Re: [Xen-devel] [PATCH v2 5/5] x86/mm: only a single instance of gw_page_flags[] is needed

[George Dunlap <george.dunlap@xxxxxxxxxx>]

On 26/10/15 11:53, Jan Beulich wrote:
> None of its elements depends on GUEST_PAGING_LEVELS.
> 
> Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
> Reviewed-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
> ---
> v2: Re-base on top of earlier changes.

Acked-by: George Dunlap <george.dunlap@xxxxxxxxxx>

> 
> --- a/xen/arch/x86/mm/guest_walk.c
> +++ b/xen/arch/x86/mm/guest_walk.c
> @@ -32,30 +32,32 @@ asm(".file \"" __OBJECT_FILE__ "\"");
>  #include <asm/page.h>
>  #include <asm/guest_pt.h>
>  
> +extern const uint32_t gw_page_flags[];
> +#if GUEST_PAGING_LEVELS == CONFIG_PAGING_LEVELS
> +const uint32_t gw_page_flags[] = {
> +    /* I/F -  Usr Wr */
> +    /* 0   0   0   0 */ _PAGE_PRESENT,
> +    /* 0   0   0   1 */ _PAGE_PRESENT|_PAGE_RW,
> +    /* 0   0   1   0 */ _PAGE_PRESENT|_PAGE_USER,
> +    /* 0   0   1   1 */ _PAGE_PRESENT|_PAGE_RW|_PAGE_USER,
> +    /* 0   1   0   0 */ _PAGE_PRESENT,
> +    /* 0   1   0   1 */ _PAGE_PRESENT|_PAGE_RW,
> +    /* 0   1   1   0 */ _PAGE_PRESENT|_PAGE_USER,
> +    /* 0   1   1   1 */ _PAGE_PRESENT|_PAGE_RW|_PAGE_USER,
> +    /* 1   0   0   0 */ _PAGE_PRESENT|_PAGE_NX_BIT,
> +    /* 1   0   0   1 */ _PAGE_PRESENT|_PAGE_RW|_PAGE_NX_BIT,
> +    /* 1   0   1   0 */ _PAGE_PRESENT|_PAGE_USER|_PAGE_NX_BIT,
> +    /* 1   0   1   1 */ _PAGE_PRESENT|_PAGE_RW|_PAGE_USER|_PAGE_NX_BIT,
> +    /* 1   1   0   0 */ _PAGE_PRESENT|_PAGE_NX_BIT,
> +    /* 1   1   0   1 */ _PAGE_PRESENT|_PAGE_RW|_PAGE_NX_BIT,
> +    /* 1   1   1   0 */ _PAGE_PRESENT|_PAGE_USER|_PAGE_NX_BIT,
> +    /* 1   1   1   1 */ _PAGE_PRESENT|_PAGE_RW|_PAGE_USER|_PAGE_NX_BIT,
> +};
> +#endif
>  
>  /* Flags that are needed in a pagetable entry, with the sense of NX inverted 
> */
>  static uint32_t mandatory_flags(struct vcpu *v, uint32_t pfec) 
>  {
> -    static const uint32_t flags[] = {
> -        /* I/F -  Usr Wr */
> -        /* 0   0   0   0 */ _PAGE_PRESENT, 
> -        /* 0   0   0   1 */ _PAGE_PRESENT|_PAGE_RW,
> -        /* 0   0   1   0 */ _PAGE_PRESENT|_PAGE_USER,
> -        /* 0   0   1   1 */ _PAGE_PRESENT|_PAGE_RW|_PAGE_USER,
> -        /* 0   1   0   0 */ _PAGE_PRESENT, 
> -        /* 0   1   0   1 */ _PAGE_PRESENT|_PAGE_RW,
> -        /* 0   1   1   0 */ _PAGE_PRESENT|_PAGE_USER,
> -        /* 0   1   1   1 */ _PAGE_PRESENT|_PAGE_RW|_PAGE_USER,
> -        /* 1   0   0   0 */ _PAGE_PRESENT|_PAGE_NX_BIT, 
> -        /* 1   0   0   1 */ _PAGE_PRESENT|_PAGE_RW|_PAGE_NX_BIT,
> -        /* 1   0   1   0 */ _PAGE_PRESENT|_PAGE_USER|_PAGE_NX_BIT,
> -        /* 1   0   1   1 */ _PAGE_PRESENT|_PAGE_RW|_PAGE_USER|_PAGE_NX_BIT,
> -        /* 1   1   0   0 */ _PAGE_PRESENT|_PAGE_NX_BIT, 
> -        /* 1   1   0   1 */ _PAGE_PRESENT|_PAGE_RW|_PAGE_NX_BIT,
> -        /* 1   1   1   0 */ _PAGE_PRESENT|_PAGE_USER|_PAGE_NX_BIT,
> -        /* 1   1   1   1 */ _PAGE_PRESENT|_PAGE_RW|_PAGE_USER|_PAGE_NX_BIT,
> -    };
> -
>      /* Don't demand not-NX if the CPU wouldn't enforce it. */
>      if ( !guest_supports_nx(v) )
>          pfec &= ~PFEC_insn_fetch;
> @@ -65,7 +67,7 @@ static uint32_t mandatory_flags(struct v
>           && !(pfec & PFEC_user_mode) )
>          pfec &= ~PFEC_write_access;
>  
> -    return flags[(pfec & 0x1f) >> 1] | _PAGE_INVALID_BITS;
> +    return gw_page_flags[(pfec & 0x1f) >> 1] | _PAGE_INVALID_BITS;
>  }
>  
>  /* Modify a guest pagetable entry to set the Accessed and Dirty bits.
> 
> 
> 


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