Re: [Qemu-devel] [RFC PATCH v1 2/4] exec.c: Remove static allocation of sub_section of sub_page

[Paolo Bonzini <pbonzini@redhat.com>]

On 13/06/2016 11:08, vijayak@caviumnetworks.com wrote:
> From: Vijaya Kumar K <Vijaya.Kumar@caviumnetworks.com>
> 
> Allocate sub_section dynamically. Remove dependency
> on TARGET_PAGE_SIZE to make run-time page size detection
> for arm platforms.
> 
> Signed-off-by: Vijaya Kumar K <vijayak@cavium.com>
> ---
>  exec.c |    5 +++--
>  1 file changed, 3 insertions(+), 2 deletions(-)
> 
> diff --git a/exec.c b/exec.c
> index a9d465b..e803a41 100644
> --- a/exec.c
> +++ b/exec.c
> @@ -154,7 +154,7 @@ typedef struct subpage_t {
>      MemoryRegion iomem;
>      AddressSpace *as;
>      hwaddr base;
> -    uint16_t sub_section[TARGET_PAGE_SIZE];
> +    uint16_t *sub_section;

Please make this a flexible array member instead, so that you can avoid
the extra pointer dereference.

Thanks,

Paolo

>  } subpage_t;
>  
>  #define PHYS_SECTION_UNASSIGNED 0
> @@ -1151,6 +1151,7 @@ static void phys_section_destroy(MemoryRegion *mr)
>      if (have_sub_page) {
>          subpage_t *subpage = container_of(mr, subpage_t, iomem);
>          object_unref(OBJECT(&subpage->iomem));
> +        g_free(subpage->sub_section);
>          g_free(subpage);
>      }
>  }
> @@ -2272,7 +2273,7 @@ static subpage_t *subpage_init(AddressSpace *as, hwaddr base)
>      subpage_t *mmio;
>  
>      mmio = g_malloc0(sizeof(subpage_t));
> -
> +    mmio->sub_section = g_malloc0(TARGET_PAGE_SIZE * sizeof(uint16_t));
>      mmio->as = as;
>      mmio->base = base;
>      memory_region_init_io(&mmio->iomem, NULL, &subpage_ops, mmio,
>