kvm: Introduce support for memory_attributes

Introduce the helper functions to set the attributes of a range of
memory to private or shared.

This is necessary to notify KVM the private/shared attribute of each gpa
range. KVM needs the information to decide the GPA needs to be mapped at
hva-based shared memory or guest_memfd based private memory.

Signed-off-by: Xiaoyao Li <xiaoyao.li@intel.com>
Message-ID: <20240320083945.991426-11-michael.roth@amd.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

accel/kvm/kvm-all.c

@@ -91,6 +91,7 @@ bool kvm_msi_use_devid;
 static bool kvm_has_guest_debug;
 static int kvm_sstep_flags;
 static bool kvm_immediate_exit;
+static uint64_t kvm_supported_memory_attributes;
 static hwaddr kvm_max_slot_size = ~0;
 
 static const KVMCapabilityInfo kvm_required_capabilites[] = {
@@ -1266,6 +1267,36 @@ void kvm_set_max_memslot_size(hwaddr max_slot_size)
     kvm_max_slot_size = max_slot_size;
 }
 
+static int kvm_set_memory_attributes(hwaddr start, uint64_t size, uint64_t attr)
+{
+    struct kvm_memory_attributes attrs;
+    int r;
+
+    assert((attr & kvm_supported_memory_attributes) == attr);
+    attrs.attributes = attr;
+    attrs.address = start;
+    attrs.size = size;
+    attrs.flags = 0;
+
+    r = kvm_vm_ioctl(kvm_state, KVM_SET_MEMORY_ATTRIBUTES, &attrs);
+    if (r) {
+        error_report("failed to set memory (0x%" HWADDR_PRIx "+0x%" PRIx64 ") "
+                     "with attr 0x%" PRIx64 " error '%s'",
+                     start, size, attr, strerror(errno));
+    }
+    return r;
+}
+
+int kvm_set_memory_attributes_private(hwaddr start, uint64_t size)
+{
+    return kvm_set_memory_attributes(start, size, KVM_MEMORY_ATTRIBUTE_PRIVATE);
+}
+
+int kvm_set_memory_attributes_shared(hwaddr start, uint64_t size)
+{
+    return kvm_set_memory_attributes(start, size, 0);
+}
+
 /* Called with KVMMemoryListener.slots_lock held */
 static void kvm_set_phys_mem(KVMMemoryListener *kml,
                              MemoryRegionSection *section, bool add)
@@ -2387,6 +2418,7 @@ static int kvm_init(MachineState *ms)
         goto err;
     }
 
+    kvm_supported_memory_attributes = kvm_check_extension(s, KVM_CAP_MEMORY_ATTRIBUTES);
     kvm_immediate_exit = kvm_check_extension(s, KVM_CAP_IMMEDIATE_EXIT);
     s->nr_slots = kvm_check_extension(s, KVM_CAP_NR_MEMSLOTS);
 

include/sysemu/kvm.h

@@ -536,4 +536,8 @@ void kvm_mark_guest_state_protected(void);
  * reported for the VM.
  */
 bool kvm_hwpoisoned_mem(void);
+
+int kvm_set_memory_attributes_private(hwaddr start, uint64_t size);
+int kvm_set_memory_attributes_shared(hwaddr start, uint64_t size);
+
 #endif