Re: [PATCH v2 2/2] ARM : change fixmap mapping region to support 32 CPUs

From: Nicolas Pitre
Date: Mon Apr 14 2014 - 09:50:29 EST

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On Mon, 14 Apr 2014, Liu hua wrote:

> Yes, it seems that FIX_KMAP_BEGIN and FIX_KMAP_END are not as important for
> ARM than that for other architectures (MIPS PowerPC x86), whose FIX_KMAP_BEGIN
> is not 0. I will reminder this in my patch. Anyone who need them can get
> imformantion there.
>
>
> Now the new patchs are following. Maybe I sould resend the patch series
> with a new tag. If It is time to do that. Can I add this information
> "Reviewed-by: Nicolas Pitre <nico@xxxxxxxxxx>" ?
>
> Thanks,
> Liu Hua.
>
> -----------------patch 1-------------------------
>
> Subject: [PATCH 1/2] ARM : fixmap : remove FIX_KMAP_BEGIN and FIX_KMAP_END
>
> It seems that these two variables are not used by non
> architecture specific code. And on ARM FIX_KMAP_BEGIN
> equals zero; FIX_KMAP_END is totally not used by the
> kernel.
>
> This patch removes these two variables. The code will
> become clear when I introduce a bugfix on fixmap mapping

s/clear/clearer/

> region.
>
> Signed-off-by: Liu Hua <sdu.liu@xxxxxxxxxx>
> ---
> arch/arm/include/asm/fixmap.h | 12 ++++++++----
> arch/arm/mm/highmem.c | 6 +++---
> 2 files changed, 11 insertions(+), 7 deletions(-)
>
> diff --git a/arch/arm/include/asm/fixmap.h b/arch/arm/include/asm/fixmap.h
> index bbae919..8675bb9 100644
> --- a/arch/arm/include/asm/fixmap.h
> +++ b/arch/arm/include/asm/fixmap.h
> @@ -17,9 +17,13 @@
> #define FIXADDR_TOP 0xfffe0000UL
> #define FIXADDR_SIZE (FIXADDR_TOP - FIXADDR_START)
>
> -#define FIX_KMAP_BEGIN 0
> -#define FIX_KMAP_END (FIXADDR_SIZE >> PAGE_SHIFT)
> -
> +/* Notice : FIX_KMAP_END and FIX_KMAP_BEGIN are removed.
> + *
> + * Instead, using FIX_KMAP_NR_PTES to tell the pte number
> + * belonged to fixmap mapping region.
> + *
> + */

Please move this comment to the commit log instead. This is not
important enough to occupy that much space in the code.

> +#define FIX_KMAP_NR_PTES (FIXADDR_SIZE >> PAGE_SHIFT)
> #define __fix_to_virt(x) (FIXADDR_START + ((x) << PAGE_SHIFT))
> #define __virt_to_fix(x) (((x) - FIXADDR_START) >> PAGE_SHIFT)
>
> @@ -27,7 +31,7 @@ extern void __this_fixmap_does_not_exist(void);
>
> static inline unsigned long fix_to_virt(const unsigned int idx)
> {
> - if (idx >= FIX_KMAP_END)
> + if (idx >= FIX_KMAP_NR_PTES)
> __this_fixmap_does_not_exist();
> return __fix_to_virt(idx);
> }
> diff --git a/arch/arm/mm/highmem.c b/arch/arm/mm/highmem.c
> index 21b9e1b..e05e8ad 100644
> --- a/arch/arm/mm/highmem.c
> +++ b/arch/arm/mm/highmem.c
> @@ -63,7 +63,7 @@ void *kmap_atomic(struct page *page)
> type = kmap_atomic_idx_push();
>
> idx = type + KM_TYPE_NR * smp_processor_id();
> - vaddr = __fix_to_virt(FIX_KMAP_BEGIN + idx);
> + vaddr = __fix_to_virt(idx);
> #ifdef CONFIG_DEBUG_HIGHMEM
> /*
> * With debugging enabled, kunmap_atomic forces that entry to 0.
> @@ -94,7 +94,7 @@ void __kunmap_atomic(void *kvaddr)
> if (cache_is_vivt())
> __cpuc_flush_dcache_area((void *)vaddr, PAGE_SIZE);
> #ifdef CONFIG_DEBUG_HIGHMEM
> - BUG_ON(vaddr != __fix_to_virt(FIX_KMAP_BEGIN + idx));
> + BUG_ON(vaddr != __fix_to_virt(idx));
> set_top_pte(vaddr, __pte(0));
> #else
> (void) idx; /* to kill a warning */
> @@ -117,7 +117,7 @@ void *kmap_atomic_pfn(unsigned long pfn)
>
> type = kmap_atomic_idx_push();
> idx = type + KM_TYPE_NR * smp_processor_id();
> - vaddr = __fix_to_virt(FIX_KMAP_BEGIN + idx);
> + vaddr = __fix_to_virt(idx);
> #ifdef CONFIG_DEBUG_HIGHMEM
> BUG_ON(!pte_none(get_top_pte(vaddr)));
> #endif
> --
> 1.9.0

