[PATCH 1/1] KVM: Move kvm_gmem_migrate_folio inside CONFIG_MIGRATION

["'Guanjun'" <guanjun@xxxxxxxxxxxxxxxxx>]

From: Guanjun <guanjun@xxxxxxxxxxxxxxxxx>

'kvm_gmem_migrate_folio' is only used when CONFIG_MIGRATION
is defined, And it will triggers the compiler warning about
'kvm_gmem_migrate_folio' defined but not used when CONFIG_MIGRATION
isn't defined.

The compiler complained like that:
arch/x86/kvm/../../../virt/kvm/guest_memfd.c:262:12: error: ‘kvm_gmem_migrate_folio’ defined but not used [-Werror=unused-function]
  262 | static int kvm_gmem_migrate_folio(struct address_space *mapping,
      |            ^~~~~~~~~~~~~~~~~~~~~~

Fixes: a7800aa80ea4 (KVM: Add KVM_CREATE_GUEST_MEMFD ioctl() for guest-specific backing memory)
Signed-off-by: Guanjun <guanjun@xxxxxxxxxxxxxxxxx>
---
 virt/kvm/guest_memfd.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/virt/kvm/guest_memfd.c b/virt/kvm/guest_memfd.c
index 16d58806e913..62bb8a1a47d1 100644
--- a/virt/kvm/guest_memfd.c
+++ b/virt/kvm/guest_memfd.c
@@ -259,6 +259,7 @@ void kvm_gmem_init(struct module *module)
 	kvm_gmem_fops.owner = module;
 }
 
+#ifdef CONFIG_MIGRATION
 static int kvm_gmem_migrate_folio(struct address_space *mapping,
 				  struct folio *dst, struct folio *src,
 				  enum migrate_mode mode)
@@ -266,6 +267,7 @@ static int kvm_gmem_migrate_folio(struct address_space *mapping,
 	WARN_ON_ONCE(1);
 	return -EINVAL;
 }
+#endif
 
 static int kvm_gmem_error_folio(struct address_space *mapping,
 		struct folio *folio)
-- 
2.39.3