/pgtable-bits.h>
>>
>> -#ifndef __ASSEMBLY__
>> -
>> -/* Page Upper Directory not used in RISC-V */
>> -#include <asm-generic/pgtable-nopud.h>
>> -#include <asm/page.h>
>> -#include <asm/tlbflush.h>
>> -#include <linux/mm_types.h>
>> -
>> -#ifdef CONFIG_MMU
>> +#ifndef CONFIG_MMU
>> +#define KERNEL_VIRT_ADDR PAGE_OFFSET
>> +#define KERNEL_LINK_ADDR PAGE_OFFSET
>> +#else
>> +/*
>> + * Leave 2GB for modules and BPF that must lie within a 2GB range around
>> + * the kernel.
>> + */
>> +#define KERNEL_VIRT_ADDR (VMALLOC_END - SZ_2G + 1)
>> +#define KERNEL_LINK_ADDR KERNEL_VIRT_ADDR
>>
>> #define VMALLOC_SIZE (KERN_VIRT_SIZE >> 1)
>> #define VMALLOC_END (PAGE_OFFSET - 1)
>> #define VMALLOC_START (PAGE_OFFSET - VMALLOC_SIZE)
>>
>> #define BPF_JIT_REGION_SIZE (SZ_128M)
>> -#define BPF_JIT_REGION_START (PAGE_OFFSET - BPF_JIT_REGION_SIZE)
>> -#define BPF_JIT_REGION_END (VMALLOC_END)
>> +#define BPF_JIT_REGION_START PFN_ALIGN((unsigned long)&_end)
>> +#define BPF_JIT_REGION_END (BPF_JIT_REGION_START + BPF_JIT_REGION_SIZE)
>> +
> As these mappings have changed a few times in recent months including
> this one, I think it would be
> better to have virtual memory layout documentation in RISC-V similar
> to other architectures.
>
> If you can include the page table layout for 3/4 level page tables in
> the same document, that would be really helpful.
>
Yes, I'll do that in a separate commit.
Thanks,
Alex
>> +#ifdef CONFIG_64BIT
>> +#define VMALLOC_MODULE_START BPF_JIT_REGION_END
>> +#define VMALLOC_MODULE_END (((unsigned long)&_start & PAGE_MASK) + SZ_2G)
>> +#endif
>>
>> /*
>> * Roughly size the vmemmap space to be large enough to fit enough
>> @@ -57,9 +63,16 @@
>> #define FIXADDR_SIZE PGDIR_SIZE
>> #endif
>> #define FIXADDR_START (FIXADDR_TOP - FIXADDR_SIZE)
>> -
>> #endif
>>
>> +#ifndef __ASSEMBLY__
>> +
>> +/* Page Upper Directory not used in RISC-V */
>> +#include <asm-generic/pgtable-nopud.h>
>> +#include <asm/page.h>
>> +#include <asm/tlbflush.h>
>> +#include <linux/mm_types.h>
>> +
>> #ifdef CONFIG_64BIT
>> #include <asm/pgtable-64.h>
>> #else
>> @@ -483,6 +496,7 @@ static inline void __kernel_map_pages(struct page *page, int numpages, int enabl
>>
>> #define kern_addr_valid(addr) (1) /* FIXME */
>>
>> +extern char _start[];
>> extern void *dtb_early_va;
>> void setup_bootmem(void);
>> void paging_init(void);
>> diff --git a/arch/riscv/kernel/head.S b/arch/riscv/kernel/head.S
>> index 98a406474e7d..8f5bb7731327 100644
>> --- a/arch/riscv/kernel/head.S
>> +++ b/arch/riscv/kernel/head.S
>> @@ -49,7 +49,8 @@ ENTRY(_start)
>> #ifdef CONFIG_MMU
>> relocate:
>> /* Relocate return address */
>> - li a1, PAGE_OFFSET
>> + la a1, kernel_virt_addr
