[RFC PATCH v12 25/33] KVM: selftests: Add helpers to convert guest memory b/w private and shared

[Sean Christopherson]

From: Vishal Annapurve <vannapurve at google.com>

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 true.
The fallocate() helpers are provided 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 at google.com>
Co-developed-by: Sean Christopherson <seanjc at google.com>
Signed-off-by: Sean Christopherson <seanjc at google.com>
---
 .../selftests/kvm/include/kvm_util_base.h     | 48 +++++++++++++++++++
 tools/testing/selftests/kvm/lib/kvm_util.c    | 26 ++++++++++
 2 files changed, 74 insertions(+)

diff --git a/tools/testing/selftests/kvm/include/kvm_util_base.h b/tools/testing/selftests/kvm/include/kvm_util_base.h
index 47ea25f9dc97..a0315503ac3e 100644
--- 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 127f44c6c83c..bf2bd5c39a96 100644
--- a/tools/testing/selftests/kvm/lib/kvm_util.c
+++ b/tools/testing/selftests/kvm/lib/kvm_util.c
@@ -1176,6 +1176,32 @@ 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 gpa, uint64_t size,
+			    bool punch_hole)
+{
+	struct userspace_mem_region *region;
+	uint64_t end = gpa + size - 1;
+	off_t fd_offset;
+	int mode, ret;
+
+	region = userspace_mem_region_find(vm, gpa, gpa);
+	TEST_ASSERT(region && region->region.flags & KVM_MEM_PRIVATE,
+		    "Private memory region not found for GPA 0x%lx", gpa);
+
+	TEST_ASSERT(region == userspace_mem_region_find(vm, end, end),
+		    "fallocate() for guest_memfd must act on a single memslot");
+
+	fd_offset = region->region.gmem_offset +
+		    (gpa - region->region.guest_phys_addr);
+
+	mode = FALLOC_FL_KEEP_SIZE | (punch_hole ? FALLOC_FL_PUNCH_HOLE : 0);
+
+	ret = fallocate(region->region.gmem_fd, mode, fd_offset, size);
+	TEST_ASSERT(!ret, "fallocate() failed to %s at %lx[%lu], fd = %d, mode = %x, offset = %lx\n",
+		     punch_hole ? "punch hole" : "allocate", gpa, size,
+		     region->region.gmem_fd, mode, fd_offset);
+}
+
 /* Returns the size of a vCPU's kvm_run structure. */
 static int vcpu_mmap_sz(void)
 {
-- 
2.42.0.283.g2d96d420d3-goog