Expose KVM's memory slot interface on Linux

Author: nullpo-head

include/vmm.h

@@ -119,10 +119,29 @@ int vmm_cpu_set_state(vmm_vm_t vm, vmm_cpu_t cpu, int id, uint64_t value);
 typedef const void *vmm_uvaddr_t;
 typedef uint64_t vmm_gpaddr_t;
 
+
+/* TODO: Abstract memory map management in Linux KVM */
+#ifdef __APPLE__
+
 int vmm_memory_map(vmm_vm_t vm, vmm_uvaddr_t uva, vmm_gpaddr_t gpa, size_t size, int prot);
 int vmm_memory_unmap(vmm_vm_t vm, vmm_gpaddr_t gpa, size_t size);
 int vmm_memory_protect(vmm_vm_t vm, vmm_gpaddr_t gpa, size_t size, int prot);
 
+#elif __linux__
+
+#include <linux/kvm.h>
+typedef struct kvm_userspace_memory_region *vmm_memregion_t;
+
+int vmm_memregion_set(vmm_vm_t vm, uint32_t reg_slot, vmm_uvaddr_t uva, vmm_gpaddr_t gpa, size_t size, int prot);
+int vmm_memregion_unset(vmm_vm_t vm, uint32_t reg_slot);
+
+int vmm_memory_map(vmm_vm_t vm, vmm_uvaddr_t uva, vmm_gpaddr_t gpa, size_t size, int prot) __attribute__ ((warning ("vmm_memory_map is not fully supported for KVM")));
+int vmm_memory_unmap(vmm_vm_t vm, vmm_gpaddr_t gpa, size_t size) __attribute__ ((error ("vmm_memory_unmap is not supported for KVM")));
+int vmm_memory_protect(vmm_vm_t vm, vmm_gpaddr_t gpa, size_t size, int prot) __attribute__ ((error ("vmm_memory_protect is not supported for KVM")));
+
+#endif
+
+
 #ifdef __cplusplus
 }
 #endif

src/vmm_kvm.c

@@ -83,24 +83,42 @@ vmm_destroy(vmm_vm_t vm)
 
 int
 vmm_memory_map(vmm_vm_t vm, vmm_uvaddr_t uva, vmm_gpaddr_t gpa, size_t size, int prot)
+{
+  static uint32_t slot = 0;
+  return vmm_memregion_set(vm, slot++, uva, gpa, size, prot);
+}
+
+int
+vmm_memregion_set(vmm_vm_t vm, uint32_t reg_slot, vmm_uvaddr_t uva, vmm_gpaddr_t gpa, size_t size, int prot)
 {
   int valid_prots = PROT_READ | PROT_WRITE | PROT_EXEC;
 
   if (prot & ~valid_prots)
     return VMM_EINVAL;
-  if ((prot & PROT_EXEC) == 0)
+  if ((prot & PROT_EXEC) == 0) // Non-executable cannot be supported directly on KVM
     return VMM_EINVAL;
 
   struct kvm_userspace_memory_region region = {
-    .slot = 0, // FIXME
+    .slot = reg_slot,
     .flags = (prot & PROT_WRITE) == 0 ? KVM_MEM_READONLY : 0,
     .guest_phys_addr = gpa,
     .memory_size = size,
     .userspace_addr = (uint64_t)uva,
   };
-  int ret;
+  if (ioctl(vm->vmfd, KVM_SET_USER_MEMORY_REGION, &region) < 0)
+    return -errno;
 
-  if ((ret = ioctl(vm->vmfd, KVM_SET_USER_MEMORY_REGION, &region)) < 0)
+  return 0;
+}
+
+int
+vmm_memregion_unset(vmm_vm_t vm, uint32_t reg_slot)
+{
+  struct kvm_userspace_memory_region zero_region = {
+    .slot = reg_slot,
+    .memory_size = 0,
+  };
+  if (ioctl(vm->vmfd, KVM_SET_USER_MEMORY_REGION, &zero_region) < 0)
     return -errno;
 
   return 0;