>> + REG_L a1, 0(a1)
>> la a2, _start
>> sub a1, a1, a2
>> add ra, ra, a1
>> diff --git a/arch/riscv/kernel/module.c b/arch/riscv/kernel/module.c
>> index 8bbe5dbe1341..1a8fbe05accf 100644
>> --- a/arch/riscv/kernel/module.c
>> +++ b/arch/riscv/kernel/module.c
>> @@ -392,12 +392,10 @@ int apply_relocate_add(Elf_Shdr *sechdrs, const char *strtab,
>> }
>>
>> #if defined(CONFIG_MMU) && defined(CONFIG_64BIT)
>> -#define VMALLOC_MODULE_START \
>> - max(PFN_ALIGN((unsigned long)&_end - SZ_2G), VMALLOC_START)
>> void *module_alloc(unsigned long size)
>> {
>> return __vmalloc_node_range(size, 1, VMALLOC_MODULE_START,
>> - VMALLOC_END, GFP_KERNEL,
>> + VMALLOC_MODULE_END, GFP_KERNEL,
>> PAGE_KERNEL_EXEC, 0, NUMA_NO_NODE,
>> __builtin_return_address(0));
>> }
>> diff --git a/arch/riscv/kernel/vmlinux.lds.S b/arch/riscv/kernel/vmlinux.lds.S
>> index 0339b6bbe11a..a9abde62909f 100644
>> --- a/arch/riscv/kernel/vmlinux.lds.S
>> +++ b/arch/riscv/kernel/vmlinux.lds.S
>> @@ -4,7 +4,8 @@
>> * Copyright (C) 2017 SiFive
>> */
>>
>> -#define LOAD_OFFSET PAGE_OFFSET
>> +#include <asm/pgtable.h>
>> +#define LOAD_OFFSET KERNEL_LINK_ADDR
>> #include <asm/vmlinux.lds.h>
>> #include <asm/page.h>
>> #include <asm/cache.h>
>> diff --git a/arch/riscv/mm/init.c b/arch/riscv/mm/init.c
>> index 736de6c8739f..71da78914645 100644
>> --- a/arch/riscv/mm/init.c
>> +++ b/arch/riscv/mm/init.c
>> @@ -22,6 +22,9 @@
>>
>> #include "../kernel/head.h"
>>
>> +unsigned long kernel_virt_addr = KERNEL_VIRT_ADDR;
>> +EXPORT_SYMBOL(kernel_virt_addr);
>> +
>> unsigned long empty_zero_page[PAGE_SIZE / sizeof(unsigned long)]
>> __page_aligned_bss;
>> EXPORT_SYMBOL(empty_zero_page);
>> @@ -178,8 +181,12 @@ void __init setup_bootmem(void)
>> }
>>
>> #ifdef CONFIG_MMU
>> +/* Offset between linear mapping virtual address and kernel load address */
>> unsigned long va_pa_offset;
>> EXPORT_SYMBOL(va_pa_offset);
>> +/* Offset between kernel mapping virtual address and kernel load address */
>> +unsigned long va_kernel_pa_offset;
>> +EXPORT_SYMBOL(va_kernel_pa_offset);
>> unsigned long pfn_base;
>> EXPORT_SYMBOL(pfn_base);
>>
>> @@ -271,7 +278,7 @@ static phys_addr_t __init alloc_pmd(uintptr_t va)
>> if (mmu_enabled)
>> return memblock_phys_alloc(PAGE_SIZE, PAGE_SIZE);
>>
>> - pmd_num = (va - PAGE_OFFSET) >> PGDIR_SHIFT;
>> + pmd_num = (va - kernel_virt_addr) >> PGDIR_SHIFT;
>> BUG_ON(pmd_num >= NUM_EARLY_PMDS);
>> return (uintptr_t)&early_pmd[pmd_num * PTRS_PER_PMD];
>> }
>> @@ -372,14 +379,30 @@ static uintptr_t __init best_map_size(phys_addr_t base, phys_addr_t size)
>> #error "setup_vm() is called from head.S before relocate so it should not use absolute addressing."
