linux-kernel - Re: [PATCH v2] arm64/mm: Refactor {pgd, pud, pmd, pte}

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Date:   Mon, 14 Sep 2020 11:01:48 +0530
From:   Anshuman Khandual <anshuman.khandual@....com>
To:     Gavin Shan <gshan@...hat.com>, linux-arm-kernel@...ts.infradead.org
Cc:     linux-kernel@...r.kernel.org, mark.rutland@....com,
        catalin.marinas@....com, will@...nel.org, shan.gavin@...il.com
Subject: Re: [PATCH v2] arm64/mm: Refactor {pgd, pud, pmd, pte}_ERROR()



On 09/14/2020 05:17 AM, Gavin Shan wrote:
> The function __{pgd, pud, pmd, pte}_error() are introduced so that
> they can be called by {pgd, pud, pmd, pte}_ERROR(). However, some
> of the functions could never be called when the corresponding page
> table level isn't enabled. For example, __{pud, pmd}_error() are
> unused when PUD and PMD are folded to PGD.

Right, it makes sense not to have these helpers generally available.
Given pxx_ERROR() is enabled only when required page table level is
available, with a CONFIG_PGTABLE_LEVEL check.

> 
> This removes __{pgd, pud, pmd, pte}_error() and call pr_err() from
> {pgd, pud, pmd, pte}_ERROR() directly, similar to what x86/powerpc
> are doing. With this, the code looks a bit simplified either.

Do we need p4d_ERROR() here as well !

> 
> Signed-off-by: Gavin Shan <gshan@...hat.com>
> ---
> v2: Fix build warning caused by wrong printk format
> ---
>  arch/arm64/include/asm/pgtable.h | 17 ++++++++---------
>  arch/arm64/kernel/traps.c        | 20 --------------------
>  2 files changed, 8 insertions(+), 29 deletions(-)
> 
> diff --git a/arch/arm64/include/asm/pgtable.h b/arch/arm64/include/asm/pgtable.h
> index d5d3fbe73953..e0ab81923c30 100644
> --- a/arch/arm64/include/asm/pgtable.h
> +++ b/arch/arm64/include/asm/pgtable.h
> @@ -35,11 +35,6 @@
>  
>  extern struct page *vmemmap;
>  
> -extern void __pte_error(const char *file, int line, unsigned long val);
> -extern void __pmd_error(const char *file, int line, unsigned long val);
> -extern void __pud_error(const char *file, int line, unsigned long val);
> -extern void __pgd_error(const char *file, int line, unsigned long val);
> -
>  #ifdef CONFIG_TRANSPARENT_HUGEPAGE
>  #define __HAVE_ARCH_FLUSH_PMD_TLB_RANGE
>  
> @@ -57,7 +52,8 @@ extern void __pgd_error(const char *file, int line, unsigned long val);
>  extern unsigned long empty_zero_page[PAGE_SIZE / sizeof(unsigned long)];
>  #define ZERO_PAGE(vaddr)	phys_to_page(__pa_symbol(empty_zero_page))
>  
> -#define pte_ERROR(pte)		__pte_error(__FILE__, __LINE__, pte_val(pte))
> +#define pte_ERROR(e)	\
> +	pr_err("%s:%d: bad pte %016llx.\n", __FILE__, __LINE__, pte_val(e))
>  
>  /*
>   * Macros to convert between a physical address and its placement in a
> @@ -541,7 +537,8 @@ static inline unsigned long pmd_page_vaddr(pmd_t pmd)
>  
>  #if CONFIG_PGTABLE_LEVELS > 2
>  
> -#define pmd_ERROR(pmd)		__pmd_error(__FILE__, __LINE__, pmd_val(pmd))
> +#define pmd_ERROR(e)	\
> +	pr_err("%s:%d: bad pmd %016llx.\n", __FILE__, __LINE__, pmd_val(e))
>  
>  #define pud_none(pud)		(!pud_val(pud))
>  #define pud_bad(pud)		(!(pud_val(pud) & PUD_TABLE_BIT))
> @@ -608,7 +605,8 @@ static inline unsigned long pud_page_vaddr(pud_t pud)
>  
>  #if CONFIG_PGTABLE_LEVELS > 3
>  
> -#define pud_ERROR(pud)		__pud_error(__FILE__, __LINE__, pud_val(pud))
> +#define pud_ERROR(e)	\
> +	pr_err("%s:%d: bad pud %016llx.\n", __FILE__, __LINE__, pud_val(e))
>  
>  #define p4d_none(p4d)		(!p4d_val(p4d))
>  #define p4d_bad(p4d)		(!(p4d_val(p4d) & 2))
> @@ -667,7 +665,8 @@ static inline unsigned long p4d_page_vaddr(p4d_t p4d)
>  
>  #endif  /* CONFIG_PGTABLE_LEVELS > 3 */
>  
> -#define pgd_ERROR(pgd)		__pgd_error(__FILE__, __LINE__, pgd_val(pgd))
> +#define pgd_ERROR(e)	\
> +	pr_err("%s:%d: bad pgd %016llx.\n", __FILE__, __LINE__, pgd_val(e))

A line break in these macros might not be required any more, as checkpatch.pl
now accepts bit longer lines.

>  
>  #define pgd_set_fixmap(addr)	((pgd_t *)set_fixmap_offset(FIX_PGD, addr))
>  #define pgd_clear_fixmap()	clear_fixmap(FIX_PGD)
> diff --git a/arch/arm64/kernel/traps.c b/arch/arm64/kernel/traps.c
> index 13ebd5ca2070..12fba7136dbd 100644
> --- a/arch/arm64/kernel/traps.c
> +++ b/arch/arm64/kernel/traps.c
> @@ -935,26 +935,6 @@ asmlinkage void enter_from_user_mode(void)
>  }
>  NOKPROBE_SYMBOL(enter_from_user_mode);
>  
> -void __pte_error(const char *file, int line, unsigned long val)
> -{
> -	pr_err("%s:%d: bad pte %016lx.\n", file, line, val);
> -}
> -
> -void __pmd_error(const char *file, int line, unsigned long val)
> -{
> -	pr_err("%s:%d: bad pmd %016lx.\n", file, line, val);
> -}
> -
> -void __pud_error(const char *file, int line, unsigned long val)
> -{
> -	pr_err("%s:%d: bad pud %016lx.\n", file, line, val);
> -}
> -
> -void __pgd_error(const char *file, int line, unsigned long val)
> -{
> -	pr_err("%s:%d: bad pgd %016lx.\n", file, line, val);
> -}

While moving %016lx now becomes %016llx. I guess this should be okay.
Looks much cleaner to have removed these helpers from trap.c

> -
>  /* GENERIC_BUG traps */
>  
>  int is_valid_bugaddr(unsigned long addr)
>