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| Started by | Stefan Agner <stefan@agner.ch> |
|---|---|
| First post | 2015-06-06 14:40 +0200 |
| Last post | 2015-06-06 15:40 +0200 |
| Articles | 3 — 2 participants |
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[PATCH v3] ARM: early fixmap support for earlycon Stefan Agner <stefan@agner.ch> - 2015-06-06 14:40 +0200
Re: [PATCH v3] ARM: early fixmap support for earlycon Russell King - ARM Linux <linux@arm.linux.org.uk> - 2015-06-06 14:50 +0200
Re: [PATCH v3] ARM: early fixmap support for earlycon Stefan Agner <stefan@agner.ch> - 2015-06-06 15:40 +0200
| From | Stefan Agner <stefan@agner.ch> |
|---|---|
| Date | 2015-06-06 14:40 +0200 |
| Subject | [PATCH v3] ARM: early fixmap support for earlycon |
| Message-ID | <pylyh-6q-13@gated-at.bofh.it> |
Add early fixmap support, initially to support permanent, fixed
mapping support for early console. A temporary, early pte is
created which is migrated to a permanent mapping in paging_init.
This is also needed since the attributes may change as the memory
types are initialized. The 3MiB range of fixmap spans two pte
tables, but currently only one pte is created for early fixmap
support.
Re-add FIX_KMAP_BEGIN to the index calculation in highmem.c since
the index for kmap does not start at zero anymore. This reverts
4221e2e6b316 ("ARM: 8031/1: fixmap: remove FIX_KMAP_BEGIN and
FIX_KMAP_END") to some extent.
Cc: Mark Salter <msalter@redhat.com>
Cc: Russell King <linux@arm.linux.org.uk>
Cc: Kees Cook <keescook@chromium.org>
Cc: Laura Abbott <lauraa@codeaurora.org>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Signed-off-by: Rob Herring <robh@kernel.org>
Signed-off-by: Stefan Agner <stefan@agner.ch>
---
Changes since v2:
- Rebased and tested on rmk/for-next
- Flush TLB's when clearing the temporary PMD in early_fixmap_shutdown
Changes since v1 (RFC):
- Rebased and tested on v3.19-rc5
- Spelling errors in comments and commit message
- Added Rob's SOB
arch/arm/Kconfig | 3 ++
arch/arm/include/asm/fixmap.h | 13 +++++++-
arch/arm/kernel/setup.c | 3 ++
arch/arm/mm/highmem.c | 6 ++--
arch/arm/mm/mmu.c | 78 +++++++++++++++++++++++++++++++++++++++++--
5 files changed, 96 insertions(+), 7 deletions(-)
diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
index d0950ce..ef164a7 100644
--- a/arch/arm/Kconfig
+++ b/arch/arm/Kconfig
@@ -186,6 +186,9 @@ config ARCH_HAS_ILOG2_U64
config ARCH_HAS_BANDGAP
bool
+config FIX_EARLYCON_MEM
+ def_bool y
+
config GENERIC_HWEIGHT
bool
default y
diff --git a/arch/arm/include/asm/fixmap.h b/arch/arm/include/asm/fixmap.h
index 0415eae..2d8b12b 100644
--- a/arch/arm/include/asm/fixmap.h
+++ b/arch/arm/include/asm/fixmap.h
@@ -6,9 +6,13 @@
#define FIXADDR_TOP (FIXADDR_END - PAGE_SIZE)
#include <asm/kmap_types.h>
+#include <asm/pgtable.h>
enum fixed_addresses {
- FIX_KMAP_BEGIN,
+ FIX_EARLYCON_MEM_BASE,
+ __end_of_permanent_fixed_addresses,
+
+ FIX_KMAP_BEGIN = __end_of_permanent_fixed_addresses,
FIX_KMAP_END = FIX_KMAP_BEGIN + (KM_TYPE_NR * NR_CPUS) - 1,
/* Support writing RO kernel text via kprobes, jump labels, etc. */
@@ -18,7 +22,14 @@ enum fixed_addresses {
__end_of_fixed_addresses
};
+#define FIXMAP_PAGE_COMMON (L_PTE_YOUNG | L_PTE_PRESENT | L_PTE_XN | L_PTE_DIRTY)
+
