Re: [Xen-devel] [PATCH] libxc/arm: initialise p2m_size to make gcc happy

[Julien Grall <julien.grall@xxxxxxx>]

Hi,

On 03/14/2018 12:32 PM, Wei Liu wrote:
> Gcc with -O3 failed to spot the loop to initialise p2m_size runs at
> least once.
Aside, Andrew's comment the patch looks okay. But I am wondering why we 
need to allocate p2m_host for Arm?
From a quick look I have seen no real user except 
xc_dom_update_guest_p2m that can cope with p2m_host = NULL.
Cheers,

> Signed-off-by: Wei Liu <wei.liu2@xxxxxxxxxx>
> ---
>   tools/libxc/xc_dom_arm.c | 3 ++-
>   1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/tools/libxc/xc_dom_arm.c b/tools/libxc/xc_dom_arm.c
> index 5b9eca6087..97d08f055a 100644
> --- a/tools/libxc/xc_dom_arm.c
> +++ b/tools/libxc/xc_dom_arm.c
> @@ -395,7 +395,7 @@ static int meminit(struct xc_dom_image *dom)
>       const uint64_t modsize = dtb_size + ramdisk_size;
>       const uint64_t ram128mb = bankbase[0] + (128<<20);
>   
> -    xen_pfn_t p2m_size;
> +    xen_pfn_t p2m_size = 0; /* make gcc -O3 happy */
>       uint64_t bank0end;
>   
>       assert(dom->rambase_pfn << XC_PAGE_SHIFT == bankbase[0]);
> @@ -438,6 +438,7 @@ static int meminit(struct xc_dom_image *dom)
>   
>       assert(dom->rambank_size[0] != 0);
>       assert(ramsize == 0); /* Too much RAM is rejected above */
> +    assert(p2m_size != 0);
>   
>       dom->p2m_size = p2m_size;
>       dom->p2m_host = xc_dom_malloc(dom, sizeof(xen_pfn_t) * p2m_size);
--
Julien Grall

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