Re: [Xen-devel] [PATCH 4/4] x86/PoD: Command line option to prohibit any PoD operations

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 30.10.15 at 19:33, <andrew.cooper3@xxxxxxxxxx> wrote:
> --- a/xen/arch/x86/hvm/hvm.c
> +++ b/xen/arch/x86/hvm/hvm.c
> @@ -92,6 +92,9 @@ unsigned long __section(".bss.page_aligned")
>  static bool_t __initdata opt_hap_enabled = 1;
>  boolean_param("hap", opt_hap_enabled);
>  
> +bool_t opt_pod_enabled = 1;

__read_mostly?

> --- a/xen/common/memory.c
> +++ b/xen/common/memory.c
> @@ -818,6 +818,10 @@ long do_memory_op(unsigned long cmd, 
> XEN_GUEST_HANDLE_PARAM(void) arg)
>          if ( unlikely(start_extent >= reservation.nr_extents) )
>              return start_extent;
>  
> +        if ( unlikely(!opt_pod_enabled) &&
> +             (reservation.mem_flags & XENMEMF_populate_on_demand) )
> +            return start_extent;

A few lines down we can see that XENMEMF_populate_on_demand
gets honored only for XENMEM_populate_physmap. Perhaps you
shouldn't fail the other two which ignore the flag anyway? And
perhaps you should also fold this into the existing check?

Also I don't think this is going to build on ARM.

Jan


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