Re: [PATCH v2] arm64/mm: Refactor {pgd, pud, pmd, pte}_ERROR()

[Gavin Shan]

Hi Anshuman,

On 9/14/20 3:31 PM, Anshuman Khandual wrote:
> 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.

Yep.

> > 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 !

p4d_ERROR() is defined in include/asm-generic/pgtable-nop4d.h, which
is always included because we have 4 levels of page tables to the
maximum.

> > Signed-off-by: Gavin Shan <gshan@xxxxxxxxxx>
> > ---
> > 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.

Correct, but I guess it's nice to limit the width to 80 characters :)

> >   
> >   #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

Yep.

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

Thanks,
Gavin