Re: [Xen-devel] [PATCH v2] xen: arm: Support <32MB frametables

["Chris (Christopher) Brand" <chris.brand@xxxxxxxxxxxx>]

Any thoughts on v2 ?

Chris

> -----Original Message-----
> From: Chris (Christopher) Brand
> Sent: Friday, 07 August, 2015 1:41 PM
> To: 'Julien Grall'; xen-devel@xxxxxxxxxxxxx
> Cc: Stefano Stabellini; Ian Campbell (ian.campbell@xxxxxxxxxx)
> Subject: [PATCH v2] xen: arm: Support <32MB frametables
> 
> setup_frametable_mappings() rounds frametable_size up to a multiple of
> 32MB. This is wasteful on systems with less than 4GB of RAM, although it
> does allow the "contig" bit to be set in the PTEs.
> 
> Where the frametable is less than 32MB in size, instead round up to a
> multiple of 2MB, not setting the "contig" bit in the PTEs.
> 
> Signed-off-by: Chris Brand <chris.brand@xxxxxxxxxxxx>
> ---
> Changed in v2: merged create_32mb_mappings() and
> create_2mb_mappings() into create_mappings(). A side-effect is to fix the
> bug in v1 for
> ARM64 systems with <4GB RAM.
> 
>  xen/arch/arm/mm.c | 37 ++++++++++++++++++++++---------------
>  1 file changed, 22 insertions(+), 15 deletions(-)
> 
> diff --git a/xen/arch/arm/mm.c b/xen/arch/arm/mm.c index
> ae0f34c3c480..fd64fbfdfb93 100644
> --- a/xen/arch/arm/mm.c
> +++ b/xen/arch/arm/mm.c
> @@ -628,25 +628,31 @@ void __cpuinit mmu_init_secondary_cpu(void)  }
> 
>  /* Create Xen's mappings of memory.
> - * Base and virt must be 32MB aligned and size a multiple of 32MB.
> + * Mapping_size must be either 2MB or 32MB.
> + * Base and virt must be mapping_size aligned.
> + * Size must be a multiple of mapping_size.
>   * second must be a contiguous set of second level page tables
>   * covering the region starting at virt_offset. */ -static void __init
> create_32mb_mappings(lpae_t *second,
> -                                        unsigned long virt_offset,
> -                                        unsigned long base_mfn,
> -                                        unsigned long nr_mfns)
> +static void __init create_mappings(lpae_t *second,
> +                                   unsigned long virt_offset,
> +                                   unsigned long base_mfn,
> +                                   unsigned long nr_mfns,
> +                                   unsigned int mapping_size)
>  {
>      unsigned long i, count;
> +    const unsigned long granularity = mapping_size >> PAGE_SHIFT;
>      lpae_t pte, *p;
> 
> -    ASSERT(!((virt_offset >> PAGE_SHIFT) % (16 * LPAE_ENTRIES)));
> -    ASSERT(!(base_mfn % (16 * LPAE_ENTRIES)));
> -    ASSERT(!(nr_mfns % (16 * LPAE_ENTRIES)));
> +    ASSERT((mapping_size == MB(2)) || (mapping_size == MB(32)));
> +    ASSERT(!((virt_offset >> PAGE_SHIFT) % granularity));
> +    ASSERT(!(base_mfn % granularity));
> +    ASSERT(!(nr_mfns % granularity));
> 
>      count = nr_mfns / LPAE_ENTRIES;
>      p = second + second_linear_offset(virt_offset);
>      pte = mfn_to_xen_entry(base_mfn, WRITEALLOC);
> -    pte.pt.contig = 1;  /* These maps are in 16-entry contiguous chunks. */
> +    if ( mapping_size == MB(32) )
> +        pte.pt.contig = 1;  /* These maps are in 16-entry contiguous
> + chunks. */
>      for ( i = 0; i < count; i++ )
>      {
>          write_pte(p + i, pte);
> @@ -660,7 +666,7 @@ static void __init create_32mb_mappings(lpae_t
> *second,  void __init setup_xenheap_mappings(unsigned long base_mfn,
>                                     unsigned long nr_mfns)  {
> -    create_32mb_mappings(xen_second, XENHEAP_VIRT_START, base_mfn,
> nr_mfns);
> +    create_mappings(xen_second, XENHEAP_VIRT_START, base_mfn,
> nr_mfns,
> + MB(32));
> 
>      /* Record where the xenheap is, for translation routines. */
>      xenheap_virt_end = XENHEAP_VIRT_START + nr_mfns * PAGE_SIZE; @@
> -749,6 +755,7 @@ void __init setup_frametable_mappings(paddr_t ps,
> paddr_t pe)
>      unsigned long nr_pdxs = pfn_to_pdx(nr_pages);
>      unsigned long frametable_size = nr_pdxs * sizeof(struct page_info);
>      unsigned long base_mfn;
> +    const unsigned long mapping_size = frametable_size < MB(32) ? MB(2)
> + : MB(32);
>  #ifdef CONFIG_ARM_64
>      lpae_t *second, pte;
>      unsigned long nr_second, second_base; @@ -756,9 +763,8 @@ void __init
> setup_frametable_mappings(paddr_t ps, paddr_t pe)  #endif
> 
>      frametable_base_pdx = pfn_to_pdx(ps >> PAGE_SHIFT);
> -
> -    /* Round up to 32M boundary */
> -    frametable_size = (frametable_size + 0x1ffffff) & ~0x1ffffff;
> +    /* Round up to 2M or 32M boundary, as appropriate. */
> +    frametable_size = ROUNDUP(frametable_size, mapping_size);
>      base_mfn = alloc_boot_pages(frametable_size >> PAGE_SHIFT, 32<<(20-
> 12));
> 
>  #ifdef CONFIG_ARM_64
> @@ -771,9 +777,10 @@ void __init setup_frametable_mappings(paddr_t ps,
> paddr_t pe)
>          pte.pt.table = 1;
>          write_pte(&xen_first[first_table_offset(FRAMETABLE_VIRT_START)+i],
> pte);
>      }
> -    create_32mb_mappings(second, 0, base_mfn, frametable_size >>
> PAGE_SHIFT);
> +    create_mappings(second, 0, base_mfn, frametable_size >> PAGE_SHIFT,
> + mapping_size);
>  #else
> -    create_32mb_mappings(xen_second, FRAMETABLE_VIRT_START,
> base_mfn, frametable_size >> PAGE_SHIFT);
> +    create_mappings(xen_second, FRAMETABLE_VIRT_START,
> +                    base_mfn, frametable_size >> PAGE_SHIFT,
> + mapping_size);
>  #endif
> 
>      memset(&frame_table[0], 0, nr_pdxs * sizeof(struct page_info));
> --
> 1.9.1


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