Xen devel - Oct 2012 - [PATCH 1/6] xen: balloon: allow PVMMU interfaces to be compiled out

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.

In some similar situations (e.g. P2M) we have defined dummy functions
to avoid this, however I think we can/should draw the line at dummying
out actual hypercalls.

Signed-off-by: Ian Campbell <ian.campbell@citrix.com>
---
 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 9323b8c..6d101a1 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 db3aa34..92449a0 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)) {
 			if (!xen_feature(XENFEAT_auto_translated_physmap)) {
 				ret = HYPERVISOR_update_va_mapping(
@@ -427,6 +430,7 @@ static enum bp_state decrease_reservation(unsigned long
nr_pages, gfp_t gfp)
 				BUG_ON(ret);
 			}
 		}
+#endif
 	}
 
 	/* Ensure that ballooned highmem pages don''t have kmaps. */
-- 
1.7.2.5

On Wed, 17 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.
> 
> In some similar situations (e.g. P2M) we have defined dummy functions
> to avoid this, however I think we can/should draw the line at dummying
> out actual hypercalls.
> 
> Signed-off-by: Ian Campbell <ian.campbell@citrix.com>
It is OK for me

>  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 9323b8c..6d101a1 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 db3aa34..92449a0 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)) {
>  			if (!xen_feature(XENFEAT_auto_translated_physmap)) {
>  				ret = HYPERVISOR_update_va_mapping(
> @@ -427,6 +430,7 @@ static enum bp_state decrease_reservation(unsigned long
nr_pages, gfp_t gfp)
>  				BUG_ON(ret);
>  			}
>  		}
> +#endif
>  	}
>  
>  	/* Ensure that ballooned highmem pages don''t have kmaps. */
> -- 
> 1.7.2.5
>