[PATCH 2/9] do not use mem_hole anymore.

[Glauber Costa <glommer@redhat.com>]

memory holes are totally evil. Right now they work for some basic tests,
but had never been stressed enough. Using memory holes leaves open questions like:

* what happens if a area being registered span two slots?
* what happens if there is already data in the slots?

also, the code behaves badly if the piece to be removed lies in the boundaries of the
current slot. Luckily, we don't really need it. Remove it, and make sure we never hit it.


Signed-off-by: Glauber Costa <glommer@redhat.com>
---
 libkvm/libkvm.c |   69 +-----------------------------------------------------
 qemu/qemu-kvm.c |   13 +++++----
 2 files changed, 9 insertions(+), 73 deletions(-)

diff --git a/libkvm/libkvm.c b/libkvm/libkvm.c
index 63fbcba..e768e44 100644
--- a/libkvm/libkvm.c
+++ b/libkvm/libkvm.c
@@ -436,74 +436,9 @@ int kvm_is_allocated_mem(kvm_context_t kvm, unsigned long phys_start,
 	return 0;
 }
 
-int kvm_create_mem_hole(kvm_context_t kvm, unsigned long phys_start,
-			unsigned long len)
-{
-	int slot;
-	int r;
-	struct kvm_userspace_memory_region rmslot;
-	struct kvm_userspace_memory_region newslot1;
-	struct kvm_userspace_memory_region newslot2;
-
-	len = (len + PAGE_SIZE - 1) & PAGE_MASK;
-
-	slot = get_intersecting_slot(phys_start);
-	/* no need to create hole, as there is already hole */
-	if (slot == -1)
-		return 0;
-
-	memset(&rmslot, 0, sizeof(struct kvm_userspace_memory_region));
-	memset(&newslot1, 0, sizeof(struct kvm_userspace_memory_region));
-	memset(&newslot2, 0, sizeof(struct kvm_userspace_memory_region));
-
-	rmslot.guest_phys_addr = slots[slot].phys_addr;
-	rmslot.slot = slot;
-
-	newslot1.guest_phys_addr = slots[slot].phys_addr;
-	newslot1.memory_size = phys_start - slots[slot].phys_addr;
-	newslot1.slot = slot;
-	newslot1.userspace_addr = slots[slot].userspace_addr;
-	newslot1.flags = slots[slot].flags;
-
-	newslot2.guest_phys_addr = newslot1.guest_phys_addr +
-				   newslot1.memory_size + len;
-	newslot2.memory_size = slots[slot].phys_addr +
-			       slots[slot].len - newslot2.guest_phys_addr;
-	newslot2.userspace_addr = newslot1.userspace_addr +
-				  newslot1.memory_size;
-	newslot2.slot = get_free_slot(kvm);
-	newslot2.flags = newslot1.flags;
-
-	r = ioctl(kvm->vm_fd, KVM_SET_USER_MEMORY_REGION, &rmslot);
-	if (r == -1) {
-		fprintf(stderr, "kvm_create_mem_hole: %s\n", strerror(errno));
-		return -1;
-	}
-	free_slot(slot);
-
-	r = ioctl(kvm->vm_fd, KVM_SET_USER_MEMORY_REGION, &newslot1);
-	if (r == -1) {
-		fprintf(stderr, "kvm_create_mem_hole: %s\n", strerror(errno));
-		return -1;
-	}
-	register_slot(newslot1.slot, newslot1.guest_phys_addr,
-		      newslot1.memory_size, newslot1.userspace_addr,
-		      newslot1.flags);
-
-	r = ioctl(kvm->vm_fd, KVM_SET_USER_MEMORY_REGION, &newslot2);
-	if (r == -1) {
-		fprintf(stderr, "kvm_create_mem_hole: %s\n", strerror(errno));
-		return -1;
-	}
-	register_slot(newslot2.slot, newslot2.guest_phys_addr,
-		      newslot2.memory_size, newslot2.userspace_addr,
-		      newslot2.flags);
-	return 0;
-}
-
 int kvm_register_phys_mem(kvm_context_t kvm,
-			unsigned long phys_start, void *userspace_addr,
-			unsigned long len, int log)
+			  unsigned long phys_start, void *userspace_addr,
+			  unsigned long len, int log)
 {
 
 	struct kvm_userspace_memory_region memory = {
diff --git a/qemu/qemu-kvm.c b/qemu/qemu-kvm.c
index 58a6d4a..cff04c5 100644
--- a/qemu/qemu-kvm.c
+++ b/qemu/qemu-kvm.c
@@ -781,12 +781,13 @@ void kvm_cpu_register_physical_memory(target_phys_addr_t start_addr,
     r = kvm_is_allocated_mem(kvm_context, start_addr, size);
     if (r)
         return;
-    r = kvm_is_intersecting_mem(kvm_context, start_addr);
-    if (r)
-        kvm_create_mem_hole(kvm_context, start_addr, size);
-    r = kvm_register_phys_mem(kvm_context, start_addr,
-                              phys_ram_base + phys_offset,
-                              size, 0);
+        r = kvm_is_intersecting_mem(kvm_context, start_addr);
+    if (r) {
+        printf("Ignoring intersecting memory %llx (%lx)\n", start_addr, size);
+    } else
+        r = kvm_register_phys_mem(kvm_context, start_addr,
+                                  phys_ram_base + phys_offset,
+                                  size, 0);
     if (r < 0) {
         printf("kvm_cpu_register_physical_memory: failed\n");
         exit(1);
-- 
1.5.5.1