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ARM: 9012/1: move device tree mapping out of linear region

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commit 7a1be318f5795cb66fa0dc86b3ace427fe68057f upstream

On ARM, setting up the linear region is tricky, given the constraints
around placement and alignment of the memblocks, and how the kernel
itself as well as the DT are placed in physical memory.

Let's simplify matters a bit, by moving the device tree mapping to the
top of the address space, right between the end of the vmalloc region
and the start of the the fixmap region, and create a read-only mapping
for it that is independent of the size of the linear region, and how it
is organized.

Since this region was formerly used as a guard region, which will now be
populated fully on LPAE builds by this read-only mapping (which will
still be able to function as a guard region for stray writes), bump the
start of the [underutilized] fixmap region by 512 KB as well, to ensure
that there is always a proper guard region here. Doing so still leaves
ample room for the fixmap space, even with NR_CPUS set to its maximum
value of 32.

Tested-by: Linus Walleij <linus.walleij@linaro.org>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Reviewed-by: Nicolas Pitre <nico@fluxnic.net>
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Signed-off-by: Russell King <rmk+kernel@armlinux.org.uk>
Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Ard Biesheuvel 2021-05-10 06:21:09 -07:00 committed by Greg Kroah-Hartman
parent 6cdbafc2ad
commit 1eb7756902
8 changed files with 38 additions and 17 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

7
Documentation/arm/memory.rst
View File

@ -45,9 +45,14 @@ fffe8000 fffeffff DTCM mapping area for platforms with
fffe0000 fffe7fff ITCM mapping area for platforms with
ITCM mounted inside the CPU.
ffc00000 ffefffff Fixmap mapping region. Addresses provided
ffc80000 ffefffff Fixmap mapping region. Addresses provided
by fix_to_virt() will be located here.
ffc00000 ffc7ffff Guard region
ff800000 ffbfffff Permanent, fixed read-only mapping of the
firmware provided DT blob
fee00000 feffffff Mapping of PCI I/O space. This is a static
mapping within the vmalloc space.

2
arch/arm/include/asm/fixmap.h
View File

@ -2,7 +2,7 @@
#ifndef _ASM_FIXMAP_H
#define _ASM_FIXMAP_H
#define FIXADDR_START 0xffc00000UL
#define FIXADDR_START 0xffc80000UL
#define FIXADDR_END 0xfff00000UL
#define FIXADDR_TOP (FIXADDR_END - PAGE_SIZE)

5
arch/arm/include/asm/memory.h
View File

@ -67,6 +67,10 @@
*/
#define XIP_VIRT_ADDR(physaddr) (MODULES_VADDR + ((physaddr) & 0x000fffff))
#define FDT_FIXED_BASE UL(0xff800000)
#define FDT_FIXED_SIZE (2 * PMD_SIZE)
#define FDT_VIRT_ADDR(physaddr) ((void *)(FDT_FIXED_BASE | (physaddr) % PMD_SIZE))
#if !defined(CONFIG_SMP) && !defined(CONFIG_ARM_LPAE)
/*
* Allow 16MB-aligned ioremap pages
@ -107,6 +111,7 @@ extern unsigned long vectors_base;
#define MODULES_VADDR PAGE_OFFSET
#define XIP_VIRT_ADDR(physaddr) (physaddr)
#define FDT_VIRT_ADDR(physaddr) ((void *)(physaddr))
#endif /* !CONFIG_MMU */

5
arch/arm/kernel/head.S
View File

@ -275,9 +275,8 @@ __create_page_tables:
*/
mov r0, r2, lsr #SECTION_SHIFT
movs r0, r0, lsl #SECTION_SHIFT
subne r3, r0, r8
addne r3, r3, #PAGE_OFFSET
addne r3, r4, r3, lsr #(SECTION_SHIFT - PMD_ORDER)
ldrne r3, =FDT_FIXED_BASE >> (SECTION_SHIFT - PMD_ORDER)
addne r3, r3, r4
orrne r6, r7, r0
strne r6, [r3], #1 << PMD_ORDER
addne r6, r6, #1 << SECTION_SHIFT