+#define FIXMAP_PAGE_NORMAL (FIXMAP_PAGE_COMMON | L_PTE_MT_WRITEBACK)
+#define FIXMAP_PAGE_IO (FIXMAP_PAGE_COMMON | L_PTE_MT_DEV_SHARED | L_PTE_SHARED)
+#define FIXMAP_PAGE_NOCACHE FIXMAP_PAGE_IO
+
void __set_fixmap(enum fixed_addresses idx, phys_addr_t phys, pgprot_t prot);
+void __init early_fixmap_init(void);
#include <asm-generic/fixmap.h>
diff --git a/arch/arm/kernel/setup.c b/arch/arm/kernel/setup.c
index e6d8c76..6f03beb 100644
--- a/arch/arm/kernel/setup.c
+++ b/arch/arm/kernel/setup.c
@@ -37,6 +37,7 @@
#include <asm/cpu.h>
#include <asm/cputype.h>
#include <asm/elf.h>
+#include <asm/fixmap.h>
#include <asm/procinfo.h>
#include <asm/psci.h>
#include <asm/sections.h>
@@ -953,6 +954,8 @@ void __init setup_arch(char **cmdline_p)
strlcpy(cmd_line, boot_command_line, COMMAND_LINE_SIZE);
*cmdline_p = cmd_line;
+ early_fixmap_init();
+
parse_early_param();
#ifdef CONFIG_MMU
diff --git a/arch/arm/mm/highmem.c b/arch/arm/mm/highmem.c
index b98895d..c7097f9 100644
--- a/arch/arm/mm/highmem.c
+++ b/arch/arm/mm/highmem.c
@@ -78,7 +78,7 @@ void *kmap_atomic(struct page *page)
type = kmap_atomic_idx_push();
- idx = type + KM_TYPE_NR * smp_processor_id();
+ idx = FIX_KMAP_BEGIN + type + KM_TYPE_NR * smp_processor_id();
vaddr = __fix_to_virt(idx);
#ifdef CONFIG_DEBUG_HIGHMEM
/*
@@ -105,7 +105,7 @@ void __kunmap_atomic(void *kvaddr)
if (kvaddr >= (void *)FIXADDR_START) {
type = kmap_atomic_idx();
- idx = type + KM_TYPE_NR * smp_processor_id();
+ idx = FIX_KMAP_BEGIN + type + KM_TYPE_NR * smp_processor_id();
if (cache_is_vivt())
__cpuc_flush_dcache_area((void *)vaddr, PAGE_SIZE);
@@ -135,7 +135,7 @@ void *kmap_atomic_pfn(unsigned long pfn)
return page_address(page);
type = kmap_atomic_idx_push();
- idx = type + KM_TYPE_NR * smp_processor_id();
+ idx = FIX_KMAP_BEGIN + type + KM_TYPE_NR * smp_processor_id();
vaddr = __fix_to_virt(idx);
#ifdef CONFIG_DEBUG_HIGHMEM
BUG_ON(!pte_none(get_fixmap_pte(vaddr)));
diff --git a/arch/arm/mm/mmu.c b/arch/arm/mm/mmu.c
index 6ca7d9a..d3e9702 100644
--- a/arch/arm/mm/mmu.c
+++ b/arch/arm/mm/mmu.c
@@ -357,6 +357,47 @@ const struct mem_type *get_mem_type(unsigned int type)
}
EXPORT_SYMBOL(get_mem_type);
+static pte_t *(*pte_offset_fixmap)(pmd_t *dir, unsigned long addr);
+
+static pte_t bm_pte[PTRS_PER_PTE + PTE_HWTABLE_PTRS]
+ __aligned(PTE_HWTABLE_OFF + PTE_HWTABLE_SIZE) __initdata;
+
+static pte_t * __init pte_offset_early_fixmap(pmd_t *dir, unsigned long addr)
+{
+ return &bm_pte[pte_index(addr)];
+}
+
+static pte_t *pte_offset_late_fixmap(pmd_t *dir, unsigned long addr)
+{
+ return pte_offset_kernel(dir, addr);
+}
+
+static inline pmd_t * __init fixmap_pmd(unsigned long addr)
+{
+ pgd_t *pgd = pgd_offset_k(addr);
+ pud_t *pud = pud_offset(pgd, addr);
+ pmd_t *pmd = pmd_offset(pud, addr);
+
+ return pmd;
+}
+
+void __init early_fixmap_init(void)
+{
+ pmd_t *pmd;
+
+ /*
+ * The early fixmap range spans multiple pmds, for which
+ * we are not prepared:
+ */
+ BUILD_BUG_ON((__fix_to_virt(__end_of_permanent_fixed_addresses) >> PMD_SHIFT)
+ != FIXADDR_TOP >> PMD_SHIFT);
+
+ pmd = fixmap_pmd(FIXADDR_TOP);
+ pmd_populate_kernel(&init_mm, pmd, bm_pte);
+
+ pte_offset_fixmap = &pte_offset_early_fixmap;
+}
+
/*
* To avoid TLB flush broadcasts, this uses local_flush_tlb_kernel_range().
