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Message-ID: <alpine.LFD.2.11.1404131305120.980@knanqh.ubzr>
Date: Sun, 13 Apr 2014 13:34:51 -0400 (EDT)
From: Nicolas Pitre <nicolas.pitre@...aro.org>
To: Liu hua <sdu.liu@...wei.com>
cc: Russell King - ARM Linux <linux@....linux.org.uk>,
Will Deacon <will.deacon@....com>,
linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
wangnan0@...wei.com, peifeiyue@...wei.com, liusdu@....com,
m.szyprowski@...sung.com
Subject: Re: [PATCH v2 2/2] ARM : change fixmap mapping region to support 32
CPUs
On Sun, 13 Apr 2014, Liu hua wrote:
> Hi Nicolas.
>
> Sure, your suggestion made my patch looks better. How about that :
>
> Thanks,
> Liu Hua
There is something else that bothers me.
> -------------------------------------------------
>
> Changes from v2:
> moved new codes to highmem.c as more as possible.
> unchanged Document/arm/memory.txt.
>
>
> 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
>
> Acked-by: Nicolas Pitre <nico@...aro.org>
> Signed-off-by: Liu Hua <sdu.liu@...wei.com>
> ---
> arch/arm/include/asm/fixmap.h | 4 ++--
> arch/arm/include/asm/highmem.h | 1 +
> arch/arm/mm/highmem.c | 28 ++++++++++++++++++++++------
> arch/arm/mm/mmu.c | 4 ++++
> 4 files changed, 29 insertions(+), 8 deletions(-)
>
> diff --git a/arch/arm/include/asm/fixmap.h b/arch/arm/include/asm/fixmap.h
> index bbae919..014a70d 100644
> --- a/arch/arm/include/asm/fixmap.h
> +++ b/arch/arm/include/asm/fixmap.h
> @@ -13,8 +13,8 @@
> * 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)
>
> #define FIX_KMAP_BEGIN 0
> 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 21b9e1b..fa97896 100644
> --- a/arch/arm/mm/highmem.c
> +++ b/arch/arm/mm/highmem.c
> @@ -18,6 +18,22 @@
> #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(FIX_KMAP_BEGIN + 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);
> + idx -= FIX_KMAP_BEGIN;
> + return *(fixmap_page_table + idx);
FIX_KMAP_BEGIN represents the starting point for mapping fixmap indices
to page table entries. So here you should _add_ the
FIX_KMAP_BEGIN offset to the page table index not substract it.
Currently FIX_KMAP_BEGIN is defined to 0 but still.
> +}
> +
> void *kmap(struct page *page)
> {
> might_sleep();
> @@ -69,14 +85,14 @@ 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)));
This is therefore also wrong. It should be
fixmap_page_table + idx + FIX_KMAP_BEGIN.
> #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 +111,7 @@ void __kunmap_atomic(void *kvaddr)
> __cpuc_flush_dcache_area((void *)vaddr, PAGE_SIZE);
> #ifdef CONFIG_DEBUG_HIGHMEM
> BUG_ON(vaddr != __fix_to_virt(FIX_KMAP_BEGIN + idx));
> - set_top_pte(vaddr, __pte(0));
> + set_fixmap_pte(idx, __pte(0));
> #else
> (void) idx; /* to kill a warning */
> #endif
> @@ -119,9 +135,9 @@ void *kmap_atomic_pfn(unsigned long pfn)
> idx = type + KM_TYPE_NR * smp_processor_id();
> vaddr = __fix_to_virt(FIX_KMAP_BEGIN + idx);
> #ifdef CONFIG_DEBUG_HIGHMEM
> - BUG_ON(!pte_none(get_top_pte(vaddr)));
> + BUG_ON(!pte_none(*(fixmap_page_table + idx)));
Ditto here.
In fact, this FIX_KMAP_BEGIN is only creating more confusing code for
nothing as we define it to 0 anyway, and it is not used by non
architecture specific code. So I'd suggest you create a patch to be
applied before this one that simply gets rid of FIX_KMAP_BEGIN and
FIX_KMAP_END altogether. We could reintroduce them back if ever they're
needed.
Nicolas
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