11
arch/arm/kernel/setup.c
View File

@ -18,6 +18,7 @@
#include <linux/of_platform.h>
#include <linux/init.h>
#include <linux/kexec.h>
#include <linux/libfdt.h>
#include <linux/of_fdt.h>
#include <linux/cpu.h>
#include <linux/interrupt.h>
@ -89,7 +90,6 @@ unsigned int cacheid __read_mostly;
EXPORT_SYMBOL(cacheid);
unsigned int __atags_pointer __initdata;
void *atags_vaddr __initdata;
unsigned int system_rev;
EXPORT_SYMBOL(system_rev);
@ -1083,13 +1083,18 @@ void __init hyp_mode_check(void)
void __init setup_arch(char **cmdline_p)
{
const struct machine_desc *mdesc = NULL;
void *atags_vaddr = NULL;
if (__atags_pointer)
atags_vaddr = phys_to_virt(__atags_pointer);
atags_vaddr = FDT_VIRT_ADDR(__atags_pointer);
setup_processor();
if (atags_vaddr)
if (atags_vaddr) {
mdesc = setup_machine_fdt(atags_vaddr);
if (mdesc)
memblock_reserve(__atags_pointer,
fdt_totalsize(atags_vaddr));
}
if (!mdesc)
mdesc = setup_machine_tags(atags_vaddr, __machine_arch_type);
if (!mdesc) {

1
arch/arm/mm/init.c
View File

@ -223,7 +223,6 @@ void __init arm_memblock_init(const struct machine_desc *mdesc)
if (mdesc->reserve)
mdesc->reserve();
early_init_fdt_reserve_self();
early_init_fdt_scan_reserved_mem();
/* reserve memory for DMA contiguous allocations */

20
arch/arm/mm/mmu.c
View File

@ -39,6 +39,8 @@
#include "mm.h"
#include "tcm.h"
extern unsigned long __atags_pointer;
/*
* empty_zero_page is a special page that is used for
* zero-initialized data and COW.
@ -946,7 +948,7 @@ static void __init create_mapping(struct map_desc *md)
return;
}
if ((md->type == MT_DEVICE || md->type == MT_ROM) &&
if (md->type == MT_DEVICE &&
md->virtual >= PAGE_OFFSET && md->virtual < FIXADDR_START &&
(md->virtual < VMALLOC_START || md->virtual >= VMALLOC_END)) {
pr_warn("BUG: mapping for 0x%08llx at 0x%08lx out of vmalloc space\n",
@ -1333,6 +1335,15 @@ static void __init devicemaps_init(const struct machine_desc *mdesc)
for (addr = VMALLOC_START; addr < (FIXADDR_TOP & PMD_MASK); addr += PMD_SIZE)
pmd_clear(pmd_off_k(addr));
if (__atags_pointer) {
/* create a read-only mapping of the device tree */
map.pfn = __phys_to_pfn(__atags_pointer & SECTION_MASK);
map.virtual = FDT_FIXED_BASE;
map.length = FDT_FIXED_SIZE;
map.type = MT_ROM;
create_mapping(&map);
}
/*
* Map the kernel if it is XIP.
* It is always first in the modulearea.
@ -1489,8 +1500,7 @@ static void __init map_lowmem(void)
}
#ifdef CONFIG_ARM_PV_FIXUP
extern void *atags_vaddr;
typedef void pgtables_remap(long long offset, unsigned long pgd, void *bdata);
typedef void pgtables_remap(long long offset, unsigned long pgd);
pgtables_remap lpae_pgtables_remap_asm;
/*
@ -1503,7 +1513,6 @@ static void __init early_paging_init(const struct machine_desc *mdesc)
unsigned long pa_pgd;
unsigned int cr, ttbcr;
long long offset;
void *boot_data;
if (!mdesc->pv_fixup)
return;
@ -1520,7 +1529,6 @@ static void __init early_paging_init(const struct machine_desc *mdesc)
*/
lpae_pgtables_remap = (pgtables_remap *)(unsigned long)__pa(lpae_pgtables_remap_asm);
pa_pgd = __pa(swapper_pg_dir);
boot_data = atags_vaddr;
barrier();
pr_info("Switching physical address space to 0x%08llx\n",
@ -1556,7 +1564,7 @@ static void __init early_paging_init(const struct machine_desc *mdesc)
* needs to be assembly. It's fairly simple, as we're using the
* temporary tables setup by the initial assembly code.
*/
lpae_pgtables_remap(offset, pa_pgd, boot_data);
lpae_pgtables_remap(offset, pa_pgd);
/* Re-enable the caches and cacheable TLB walks */
asm volatile("mcr p15, 0, %0, c2, c0, 2" : : "r" (ttbcr));

4
arch/arm/mm/pv-fixup-asm.S
View File

@ -39,8 +39,8 @@ ENTRY(lpae_pgtables_remap_asm)
/* Update level 2 entries for the boot data */
add r7, r2, #0x1000
add r7, r7, r3, lsr #SECTION_SHIFT - L2_ORDER
bic r7, r7, #(1 << L2_ORDER) - 1
movw r3, #FDT_FIXED_BASE >> (SECTION_SHIFT - L2_ORDER)
add r7, r7, r3
ldrd r4, r5, [r7]
adds r4, r4, r0
adc r5, r5, r1