* As a result, this can only be called with preemption disabled, as under
@@ -365,7 +406,7 @@ EXPORT_SYMBOL(get_mem_type);
void __set_fixmap(enum fixed_addresses idx, phys_addr_t phys, pgprot_t prot)
{
unsigned long vaddr = __fix_to_virt(idx);
- pte_t *pte = pte_offset_kernel(pmd_off_k(vaddr), vaddr);
+ pte_t *pte = pte_offset_fixmap(pmd_off_k(vaddr), vaddr);
/* Make sure fixmap region does not exceed available allocation. */
BUILD_BUG_ON(FIXADDR_START + (__end_of_fixed_addresses * PAGE_SIZE) >
@@ -855,7 +896,7 @@ static void __init create_mapping(struct map_desc *md)
}
if ((md->type == MT_DEVICE || md->type == MT_ROM) &&
- md->virtual >= PAGE_OFFSET &&
+ 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",
(long long)__pfn_to_phys((u64)md->pfn), md->virtual);
@@ -1231,7 +1272,7 @@ static void __init devicemaps_init(const struct machine_desc *mdesc)
early_trap_init(vectors);
- for (addr = VMALLOC_START; addr; addr += PMD_SIZE)
+ for (addr = VMALLOC_START; addr < FIXADDR_START; addr += PMD_SIZE)
pmd_clear(pmd_off_k(addr));
/*
@@ -1483,6 +1524,36 @@ void __init early_paging_init(const struct machine_desc *mdesc)
#endif
+static void __init early_fixmap_shutdown(void)
+{
+ int i;
+ unsigned long va = fix_to_virt(__end_of_permanent_fixed_addresses - 1);
+
+ pte_offset_fixmap = &pte_offset_late_fixmap;
+ pmd_clear(fixmap_pmd(va));
+ local_flush_tlb_kernel_page(va);
+
+ for (i = 0; i < __end_of_permanent_fixed_addresses; i++) {
+ pte_t *pte;
+ struct map_desc map;
+
+ map.virtual = fix_to_virt(i);
+ pte = pte_offset_early_fixmap(pmd_off_k(map.virtual), map.virtual);
+
+ /* Only i/o device mappings are supported ATM */
+ if (pte_none(*pte) ||
+ (pte_val(*pte) & L_PTE_MT_MASK) != L_PTE_MT_DEV_SHARED)
+ continue;
+
+ map.pfn = pte_pfn(*pte);
+ map.type = MT_DEVICE;
+ map.length = PAGE_SIZE;
+
+ create_mapping(&map);
+ }
+}
+
+
/*
* paging_init() sets up the page tables, initialises the zone memory
* maps, and sets up the zero page, bad page and bad page tables.
