linux-kernel - Re: [PATCH] mips: define pud_index() regardless of page table folding

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Message-ID: <191a4b86-3921-e72c-998d-c490de3ee6e0@amsat.org>
Date:   Wed, 15 Apr 2020 08:43:18 +0200
From:   Philippe Mathieu-Daudé <f4bug@...at.org>
To:     Mike Rapoport <rppt@...nel.org>,
        Thomas Bogendoerfer <tsbogend@...ha.franken.de>
Cc:     Paolo Bonzini <pbonzini@...hat.com>, Peter Xu <peterx@...hat.com>,
        maobibo <maobibo@...ngson.cn>,
        Sergei Shtylyov <sergei.shtylyov@...entembedded.com>,
        linux-mips@...r.kernel.org, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org, Mike Rapoport <rppt@...ux.ibm.com>
Subject: Re: [PATCH] mips: define pud_index() regardless of page table folding

On 4/2/20 10:16 AM, Mike Rapoport wrote:
> From: Mike Rapoport <rppt@...ux.ibm.com>
> 
> Commit 31168f033e37 ("mips: drop __pXd_offset() macros that duplicate
> pXd_index() ones") is correct that pud_index() & __pud_offset() are the
> same when pud_index() is actually provided, however it does not take into
> account the __PAGETABLE_PUD_FOLDED case. This has broken MIPS KVM
> compilation because it relied on availability of pud_index().
> 
> Define pud_index() regardless of page table folded. It will evaluate to
> actual index for 4-level pagetables and to 0 for folded PUD level.
> 
> Link: https://lore.kernel.org/lkml/20200331154749.5457-1-pbonzini@redhat.com
> Reported-by: Paolo Bonzini <pbonzini@...hat.com>
> Signed-off-by: Mike Rapoport <rppt@...ux.ibm.com>

Reviewed-by: Philippe Mathieu-Daudé <f4bug@...at.org>

> ---
>  arch/mips/include/asm/pgtable-64.h | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/arch/mips/include/asm/pgtable-64.h b/arch/mips/include/asm/pgtable-64.h
> index f92716cfa4f4..ee5dc0c145b9 100644
> --- a/arch/mips/include/asm/pgtable-64.h
> +++ b/arch/mips/include/asm/pgtable-64.h
> @@ -172,6 +172,8 @@
>  
>  extern pte_t invalid_pte_table[PTRS_PER_PTE];
>  
> +#define pud_index(address)	(((address) >> PUD_SHIFT) & (PTRS_PER_PUD - 1))
> +
>  #ifndef __PAGETABLE_PUD_FOLDED
>  /*
>   * For 4-level pagetables we defines these ourselves, for 3-level the
> @@ -210,8 +212,6 @@ static inline void p4d_clear(p4d_t *p4dp)
>  	p4d_val(*p4dp) = (unsigned long)invalid_pud_table;
>  }
>  
> -#define pud_index(address)	(((address) >> PUD_SHIFT) & (PTRS_PER_PUD - 1))
> -
>  static inline unsigned long p4d_page_vaddr(p4d_t p4d)
>  {
>  	return p4d_val(p4d);
>