KVM: Integrate gfn_to_memslot_approx() into search_memslots()

s390 arch has gfn_to_memslot_approx() which is almost identical to
search_memslots(), differing only in that in case the gfn falls in a hole
one of the memslots bordering the hole is returned.

Add this lookup mode as an option to search_memslots() so we don't have two
almost identical functions for looking up a memslot by its gfn.

Signed-off-by: Maciej S. Szmigiero <maciej.szmigiero@oracle.com>
[sean: tweaked helper names to keep gfn_to_memslot_approx() in s390]
Reviewed-by: Sean Christopherson <seanjc@google.com>
Message-Id: <171cd89b52c718dbe180ecd909b4437a64a7e2ec.1638817640.git.maciej.szmigiero@oracle.com>

diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c
index 251059ff81fcb9dda60e01e65a0e531a2db15b6b..631be750af08b19508e451d8c693cfa9d6b847bc 100644 (file)
--- a/arch/s390/kvm/kvm-s390.c
+++ b/arch/s390/kvm/kvm-s390.c
@@ -1943,41 +1943,6 @@ out:
 /* for consistency */
 #define KVM_S390_CMMA_SIZE_MAX ((u32)KVM_S390_SKEYS_MAX)
 
-/*
- * Similar to gfn_to_memslot, but returns the index of a memslot also when the
- * address falls in a hole. In that case the index of one of the memslots
- * bordering the hole is returned.
- */
-static int gfn_to_memslot_approx(struct kvm_memslots *slots, gfn_t gfn)
-{
-       int start = 0, end = slots->used_slots;
-       int slot = atomic_read(&slots->last_used_slot);
-       struct kvm_memory_slot *memslots = slots->memslots;
-
-       if (gfn >= memslots[slot].base_gfn &&
-           gfn < memslots[slot].base_gfn + memslots[slot].npages)
-               return slot;
-
-       while (start < end) {
-               slot = start + (end - start) / 2;
-
-               if (gfn >= memslots[slot].base_gfn)
-                       end = slot;
-               else
-                       start = slot + 1;
-       }
-
-       if (start >= slots->used_slots)
-               return slots->used_slots - 1;
-
-       if (gfn >= memslots[start].base_gfn &&
-           gfn < memslots[start].base_gfn + memslots[start].npages) {
-               atomic_set(&slots->last_used_slot, start);
-       }
-
-       return start;
-}
-
 static int kvm_s390_peek_cmma(struct kvm *kvm, struct kvm_s390_cmma_log *args,
                              u8 *res, unsigned long bufsize)
 {
@@ -2001,11 +1966,17 @@ static int kvm_s390_peek_cmma(struct kvm *kvm, struct kvm_s390_cmma_log *args,
        return 0;
 }
 
+static struct kvm_memory_slot *gfn_to_memslot_approx(struct kvm_memslots *slots,
+                                                    gfn_t gfn)
+{
+       return ____gfn_to_memslot(slots, gfn, true);
+}
+
 static unsigned long kvm_s390_next_dirty_cmma(struct kvm_memslots *slots,
                                              unsigned long cur_gfn)
 {
-       int slotidx = gfn_to_memslot_approx(slots, cur_gfn);
-       struct kvm_memory_slot *ms = slots->memslots + slotidx;
+       struct kvm_memory_slot *ms = gfn_to_memslot_approx(slots, cur_gfn);
+       int slotidx = ms - slots->memslots;
        unsigned long ofs = cur_gfn - ms->base_gfn;
 
        if (ms->base_gfn + ms->npages <= cur_gfn) {

diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
index da0d4f21a150a72ed762503b2a86811a00aa283b..2f80ce84fbcf80dfbc590a3c440f42eb3ddafdb9 100644 (file)
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -1233,10 +1233,14 @@ try_get_memslot(struct kvm_memslots *slots, int slot_index, gfn_t gfn)
  * Returns a pointer to the memslot that contains gfn and records the index of
  * the slot in index. Otherwise returns NULL.
  *
+ * With "approx" set returns the memslot also when the address falls
+ * in a hole. In that case one of the memslots bordering the hole is
+ * returned.
+ *
  * IMPORTANT: Slots are sorted from highest GFN to lowest GFN!
  */
 static inline struct kvm_memory_slot *
-search_memslots(struct kvm_memslots *slots, gfn_t gfn, int *index)
+search_memslots(struct kvm_memslots *slots, gfn_t gfn, int *index, bool approx)
 {
        int start = 0, end = slots->used_slots;
        struct kvm_memory_slot *memslots = slots->memslots;
@@ -1254,22 +1258,26 @@ search_memslots(struct kvm_memslots *slots, gfn_t gfn, int *index)
                        start = slot + 1;
        }
 
+       if (approx && start >= slots->used_slots) {
+               *index = slots->used_slots - 1;
+               return &memslots[slots->used_slots - 1];
+       }
+
        slot = try_get_memslot(slots, start, gfn);
        if (slot) {
                *index = start;
                return slot;
        }
+       if (approx) {
+               *index = start;
+               return &memslots[start];
+       }
 
        return NULL;
 }
 
-/*
- * __gfn_to_memslot() and its descendants are here because it is called from
- * non-modular code in arch/powerpc/kvm/book3s_64_vio{,_hv}.c. gfn_to_memslot()
- * itself isn't here as an inline because that would bloat other code too much.
- */
 static inline struct kvm_memory_slot *
-__gfn_to_memslot(struct kvm_memslots *slots, gfn_t gfn)
+____gfn_to_memslot(struct kvm_memslots *slots, gfn_t gfn, bool approx)
 {
        struct kvm_memory_slot *slot;
        int slot_index = atomic_read(&slots->last_used_slot);
@@ -1278,7 +1286,7 @@ __gfn_to_memslot(struct kvm_memslots *slots, gfn_t gfn)
        if (slot)
                return slot;
 
-       slot = search_memslots(slots, gfn, &slot_index);
+       slot = search_memslots(slots, gfn, &slot_index, approx);
        if (slot) {
                atomic_set(&slots->last_used_slot, slot_index);
                return slot;
@@ -1287,6 +1295,17 @@ __gfn_to_memslot(struct kvm_memslots *slots, gfn_t gfn)
        return NULL;
 }
 
+/*
+ * __gfn_to_memslot() and its descendants are here to allow arch code to inline
+ * the lookups in hot paths.  gfn_to_memslot() itself isn't here as an inline
+ * because that would bloat other code too much.
+ */
+static inline struct kvm_memory_slot *
+__gfn_to_memslot(struct kvm_memslots *slots, gfn_t gfn)
+{
+       return ____gfn_to_memslot(slots, gfn, false);
+}
+
 static inline unsigned long
 __gfn_to_hva_memslot(const struct kvm_memory_slot *slot, gfn_t gfn)
 {

diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index 8ccb1ac82d38e8d679a5564dcfbdf7d820c9ae2d..6ca076ae64a28f714f0f84342353279474c57065 100644 (file)
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -2141,7 +2141,7 @@ struct kvm_memory_slot *kvm_vcpu_gfn_to_memslot(struct kvm_vcpu *vcpu, gfn_t gfn
         * search_memslots() instead of __gfn_to_memslot() to avoid
         * thrashing the VM-wide last_used_index in kvm_memslots.
         */
-       slot = search_memslots(slots, gfn, &slot_index);
+       slot = search_memslots(slots, gfn, &slot_index, false);
        if (slot) {
                vcpu->last_used_slot = slot_index;
                return slot;