[PATCH gmem 1/5] KVM: selftests: Rework fallocate() helper to work across multiple memslots

[Sean Christopherson <seanjc@google.com>]

Rework vm_guest_mem_fallocate() to play nice with ranges that cover more
than one memslot.  Converting a range that covers multiple memslots is
most definitely an interesting testcase, and there's no reason to force
the caller to manually shatter the range, especially since the size of
the region might not be known by the caller.

Signed-off-by: Sean Christopherson <seanjc@google.com>
---
 tools/testing/selftests/kvm/lib/kvm_util.c | 34 ++++++++++++----------
 1 file changed, 18 insertions(+), 16 deletions(-)

diff --git a/tools/testing/selftests/kvm/lib/kvm_util.c b/tools/testing/selftests/kvm/lib/kvm_util.c
index 8fc70c021c1c..33bc2c6be970 100644
--- a/tools/testing/selftests/kvm/lib/kvm_util.c
+++ b/tools/testing/selftests/kvm/lib/kvm_util.c
@@ -1206,30 +1206,32 @@ 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,
+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 = gpa + size - 1;
+	uint64_t end = base + size;
+	uint64_t gpa, len;
 	off_t fd_offset;
-	int mode, ret;
+	int 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);
+	for (gpa = base; gpa < end; gpa += len) {
+		uint64_t offset;
 
-	TEST_ASSERT(region == userspace_mem_region_find(vm, end, end),
-		    "fallocate() for guest_memfd must act on a single memslot");
+		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);
 
-	fd_offset = region->region.gmem_offset +
-		    (gpa - region->region.guest_phys_addr);
+		offset = (gpa - region->region.guest_phys_addr);
+		fd_offset = region->region.gmem_offset + offset;
+		len = min_t(uint64_t, end - gpa, region->region.memory_size - offset);
 
-	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);
+		ret = fallocate(region->region.gmem_fd, 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.gmem_fd, mode, fd_offset);
+	}
 }
 
 /* Returns the size of a vCPU's kvm_run structure. */
-- 
2.42.0.758.gaed0368e0e-goog