Re: [Xen-devel] [PATCH 08/14] xen: balloon: allow PVMMU interfaces to be compiled out

[Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>]

On Thu, 4 Oct 2012, Ian Campbell wrote:
> The ARM platform has no concept of PVMMU and therefor no
> HYPERVISOR_update_va_mapping et al. Allow this code to be compiled out
> when not required.
> 
> Signed-off-by: Ian Campbell <ian.campbell@xxxxxxxxxx>

I am unsure whether it is worth a new symbol and two ifdef's


>  arch/x86/xen/Kconfig  |    1 +
>  drivers/xen/Kconfig   |    3 +++
>  drivers/xen/balloon.c |    4 ++++
>  3 files changed, 8 insertions(+), 0 deletions(-)
> 
> diff --git a/arch/x86/xen/Kconfig b/arch/x86/xen/Kconfig
> index fdce49c..c31ee77 100644
> --- a/arch/x86/xen/Kconfig
> +++ b/arch/x86/xen/Kconfig
> @@ -6,6 +6,7 @@ config XEN
>       bool "Xen guest support"
>       select PARAVIRT
>       select PARAVIRT_CLOCK
> +     select XEN_HAVE_PVMMU
>       depends on X86_64 || (X86_32 && X86_PAE && !X86_VISWS)
>       depends on X86_CMPXCHG && X86_TSC
>       help
> diff --git a/drivers/xen/Kconfig b/drivers/xen/Kconfig
> index d4dffcd..9c00652 100644
> --- a/drivers/xen/Kconfig
> +++ b/drivers/xen/Kconfig
> @@ -204,4 +204,7 @@ config XEN_MCE_LOG
>         Allow kernel fetching MCE error from Xen platform and
>         converting it into Linux mcelog format for mcelog tools
>  
> +config XEN_HAVE_PVMMU
> +       bool
> +
>  endmenu
> diff --git a/drivers/xen/balloon.c b/drivers/xen/balloon.c
> index 1b56ae0..cfe47dae 100644
> --- a/drivers/xen/balloon.c
> +++ b/drivers/xen/balloon.c
> @@ -360,6 +360,7 @@ static enum bp_state increase_reservation(unsigned long 
> nr_pages)
>               if (!xen_feature(XENFEAT_auto_translated_physmap))
>                       set_phys_to_machine(pfn, frame_list[i]);
>  
> +#ifdef CONFIG_XEN_HAVE_PVMMU
>               /* Link back into the page tables if not highmem. */
>               if (xen_pv_domain() && !PageHighMem(page) && 
>                   !xen_feature(XENFEAT_auto_translated_physmap)) {
> @@ -371,6 +372,7 @@ static enum bp_state increase_reservation(unsigned long 
> nr_pages)
>                               0);
>                       BUG_ON(ret);
>               }
> +#endif
>  
>               /* Relinquish the page back to the allocator. */
>               ClearPageReserved(page);
> @@ -419,6 +421,7 @@ static enum bp_state decrease_reservation(unsigned long 
> nr_pages, gfp_t gfp)
>  
>               scrub_page(page);
>  
> +#ifdef CONFIG_XEN_HAVE_PVMMU
>               if (xen_pv_domain() && !PageHighMem(page) &&
>                   !xen_feature(XENFEAT_auto_translated_physmap)) {
>                               ret = HYPERVISOR_update_va_mapping(
> @@ -426,6 +429,7 @@ static enum bp_state decrease_reservation(unsigned long 
> nr_pages, gfp_t gfp)
>                                       __pte_ma(0), 0);
>                               BUG_ON(ret);
>               }
> +#endif
>       }
>  
>       /* Ensure that ballooned highmem pages don't have kmaps. */
> -- 
> 1.7.2.5
> 

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