>> #endif
>>
>> +static uintptr_t load_pa, load_sz;
>> +
>> +static void __init create_kernel_page_table(pgd_t *pgdir, uintptr_t map_size)
>> +{
>> + uintptr_t va, end_va;
>> +
>> + end_va = kernel_virt_addr + load_sz;
>> + for (va = kernel_virt_addr; va < end_va; va += map_size)
>> + create_pgd_mapping(pgdir, va,
>> + load_pa + (va - kernel_virt_addr),
>> + map_size, PAGE_KERNEL_EXEC);
>> +}
>> +
>> asmlinkage void __init setup_vm(uintptr_t dtb_pa)
>> {
>> uintptr_t va, end_va;
>> - uintptr_t load_pa = (uintptr_t)(&_start);
>> - uintptr_t load_sz = (uintptr_t)(&_end) - load_pa;
>> uintptr_t map_size = best_map_size(load_pa, MAX_EARLY_MAPPING_SIZE);
>>
>> + load_pa = (uintptr_t)(&_start);
>> + load_sz = (uintptr_t)(&_end) - load_pa;
>> +
>> va_pa_offset = PAGE_OFFSET - load_pa;
>> + va_kernel_pa_offset = kernel_virt_addr - load_pa;
>> +
>> pfn_base = PFN_DOWN(load_pa);
>>
>> /*
>> @@ -402,26 +425,22 @@ asmlinkage void __init setup_vm(uintptr_t dtb_pa)
>> 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, PAGE_OFFSET,
>> + create_pgd_mapping(trampoline_pg_dir, kernel_virt_addr,
>> (uintptr_t)trampoline_pmd, PGDIR_SIZE, PAGE_TABLE);
>> - create_pmd_mapping(trampoline_pmd, PAGE_OFFSET,
>> + create_pmd_mapping(trampoline_pmd, kernel_virt_addr,
>> load_pa, PMD_SIZE, PAGE_KERNEL_EXEC);
>> #else
>> /* Setup trampoline PGD */
>> - create_pgd_mapping(trampoline_pg_dir, PAGE_OFFSET,
>> + create_pgd_mapping(trampoline_pg_dir, kernel_virt_addr,
>> load_pa, PGDIR_SIZE, PAGE_KERNEL_EXEC);
>> #endif
>>
>> /*
>> - * Setup early PGD covering entire kernel which will allows
>> + * 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.
>> */
>> - end_va = PAGE_OFFSET + load_sz;
>> - for (va = PAGE_OFFSET; va < end_va; va += map_size)
>> - create_pgd_mapping(early_pg_dir, va,
>> - load_pa + (va - PAGE_OFFSET),
>> - map_size, PAGE_KERNEL_EXEC);
>> + create_kernel_page_table(early_pg_dir, map_size);
>>
>> /* Create fixed mapping for early FDT parsing */
>> end_va = __fix_to_virt(FIX_FDT) + FIX_FDT_SIZE;
>> @@ -441,6 +460,7 @@ static void __init setup_vm_final(void)
>> uintptr_t va, map_size;
>> phys_addr_t pa, start, end;
>> struct memblock_region *reg;
>> + static struct vm_struct vm_kernel = { 0 };
>>
>> /* Set mmu_enabled flag */
>> mmu_enabled = true;
>> @@ -467,10 +487,22 @@ static void __init setup_vm_final(void)
>> for (pa = start; pa < end; pa += map_size) {
>> va = (uintptr_t)__va(pa);
>> create_pgd_mapping(swapper_pg_dir, va, pa,
>> - map_size, PAGE_KERNEL_EXEC);
>> + map_size, PAGE_KERNEL);
>> }
>> }
>>
>> + /* Map the kernel */
>> + create_kernel_page_table(swapper_pg_dir, PMD_SIZE);
>> +
>> + /* Reserve the vmalloc area occupied by the kernel */
>> + vm_kernel.addr = (void *)kernel_virt_addr;
>> + vm_kernel.phys_addr = load_pa;
>> + vm_kernel.size = (load_sz + PMD_SIZE - 1) & ~(PMD_SIZE - 1);
>> + vm_kernel.flags = VM_MAP | VM_NO_GUARD;
>> + vm_kernel.caller = __builtin_return_address(0);
>> +
>> + vm_area_add_early(&vm_kernel);
>> +
>> /* Clear fixmap PTE and PMD mappings */
>> clear_fixmap(FIX_PTE);
>> clear_fixmap(FIX_PMD);
>> diff --git a/arch/riscv/mm/physaddr.c b/arch/riscv/mm/physaddr.c
>> index e8e4dcd39fed..35703d5ef5fd 100644
>> --- a/arch/riscv/mm/physaddr.c
>> +++ b/arch/riscv/mm/physaddr.c
>> @@ -23,7 +23,7 @@ EXPORT_SYMBOL(__virt_to_phys);
>>
>> phys_addr_t __phys_addr_symbol(unsigned long x)
>> {
>> - unsigned long kernel_start = (unsigned long)PAGE_OFFSET;
>> + unsigned long kernel_start = (unsigned long)kernel_virt_addr;
>> unsigned long kernel_end = (unsigned long)_end;
>>
>> /*
>> --
>> 2.20.1
>>
>>
>
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