KVM: Introduce kvm_memory_slot::arch and move lpage_info into it

Some members of kvm_memory_slot are not used by every architecture.

This patch is the first step to make this difference clear by
introducing kvm_memory_slot::arch;  lpage_info is moved into it.

Signed-off-by: Takuya Yoshikawa <yoshikawa.takuya@oss.ntt.co.jp>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
Signed-off-by: Avi Kivity <avi@redhat.com>

diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index c24125c..74c9edf 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -483,6 +483,15 @@
 	} osvw;
 };
 
+struct kvm_lpage_info {
+	unsigned long rmap_pde;
+	int write_count;
+};
+
+struct kvm_arch_memory_slot {
+	struct kvm_lpage_info *lpage_info[KVM_NR_PAGE_SIZES - 1];
+};
+
 struct kvm_arch {
 	unsigned int n_used_mmu_pages;
 	unsigned int n_requested_mmu_pages;