@@ -1495,6 +1566,7 @@ void __init paging_init(const struct machine_desc *mdesc)
prepare_page_table();
map_lowmem();
dma_contiguous_remap();
+ early_fixmap_shutdown();
devicemaps_init(mdesc);
kmap_init();
tcm_init();
--
2.4.2
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| From | Russell King - ARM Linux <linux@arm.linux.org.uk> |
|---|---|
| Date | 2015-06-06 14:50 +0200 |
| Message-ID | <pylHX-ie-7@gated-at.bofh.it> |
| In reply to | #1159885 |
On Sat, Jun 06, 2015 at 02:31:28PM +0200, Stefan Agner wrote:
> Add early fixmap support, initially to support permanent, fixed
> mapping support for early console. A temporary, early pte is
> created which is migrated to a permanent mapping in paging_init.
> This is also needed since the attributes may change as the memory
> types are initialized. The 3MiB range of fixmap spans two pte
> tables, but currently only one pte is created for early fixmap
> support.
>
> Re-add FIX_KMAP_BEGIN to the index calculation in highmem.c since
> the index for kmap does not start at zero anymore. This reverts
> 4221e2e6b316 ("ARM: 8031/1: fixmap: remove FIX_KMAP_BEGIN and
> FIX_KMAP_END") to some extent.
>
> Cc: Mark Salter <msalter@redhat.com>
> Cc: Russell King <linux@arm.linux.org.uk>
> Cc: Kees Cook <keescook@chromium.org>
> Cc: Laura Abbott <lauraa@codeaurora.org>
> Cc: Arnd Bergmann <arnd@arndb.de>
> Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>
> Signed-off-by: Rob Herring <robh@kernel.org>
> Signed-off-by: Stefan Agner <stefan@agner.ch>
> ---
> Changes since v2:
> - Rebased and tested on rmk/for-next
> - Flush TLB's when clearing the temporary PMD in early_fixmap_shutdown
>
> Changes since v1 (RFC):
> - Rebased and tested on v3.19-rc5
> - Spelling errors in comments and commit message
> - Added Rob's SOB
>
> arch/arm/Kconfig | 3 ++
> arch/arm/include/asm/fixmap.h | 13 +++++++-
> arch/arm/kernel/setup.c | 3 ++
> arch/arm/mm/highmem.c | 6 ++--
> arch/arm/mm/mmu.c | 78 +++++++++++++++++++++++++++++++++++++++++--
> 5 files changed, 96 insertions(+), 7 deletions(-)
>
> diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
> index d0950ce..ef164a7 100644
> --- a/arch/arm/Kconfig
> +++ b/arch/arm/Kconfig
> @@ -186,6 +186,9 @@ config ARCH_HAS_ILOG2_U64
> config ARCH_HAS_BANDGAP
> bool
>
> +config FIX_EARLYCON_MEM
> + def_bool y
> +
> config GENERIC_HWEIGHT
> bool
> default y
> diff --git a/arch/arm/include/asm/fixmap.h b/arch/arm/include/asm/fixmap.h
> index 0415eae..2d8b12b 100644
> --- a/arch/arm/include/asm/fixmap.h
> +++ b/arch/arm/include/asm/fixmap.h
> @@ -6,9 +6,13 @@
> #define FIXADDR_TOP (FIXADDR_END - PAGE_SIZE)
>
> #include <asm/kmap_types.h>
> +#include <asm/pgtable.h>
>
> enum fixed_addresses {
> - FIX_KMAP_BEGIN,
> + FIX_EARLYCON_MEM_BASE,
> + __end_of_permanent_fixed_addresses,
> +
> + FIX_KMAP_BEGIN = __end_of_permanent_fixed_addresses,
> FIX_KMAP_END = FIX_KMAP_BEGIN + (KM_TYPE_NR * NR_CPUS) - 1,
>
> /* Support writing RO kernel text via kprobes, jump labels, etc. */
> @@ -18,7 +22,14 @@ enum fixed_addresses {
> __end_of_fixed_addresses
> };
>
> +#define FIXMAP_PAGE_COMMON (L_PTE_YOUNG | L_PTE_PRESENT | L_PTE_XN | L_PTE_DIRTY)
> +
> +#define FIXMAP_PAGE_NORMAL (FIXMAP_PAGE_COMMON | L_PTE_MT_WRITEBACK)
> +#define FIXMAP_PAGE_IO (FIXMAP_PAGE_COMMON | L_PTE_MT_DEV_SHARED | L_PTE_SHARED)
> +#define FIXMAP_PAGE_NOCACHE FIXMAP_PAGE_IO
I'm really not happy with this. What are the expected semantics of the
set_fixmap_nocache() and set_fixmap_offset_nocache() ? Are they there
for mapping a device, or are they there for mapping _memory_ ?
