KVM: selftests: Add helpers to convert guest memory b/w private and shared

Add helpers to convert memory between private and shared via KVM's
memory attributes, as well as helpers to free/allocate guest_memfd memory
via fallocate().  Userspace, i.e. tests, is NOT required to do fallocate()
when converting memory, as the attributes are the single source of truth.
Provide allocate() helpers so that tests can mimic a userspace that frees
private memory on conversion, e.g. to prioritize memory usage over
performance.

Signed-off-by: Vishal Annapurve <vannapurve@google.com>
Co-developed-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-Id: <20231027182217.3615211-28-seanjc@google.com>
Reviewed-by: Fuad Tabba <tabba@google.com>
Tested-by: Fuad Tabba <tabba@google.com
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

diff --git a/tools/testing/selftests/kvm/include/kvm_util_base.h b/tools/testing/selftests/kvm/include/kvm_util_base.h
index 9f861182c02a8415f1998b216a96d161d73f7d98..1441fca6c273d47f2401da25f2a9e5660dc8556c 100644 (file)
--- a/tools/testing/selftests/kvm/include/kvm_util_base.h
+++ b/tools/testing/selftests/kvm/include/kvm_util_base.h
@@ -333,6 +333,54 @@ static inline void vm_enable_cap(struct kvm_vm *vm, uint32_t cap, uint64_t arg0)
        vm_ioctl(vm, KVM_ENABLE_CAP, &enable_cap);
 }
 
+static inline void vm_set_memory_attributes(struct kvm_vm *vm, uint64_t gpa,
+                                           uint64_t size, uint64_t attributes)
+{
+       struct kvm_memory_attributes attr = {
+               .attributes = attributes,
+               .address = gpa,
+               .size = size,
+               .flags = 0,
+       };
+
+       /*
+        * KVM_SET_MEMORY_ATTRIBUTES overwrites _all_ attributes.  These flows
+        * need significant enhancements to support multiple attributes.
+        */
+       TEST_ASSERT(!attributes || attributes == KVM_MEMORY_ATTRIBUTE_PRIVATE,
+                   "Update me to support multiple attributes!");
+
+       vm_ioctl(vm, KVM_SET_MEMORY_ATTRIBUTES, &attr);
+}
+
+
+static inline void vm_mem_set_private(struct kvm_vm *vm, uint64_t gpa,
+                                     uint64_t size)
+{
+       vm_set_memory_attributes(vm, gpa, size, KVM_MEMORY_ATTRIBUTE_PRIVATE);
+}
+
+static inline void vm_mem_set_shared(struct kvm_vm *vm, uint64_t gpa,
+                                    uint64_t size)
+{
+       vm_set_memory_attributes(vm, gpa, size, 0);
+}
+
+void vm_guest_mem_fallocate(struct kvm_vm *vm, uint64_t gpa, uint64_t size,
+                           bool punch_hole);
+
+static inline void vm_guest_mem_punch_hole(struct kvm_vm *vm, uint64_t gpa,
+                                          uint64_t size)
+{
+       vm_guest_mem_fallocate(vm, gpa, size, true);
+}
+
+static inline void vm_guest_mem_allocate(struct kvm_vm *vm, uint64_t gpa,
+                                        uint64_t size)
+{
+       vm_guest_mem_fallocate(vm, gpa, size, false);
+}
+
 void vm_enable_dirty_ring(struct kvm_vm *vm, uint32_t ring_size);
 const char *vm_guest_mode_string(uint32_t i);
 

diff --git a/tools/testing/selftests/kvm/lib/kvm_util.c b/tools/testing/selftests/kvm/lib/kvm_util.c
index b63500fca6272bb6843aeb63b5cb07a5ac155eae..cc6007abc4b1e5d748bf37bea71ffca5f286be16 100644 (file)
--- a/tools/testing/selftests/kvm/lib/kvm_util.c
+++ b/tools/testing/selftests/kvm/lib/kvm_util.c
@@ -1167,6 +1167,34 @@ void vm_mem_region_delete(struct kvm_vm *vm, uint32_t slot)
        __vm_mem_region_delete(vm, memslot2region(vm, slot), true);
 }
 
+void vm_guest_mem_fallocate(struct kvm_vm *vm, uint64_t base, uint64_t size,
+                           bool punch_hole)
+{
+       const int mode = FALLOC_FL_KEEP_SIZE | (punch_hole ? FALLOC_FL_PUNCH_HOLE : 0);
+       struct userspace_mem_region *region;
+       uint64_t end = base + size;
+       uint64_t gpa, len;
+       off_t fd_offset;
+       int ret;
+
+       for (gpa = base; gpa < end; gpa += len) {
+               uint64_t offset;
+
+               region = userspace_mem_region_find(vm, gpa, gpa);
+               TEST_ASSERT(region && region->region.flags & KVM_MEM_GUEST_MEMFD,
+                           "Private memory region not found for GPA 0x%lx", gpa);
+
+               offset = gpa - region->region.guest_phys_addr;
+               fd_offset = region->region.guest_memfd_offset + offset;
+               len = min_t(uint64_t, end - gpa, region->region.memory_size - offset);
+
+               ret = fallocate(region->region.guest_memfd, mode, fd_offset, len);
+               TEST_ASSERT(!ret, "fallocate() failed to %s at %lx (len = %lu), fd = %d, mode = %x, offset = %lx\n",
+                           punch_hole ? "punch hole" : "allocate", gpa, len,
+                           region->region.guest_memfd, mode, fd_offset);
+       }
+}
+
 /* Returns the size of a vCPU's kvm_run structure. */
 static int vcpu_mmap_sz(void)
 {