On Sun, May 30, 2021 at 11:06:27AM -0400, Tianyu Lan wrote:

+	if (hv_isolation_type_snp()) {
+		pfns = kcalloc(buf_size / HV_HYP_PAGE_SIZE, sizeof(unsigned long),
+			       GFP_KERNEL);
+		for (i = 0; i < buf_size / HV_HYP_PAGE_SIZE; i++)
+			pfns[i] = virt_to_hvpfn(net_device->recv_buf + i * HV_HYP_PAGE_SIZE) +
+				(ms_hyperv.shared_gpa_boundary >> HV_HYP_PAGE_SHIFT);
+
+		vaddr = vmap_pfn(pfns, buf_size / HV_HYP_PAGE_SIZE, PAGE_KERNEL_IO);
+		kfree(pfns);
+		if (!vaddr)
+			goto cleanup;
+		net_device->recv_original_buf = net_device->recv_buf;
+		net_device->recv_buf = vaddr;
+	}

This probably wnats a helper to make the thing more readable.  But who
came up with this fucked up communication protocol where the host needs
to map random pfns into a contigous range?  Sometime I really have to
wonder what crack the hyper-v people take when comparing this to the
relatively sane approach others take.

+	for (i = 0; i < page_count; i++)
+		dma_unmap_single(&hv_dev->device, packet->dma_range[i].dma,
+				 packet->dma_range[i].mapping_size,
+				 DMA_TO_DEVICE);
+
+	kfree(packet->dma_range);

Any reason this isn't simply using a struct scatterlist?

+	for (i = 0; i < page_count; i++) {
+		char *src = phys_to_virt((pb[i].pfn << HV_HYP_PAGE_SHIFT)
+					 + pb[i].offset);
+		u32 len = pb[i].len;
+
+		dma = dma_map_single(&hv_dev->device, src, len,
+				     DMA_TO_DEVICE);

dma_map_single can only be used on page baked memory, and if this is
using page backed memory you wouldn't need to do thee phys_to_virt
tricks.  Can someone explain the mess here in more detail?

 	struct rndis_device *dev = nvdev->extension;
 	struct rndis_request *request = NULL;
+	struct hv_device *hv_dev = ((struct net_device_context *)
+			netdev_priv(ndev))->device_ctx;

Why not use a net_device_context local variable instead of this cast
galore?