I would prefer that FIXMAP_PAGE_NOCACHE is _not_ provided until the
semantics of that can be clarified, as there is a difference between the
two on ARM.
> +
> void __set_fixmap(enum fixed_addresses idx, phys_addr_t phys, pgprot_t prot);
> +void __init early_fixmap_init(void);
>
> #include <asm-generic/fixmap.h>
>
> diff --git a/arch/arm/kernel/setup.c b/arch/arm/kernel/setup.c
> index e6d8c76..6f03beb 100644
> --- a/arch/arm/kernel/setup.c
> +++ b/arch/arm/kernel/setup.c
> @@ -37,6 +37,7 @@
> #include <asm/cpu.h>
> #include <asm/cputype.h>
> #include <asm/elf.h>
> +#include <asm/fixmap.h>
> #include <asm/procinfo.h>
> #include <asm/psci.h>
> #include <asm/sections.h>
> @@ -953,6 +954,8 @@ void __init setup_arch(char **cmdline_p)
> strlcpy(cmd_line, boot_command_line, COMMAND_LINE_SIZE);
> *cmdline_p = cmd_line;
>
> + early_fixmap_init();
> +
> parse_early_param();
>
> #ifdef CONFIG_MMU
> diff --git a/arch/arm/mm/highmem.c b/arch/arm/mm/highmem.c
> index b98895d..c7097f9 100644
> --- a/arch/arm/mm/highmem.c
> +++ b/arch/arm/mm/highmem.c
> @@ -78,7 +78,7 @@ void *kmap_atomic(struct page *page)
>
> type = kmap_atomic_idx_push();
>
> - idx = type + KM_TYPE_NR * smp_processor_id();
> + idx = FIX_KMAP_BEGIN + type + KM_TYPE_NR * smp_processor_id();
> vaddr = __fix_to_virt(idx);
> #ifdef CONFIG_DEBUG_HIGHMEM
> /*
> @@ -105,7 +105,7 @@ void __kunmap_atomic(void *kvaddr)
>
> if (kvaddr >= (void *)FIXADDR_START) {
> type = kmap_atomic_idx();
> - idx = type + KM_TYPE_NR * smp_processor_id();
> + idx = FIX_KMAP_BEGIN + type + KM_TYPE_NR * smp_processor_id();
>
> if (cache_is_vivt())
> __cpuc_flush_dcache_area((void *)vaddr, PAGE_SIZE);
> @@ -135,7 +135,7 @@ void *kmap_atomic_pfn(unsigned long pfn)
> return page_address(page);
>
> type = kmap_atomic_idx_push();
> - idx = type + KM_TYPE_NR * smp_processor_id();
> + idx = FIX_KMAP_BEGIN + type + KM_TYPE_NR * smp_processor_id();
> vaddr = __fix_to_virt(idx);
> #ifdef CONFIG_DEBUG_HIGHMEM
> BUG_ON(!pte_none(get_fixmap_pte(vaddr)));
> diff --git a/arch/arm/mm/mmu.c b/arch/arm/mm/mmu.c
> index 6ca7d9a..d3e9702 100644
> --- a/arch/arm/mm/mmu.c
> +++ b/arch/arm/mm/mmu.c
> @@ -357,6 +357,47 @@ const struct mem_type *get_mem_type(unsigned int type)
> }
> EXPORT_SYMBOL(get_mem_type);
>
> +static pte_t *(*pte_offset_fixmap)(pmd_t *dir, unsigned long addr);
> +
> +static pte_t bm_pte[PTRS_PER_PTE + PTE_HWTABLE_PTRS]
> + __aligned(PTE_HWTABLE_OFF + PTE_HWTABLE_SIZE) __initdata;
> +
> +static pte_t * __init pte_offset_early_fixmap(pmd_t *dir, unsigned long addr)
> +{
> + return &bm_pte[pte_index(addr)];
> +}
> +
> +static pte_t *pte_offset_late_fixmap(pmd_t *dir, unsigned long addr)
