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

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>

diff --git a/Documentation/arm/memory.rst b/Documentation/arm/memory.rst
index 0521b4ce5c961d5d67d7354a000e652848015e3d..34bb23c44a710170303c9143670e36551964fc3b 100644 (file)
--- a/Documentation/arm/memory.rst
+++ b/Documentation/arm/memory.rst
@@ -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.
 

diff --git a/arch/arm/include/asm/fixmap.h b/arch/arm/include/asm/fixmap.h
index fc56fc3e19316d423155be0e40632b3282656da6..9575b404019c963a834dd71ba7a2076f847560ca 100644 (file)
--- a/arch/arm/include/asm/fixmap.h
+++ b/arch/arm/include/asm/fixmap.h
@@ -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)
 

diff --git a/arch/arm/include/asm/memory.h b/arch/arm/include/asm/memory.h
index 99035b5891ef44273832b6b722bb6bf4ca6c737f..bb79e52aeb9048e2b51815322b9464d0a529b050 100644 (file)
--- a/arch/arm/include/asm/memory.h
+++ b/arch/arm/include/asm/memory.h
@@ -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 */
 

diff --git a/arch/arm/kernel/head.S b/arch/arm/kernel/head.S
index f8904227e7fdc44dbb170af6fa4c09f17b3d7247..9b18d8c661295920b61bf050d80721283ede7a30 100644 (file)
--- a/arch/arm/kernel/head.S
+++ b/arch/arm/kernel/head.S
@@ -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

diff --git a/arch/arm/kernel/setup.c b/arch/arm/kernel/setup.c
index 306bcd9844be75c362c872e917f848180ce74ab4..694aa6b4bd03d04b1f86b68ca341cc1e28c460aa 100644 (file)
--- a/arch/arm/kernel/setup.c
+++ b/arch/arm/kernel/setup.c
@@ -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) {

diff --git a/arch/arm/mm/init.c b/arch/arm/mm/init.c
index d57112a276f5ac79da2100970e8ca8c6a78af54a..a391804c7ce3c09927e715109107407fae9fb3b1 100644 (file)
--- a/arch/arm/mm/init.c
+++ b/arch/arm/mm/init.c
@@ -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 */

diff --git a/arch/arm/mm/mmu.c b/arch/arm/mm/mmu.c
index 55991fe60054e6767c100f074fb66b3a029475a8..fa259825310c5aced95ac256171d907e3c0f3549 100644 (file)
--- a/arch/arm/mm/mmu.c
+++ b/arch/arm/mm/mmu.c
@@ -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));

diff --git a/arch/arm/mm/pv-fixup-asm.S b/arch/arm/mm/pv-fixup-asm.S
index 8eade04167399ce701dbe761e1dc2acef9f76379..5c5e1952000ab49aeeb03fecafe9a5e032ee0935 100644 (file)
--- a/arch/arm/mm/pv-fixup-asm.S
+++ b/arch/arm/mm/pv-fixup-asm.S
@@ -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