static void vbg_guest_mappings_init()

in vboxguest/vboxguest_core.c [47:125]

• 54 lines of code
• 12 McCabe index (conditional complexity)

static void vbg_guest_mappings_init(struct vbg_dev *gdev)
{
	struct vmmdev_hypervisorinfo *req;
	void *guest_mappings[GUEST_MAPPINGS_TRIES];
	struct page **pages = NULL;
	u32 size, hypervisor_size;
	int i, rc;

	/* Query the required space. */
	req = vbg_req_alloc(sizeof(*req), VMMDEVREQ_GET_HYPERVISOR_INFO,
			    VBG_KERNEL_REQUEST);
	if (!req)
		return;

	req->hypervisor_start = 0;
	req->hypervisor_size = 0;
	rc = vbg_req_perform(gdev, req);
	if (rc < 0)
		goto out;

	/*
	 * The VMM will report back if there is nothing it wants to map, like
	 * for instance in VT-x and AMD-V mode.
	 */
	if (req->hypervisor_size == 0)
		goto out;

	hypervisor_size = req->hypervisor_size;
	/* Add 4M so that we can align the vmap to 4MiB as the host requires. */
	size = PAGE_ALIGN(req->hypervisor_size) + SZ_4M;

	pages = kmalloc_array(size >> PAGE_SHIFT, sizeof(*pages), GFP_KERNEL);
	if (!pages)
		goto out;

	gdev->guest_mappings_dummy_page = alloc_page(GFP_HIGHUSER);
	if (!gdev->guest_mappings_dummy_page)
		goto out;

	for (i = 0; i < (size >> PAGE_SHIFT); i++)
		pages[i] = gdev->guest_mappings_dummy_page;

	/*
	 * Try several times, the VMM might not accept some addresses because
	 * of address clashes between the three contexts.
	 */
	for (i = 0; i < GUEST_MAPPINGS_TRIES; i++) {
		guest_mappings[i] = vmap(pages, (size >> PAGE_SHIFT),
					 VM_MAP, PAGE_KERNEL_RO);
		if (!guest_mappings[i])
			break;

		req->header.request_type = VMMDEVREQ_SET_HYPERVISOR_INFO;
		req->header.rc = VERR_INTERNAL_ERROR;
		req->hypervisor_size = hypervisor_size;
		req->hypervisor_start =
			(unsigned long)PTR_ALIGN(guest_mappings[i], SZ_4M);

		rc = vbg_req_perform(gdev, req);
		if (rc >= 0) {
			gdev->guest_mappings = guest_mappings[i];
			break;
		}
	}

	/* Free vmap's from failed attempts. */
	while (--i >= 0)
		vunmap(guest_mappings[i]);

	/* On failure free the dummy-page backing the vmap */
	if (!gdev->guest_mappings) {
		__free_page(gdev->guest_mappings_dummy_page);
		gdev->guest_mappings_dummy_page = NULL;
	}

out:
	vbg_req_free(req, sizeof(*req));
	kfree(pages);
}