> +{
> + return pte_offset_kernel(dir, addr);
> +}
> +
> +static inline pmd_t * __init fixmap_pmd(unsigned long addr)
> +{
> + pgd_t *pgd = pgd_offset_k(addr);
> + pud_t *pud = pud_offset(pgd, addr);
> + pmd_t *pmd = pmd_offset(pud, addr);
> +
> + return pmd;
> +}
> +
> +void __init early_fixmap_init(void)
> +{
> + pmd_t *pmd;
> +
> + /*
> + * The early fixmap range spans multiple pmds, for which
> + * we are not prepared:
> + */
> + BUILD_BUG_ON((__fix_to_virt(__end_of_permanent_fixed_addresses) >> PMD_SHIFT)
> + != FIXADDR_TOP >> PMD_SHIFT);
> +
> + pmd = fixmap_pmd(FIXADDR_TOP);
> + pmd_populate_kernel(&init_mm, pmd, bm_pte);
> +
> + pte_offset_fixmap = &pte_offset_early_fixmap;
Please don't use "address-of function" in the kernel, it's really not
necessary and is just plain confusing. We don't use it elsewhere, so
there's no reason to be different.
> +}
> +
> /*
> * To avoid TLB flush broadcasts, this uses local_flush_tlb_kernel_range().
> * As a result, this can only be called with preemption disabled, as under
> @@ -365,7 +406,7 @@ EXPORT_SYMBOL(get_mem_type);
> void __set_fixmap(enum fixed_addresses idx, phys_addr_t phys, pgprot_t prot)
> {
> unsigned long vaddr = __fix_to_virt(idx);
> - pte_t *pte = pte_offset_kernel(pmd_off_k(vaddr), vaddr);
> + pte_t *pte = pte_offset_fixmap(pmd_off_k(vaddr), vaddr);
>
> /* Make sure fixmap region does not exceed available allocation. */
> BUILD_BUG_ON(FIXADDR_START + (__end_of_fixed_addresses * PAGE_SIZE) >
> @@ -855,7 +896,7 @@ static void __init create_mapping(struct map_desc *md)
> }
>
> if ((md->type == MT_DEVICE || md->type == MT_ROM) &&
> - md->virtual >= PAGE_OFFSET &&
> + 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",
> (long long)__pfn_to_phys((u64)md->pfn), md->virtual);
> @@ -1231,7 +1272,7 @@ static void __init devicemaps_init(const struct machine_desc *mdesc)
>
> early_trap_init(vectors);
>
> - for (addr = VMALLOC_START; addr; addr += PMD_SIZE)
> + for (addr = VMALLOC_START; addr < FIXADDR_START; addr += PMD_SIZE)
> pmd_clear(pmd_off_k(addr));
You introduce a bug here - we no logner clear the very top entry of the
page tables, which means it could contain anything - and means that the
subsequent creation of the L2 table in early_pte_alloc() can fail.
>
> /*
> @@ -1483,6 +1524,36 @@ void __init early_paging_init(const struct machine_desc *mdesc)
>
> #endif
>
> +static void __init early_fixmap_shutdown(void)
> +{
> + int i;
> + unsigned long va = fix_to_virt(__end_of_permanent_fixed_addresses - 1);
> +
> + pte_offset_fixmap = &pte_offset_late_fixmap;
Again, please don't use "address-of function".
