KVM: X86: Introduce kvm_mmu_slot_lpages() helpers

Introduce kvm_mmu_slot_lpages() to calculcate lpage_info and rmap array size.
The other __kvm_mmu_slot_lpages() can take an extra parameter of npages rather
than fetching from the memslot pointer.  Start to use the latter one in
kvm_alloc_memslot_metadata().
Signed-off-by: Peter Xu <peterx@redhat.com>
Message-Id: <20210730220455.26054-4-peterx@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

arch/x86/include/asm/kvm_host.h

@@ -124,13 +124,6 @@
 #define KVM_HPAGE_MASK(x)	(~(KVM_HPAGE_SIZE(x) - 1))
 #define KVM_PAGES_PER_HPAGE(x)	(KVM_HPAGE_SIZE(x) / PAGE_SIZE)
 
-static inline gfn_t gfn_to_index(gfn_t gfn, gfn_t base_gfn, int level)
-{
-	/* KVM_HPAGE_GFN_SHIFT(PG_LEVEL_4K) must be 0. */
-	return (gfn >> KVM_HPAGE_GFN_SHIFT(level)) -
-		(base_gfn >> KVM_HPAGE_GFN_SHIFT(level));
-}
-
 #define KVM_PERMILLE_MMU_PAGES 20
 #define KVM_MIN_ALLOC_MMU_PAGES 64UL
 #define KVM_MMU_HASH_SHIFT 12

arch/x86/kvm/mmu.h

@@ -240,4 +240,25 @@ static inline bool kvm_memslots_have_rmaps(struct kvm *kvm)
 	return smp_load_acquire(&kvm->arch.memslots_have_rmaps);
 }
 
+static inline gfn_t gfn_to_index(gfn_t gfn, gfn_t base_gfn, int level)
+{
+	/* KVM_HPAGE_GFN_SHIFT(PG_LEVEL_4K) must be 0. */
+	return (gfn >> KVM_HPAGE_GFN_SHIFT(level)) -
+		(base_gfn >> KVM_HPAGE_GFN_SHIFT(level));
+}
+
+static inline unsigned long
+__kvm_mmu_slot_lpages(struct kvm_memory_slot *slot, unsigned long npages,
+		      int level)
+{
+	return gfn_to_index(slot->base_gfn + npages - 1,
+			    slot->base_gfn, level) + 1;
+}
+
+static inline unsigned long
+kvm_mmu_slot_lpages(struct kvm_memory_slot *slot, int level)
+{
+	return __kvm_mmu_slot_lpages(slot, slot->npages, level);
+}
+
 #endif

arch/x86/kvm/mmu/page_track.c

@@ -16,6 +16,7 @@
 
 #include <asm/kvm_page_track.h>
 
+#include "mmu.h"
 #include "mmu_internal.h"
 
 void kvm_page_track_free_memslot(struct kvm_memory_slot *slot)

arch/x86/kvm/x86.c

@@ -11349,8 +11349,7 @@ static int memslot_rmap_alloc(struct kvm_memory_slot *slot,
 
 	for (i = 0; i < KVM_NR_PAGE_SIZES; ++i) {
 		int level = i + 1;
-		int lpages = gfn_to_index(slot->base_gfn + npages - 1,
-					  slot->base_gfn, level) + 1;
+		int lpages = __kvm_mmu_slot_lpages(slot, npages, level);
 
 		WARN_ON(slot->arch.rmap[i]);
 
@@ -11433,8 +11432,7 @@ static int kvm_alloc_memslot_metadata(struct kvm *kvm,
 		int lpages;
 		int level = i + 1;
 
-		lpages = gfn_to_index(slot->base_gfn + npages - 1,
-				      slot->base_gfn, level) + 1;
+		lpages = __kvm_mmu_slot_lpages(slot, npages, level);
 
 		linfo = kvcalloc(lpages, sizeof(*linfo), GFP_KERNEL_ACCOUNT);
 		if (!linfo)