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>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>

3 files changed, 8 insertions, 1 deletions

diff --git a/arch/x86/xen/Kconfig b/arch/x86/xen/Kconfig
index fdce49c7aff6..c31ee77e1ec1 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 126d8ce591ce..cabfa97f4674 100644
--- a/drivers/xen/Kconfig
+++ b/drivers/xen/Kconfig
@@ -206,4 +206,7 @@ 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 d6886d90ccfd..a56776dbe095 100644
--- a/drivers/xen/balloon.c
+++ b/drivers/xen/balloon.c
@@ -359,6 +359,7 @@ static enum bp_state increase_reservation(unsigned long nr_pages)
 
                 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)) {
                         int ret;
@@ -368,6 +369,7 @@ static enum bp_state increase_reservation(unsigned long nr_pages)
                                 0);
                         BUG_ON(ret);
                 }
+#endif
 
                 /* Relinquish the page back to the allocator. */
                 ClearPageReserved(page);
@@ -416,13 +418,14 @@ 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)) {
                         ret = HYPERVISOR_update_va_mapping(
                                 (unsigned long)__va(pfn << PAGE_SHIFT),
                                 __pte_ma(0), 0);
                         BUG_ON(ret);
                 }
-
+#endif
         }
 
         /* Ensure that ballooned highmem pages don't have kmaps. */