> + pmd_clear(fixmap_pmd(va));
> + local_flush_tlb_kernel_page(va);
> +
> + for (i = 0; i < __end_of_permanent_fixed_addresses; i++) {
> + pte_t *pte;
> + struct map_desc map;
> +
> + map.virtual = fix_to_virt(i);
> + pte = pte_offset_early_fixmap(pmd_off_k(map.virtual), map.virtual);
> +
> + /* Only i/o device mappings are supported ATM */
> + if (pte_none(*pte) ||
> + (pte_val(*pte) & L_PTE_MT_MASK) != L_PTE_MT_DEV_SHARED)
> + continue;
> +
> + map.pfn = pte_pfn(*pte);
> + map.type = MT_DEVICE;
> + map.length = PAGE_SIZE;
> +
> + create_mapping(&map);
> + }
> +}
> +
> +
> /*
> * paging_init() sets up the page tables, initialises the zone memory
> * maps, and sets up the zero page, bad page and bad page tables.
> @@ -1495,6 +1566,7 @@ void __init paging_init(const struct machine_desc *mdesc)
> prepare_page_table();
> map_lowmem();
> dma_contiguous_remap();
> + early_fixmap_shutdown();
> devicemaps_init(mdesc);
> kmap_init();
> tcm_init();
> --
> 2.4.2
>
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| From | Stefan Agner <stefan@agner.ch> |
|---|---|
| Date | 2015-06-06 15:40 +0200 |
| Message-ID | <pymum-1tT-27@gated-at.bofh.it> |
| In reply to | #1159887 |
On 2015-06-06 14:48, Russell King - ARM Linux wrote:
> On Sat, Jun 06, 2015 at 02:31:28PM +0200, Stefan Agner wrote:
<snip>
>> --- a/arch/arm/include/asm/fixmap.h
>> +++ b/arch/arm/include/asm/fixmap.h
>> @@ -6,9 +6,13 @@
>> #define FIXADDR_TOP (FIXADDR_END - PAGE_SIZE)
>>
>> #include <asm/kmap_types.h>
>> +#include <asm/pgtable.h>
>>
>> enum fixed_addresses {
>> - FIX_KMAP_BEGIN,
>> + FIX_EARLYCON_MEM_BASE,
>> + __end_of_permanent_fixed_addresses,
>> +
>> + FIX_KMAP_BEGIN = __end_of_permanent_fixed_addresses,
>> FIX_KMAP_END = FIX_KMAP_BEGIN + (KM_TYPE_NR * NR_CPUS) - 1,
>>
>> /* Support writing RO kernel text via kprobes, jump labels, etc. */
>> @@ -18,7 +22,14 @@ enum fixed_addresses {
>> __end_of_fixed_addresses
>> };
>>
>> +#define FIXMAP_PAGE_COMMON (L_PTE_YOUNG | L_PTE_PRESENT | L_PTE_XN | L_PTE_DIRTY)
>> +
>> +#define FIXMAP_PAGE_NORMAL (FIXMAP_PAGE_COMMON | L_PTE_MT_WRITEBACK)
>> +#define FIXMAP_PAGE_IO (FIXMAP_PAGE_COMMON | L_PTE_MT_DEV_SHARED | L_PTE_SHARED)
>> +#define FIXMAP_PAGE_NOCACHE FIXMAP_PAGE_IO
>
> I'm really not happy with this. What are the expected semantics of the
> set_fixmap_nocache() and set_fixmap_offset_nocache() ? Are they there
> for mapping a device, or are they there for mapping _memory_ ?
>
> I would prefer that FIXMAP_PAGE_NOCACHE is _not_ provided until the
> semantics of that can be clarified, as there is a difference between the
> two on ARM.
set_fixmap_nocache is used for PCIe and IO APIC stuff, so actually IO
devices. However, as far as I understand the x86 page table definitions
in pgtable_types.h, IO devices are not explicitly uncached on x86. The
define set_fixmap_nocache make sure IO devices are mapped uncached...
Maybe set_fixmap_io_nocache instead of set_fixmap_nocache would be more
appropriate...?
Maybe the initial authors of the common fixmap.h have a more clear
understanding of the expected semantics, Mark?
Since the focus currently is on set_fixmap_io, we could define
FIXMAP_PAGE_IO only for the time being...?
Agreed to the rest, will apply the review in v4.
--
Stefan
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