With the above details fixed you may add:

Reviewed-by: Nicolas Pitre <nico@xxxxxxxxxx>

> -----------------patch 2-------------------------
>
>
>
> Subject: [PATCH 2/2] ARM : change fixmap mapping region to support 32 CPUs
>
> In 32-bit ARM systems, the fixmap mapping region can support
> no more than 14 CPUs(total: 896k; one CPU: 64K). And we can
> configure NR_CPUS up to 32. So there is a mismatch.
>
> This patch moves fixmapping region downwards to region
> 0xffc00000-0xffe00000 . Then the fixmap mapping region can
> support up to 32 CPUs
>
> Signed-off-by: Liu Hua <sdu.liu@xxxxxxxxxx>
> ---
> Documentation/arm/memory.txt | 2 +-
> arch/arm/include/asm/fixmap.h | 16 ++--------------
> arch/arm/include/asm/highmem.h | 1 +
> arch/arm/mm/highmem.c | 27 +++++++++++++++++++++------
> arch/arm/mm/mmu.c | 4 ++++
> 5 files changed, 29 insertions(+), 21 deletions(-)
>
> diff --git a/Documentation/arm/memory.txt b/Documentation/arm/memory.txt
> index d74e8a5..256c5e0 100644
> --- a/Documentation/arm/memory.txt
> +++ b/Documentation/arm/memory.txt
> @@ -41,7 +41,7 @@ fffe8000 fffeffff DTCM mapping area for platforms with
> fffe0000 fffe7fff ITCM mapping area for platforms with
> ITCM mounted inside the CPU.
>
> -fff00000 fffdffff Fixmap mapping region. Addresses provided
> +fffc0000 ffdfffff Fixmap mapping region. Addresses provided
> by fix_to_virt() will be located here.
>
> fee00000 feffffff Mapping of PCI I/O space. This is a static
> diff --git a/arch/arm/include/asm/fixmap.h b/arch/arm/include/asm/fixmap.h
> index 8675bb9..fb8a5a7 100644
> --- a/arch/arm/include/asm/fixmap.h
> +++ b/arch/arm/include/asm/fixmap.h
> @@ -1,20 +1,8 @@
> #ifndef _ASM_FIXMAP_H
> #define _ASM_FIXMAP_H
>
> -/*
> - * Nothing too fancy for now.
> - *
> - * On ARM we already have well known fixed virtual addresses imposed by
> - * the architecture such as the vector page which is located at 0xffff0000,
> - * therefore a second level page table is already allocated covering
> - * 0xfff00000 upwards.
> - *
> - * The cache flushing code in proc-xscale.S uses the virtual area between
> - * 0xfffe0000 and 0xfffeffff.
> - */
> -
> -#define FIXADDR_START 0xfff00000UL
> -#define FIXADDR_TOP 0xfffe0000UL
> +#define FIXADDR_START 0xffc00000UL
> +#define FIXADDR_TOP 0xffe00000UL
> #define FIXADDR_SIZE (FIXADDR_TOP - FIXADDR_START)
>
> /* Notice : FIX_KMAP_END and FIX_KMAP_BEGIN are removed.
> diff --git a/arch/arm/include/asm/highmem.h b/arch/arm/include/asm/highmem.h
> index 91b99ab..5355795 100644
> --- a/arch/arm/include/asm/highmem.h
> +++ b/arch/arm/include/asm/highmem.h
> @@ -18,6 +18,7 @@
> } while (0)
>
> extern pte_t *pkmap_page_table;
> +extern pte_t *fixmap_page_table;
>
> extern void *kmap_high(struct page *page);
> extern void kunmap_high(struct page *page);
> diff --git a/arch/arm/mm/highmem.c b/arch/arm/mm/highmem.c
> index e05e8ad..45aeaac 100644
> --- a/arch/arm/mm/highmem.c
> +++ b/arch/arm/mm/highmem.c
> @@ -18,6 +18,21 @@
> #include <asm/tlbflush.h>
> #include "mm.h"
>
> +pte_t *fixmap_page_table;
> +
