Re: [Xen-devel] [PATCH v4 13/18] x86/mem_sharing: Skip xen heap pages in memshr nominate

[Jan Beulich <jbeulich@xxxxxxxx>]

On 08.01.2020 18:14, Tamas K Lengyel wrote:
> Trying to share these would fail anyway, better to skip them early.
> 
> Signed-off-by: Tamas K Lengyel <tamas.lengyel@xxxxxxxxx>

Reviewed-by: Jan Beulich <jbeulich@xxxxxxxx>
albeit I wonder if this couldn't be further generalized by ...

> --- a/xen/arch/x86/mm/mem_sharing.c
> +++ b/xen/arch/x86/mm/mem_sharing.c
> @@ -852,6 +852,11 @@ static int nominate_page(struct domain *d, gfn_t gfn,
>      if ( !p2m_is_sharable(p2mt) )
>          goto out;
>  
> +    /* Skip xen heap pages */
> +    page = mfn_to_page(mfn);
> +    if ( !page || is_xen_heap_page(page) )
> +        goto out;

... checking for a zero type ref count (the only means to permit
a type change) here, and maybe also ->count_info to fit what
page_make_sharable() expects.

Jan

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