> +static inline void set_fixmap_pte(int idx, pte_t pte)
> +{
> + unsigned long vaddr = __fix_to_virt(idx);
> + set_pte_ext(fixmap_page_table + idx, pte, 0);
> + local_flush_tlb_kernel_page(vaddr);
> +}
> +
> +static inline pte_t get_fixmap_pte(unsigned long vaddr)
> +{
> + unsigned long idx = __virt_to_fix(vaddr);
> + return *(fixmap_page_table + idx);
> +}
> +
> void *kmap(struct page *page)
> {
> might_sleep();
> @@ -69,14 +84,14 @@ void *kmap_atomic(struct page *page)
> * With debugging enabled, kunmap_atomic forces that entry to 0.
> * Make sure it was indeed properly unmapped.
> */
> - BUG_ON(!pte_none(get_top_pte(vaddr)));
> + BUG_ON(!pte_none(*(fixmap_page_table + idx)));
> #endif
> /*
> * When debugging is off, kunmap_atomic leaves the previous mapping
> * in place, so the contained TLB flush ensures the TLB is updated
> * with the new mapping.
> */
> - set_top_pte(vaddr, mk_pte(page, kmap_prot));
> + set_fixmap_pte(idx, mk_pte(page, kmap_prot));
>
> return (void *)vaddr;
> }
> @@ -95,7 +110,7 @@ void __kunmap_atomic(void *kvaddr)
> __cpuc_flush_dcache_area((void *)vaddr, PAGE_SIZE);
> #ifdef CONFIG_DEBUG_HIGHMEM
> BUG_ON(vaddr != __fix_to_virt(idx));
> - set_top_pte(vaddr, __pte(0));
> + set_fixmap_pte(idx, __pte(0));
> #else
> (void) idx; /* to kill a warning */
> #endif
> @@ -119,9 +134,9 @@ void *kmap_atomic_pfn(unsigned long pfn)
> idx = type + KM_TYPE_NR * smp_processor_id();
> vaddr = __fix_to_virt(idx);
> #ifdef CONFIG_DEBUG_HIGHMEM
> - BUG_ON(!pte_none(get_top_pte(vaddr)));
> + BUG_ON(!pte_none(*(fixmap_page_table + idx)));
> #endif
> - set_top_pte(vaddr, pfn_pte(pfn, kmap_prot));
> + set_fixmap_pte(idx, pfn_pte(pfn, kmap_prot));
>
> return (void *)vaddr;
> }
> @@ -133,5 +148,5 @@ struct page *kmap_atomic_to_page(const void *ptr)
> if (vaddr < FIXADDR_START)
> return virt_to_page(ptr);
>
> - return pte_page(get_top_pte(vaddr));
> + return pte_page(get_fixmap_pte(vaddr));
> }
> diff --git a/arch/arm/mm/mmu.c b/arch/arm/mm/mmu.c
> index b68c6b2..09c0a16 100644
> --- a/arch/arm/mm/mmu.c
> +++ b/arch/arm/mm/mmu.c
> @@ -35,6 +35,7 @@
> #include <asm/mach/arch.h>
> #include <asm/mach/map.h>
> #include <asm/mach/pci.h>
> +#include <asm/fixmap.h>
>
> #include "mm.h"
> #include "tcm.h"
> @@ -1359,6 +1360,9 @@ static void __init kmap_init(void)
> #ifdef CONFIG_HIGHMEM
> pkmap_page_table = early_pte_alloc(pmd_off_k(PKMAP_BASE),
> PKMAP_BASE, _PAGE_KERNEL_TABLE);
> +
> + fixmap_page_table = early_pte_alloc(pmd_off_k(FIXADDR_START),
> + FIXADDR_START, _PAGE_KERNEL_TABLE);
> #endif
> }
>
> --
> 1.9.0

Reviewed-by: Nicolas Pitre <nico@xxxxxxxxxx>

>
>
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Next message: Steven Rostedt: "Re: [PATCH] kthreads: kill CLONE_KERNEL, change kernel_thread(kernel_init) to avoid CLONE_SIGHAND"
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In reply to: Liu hua: "Re: [PATCH v2 2/2] ARM : change fixmap mapping region to support 32 CPUs"
Next in thread: Liu hua: "Re: [PATCH v2 2/2] ARM : change fixmap mapping region to support 32 CPUs"
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