RE: [PATCH V4 12/13] hv_netvsc: Add Isolation VM support for netvsc driver

From: Michael Kelley
Date: Wed Sep 01 2021 - 22:34:34 EST

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From: Tianyu Lan <ltykernel@xxxxxxxxx> Sent: Friday, August 27, 2021 10:21 AM
>
> In Isolation VM, all shared memory with host needs to mark visible
> to host via hvcall. vmbus_establish_gpadl() has already done it for
> netvsc rx/tx ring buffer. The page buffer used by vmbus_sendpacket_
> pagebuffer() stills need to be handled. Use DMA API to map/umap
> these memory during sending/receiving packet and Hyper-V swiotlb
> bounce buffer dma adress will be returned. The swiotlb bounce buffer
> has been masked to be visible to host during boot up.
>
> Signed-off-by: Tianyu Lan <Tianyu.Lan@xxxxxxxxxxxxx>
> ---
> Change since v3:
> * Add comment to explain why not to use dma_map_sg()
> * Fix some error handle.
> ---
> arch/x86/hyperv/ivm.c | 1 +
> drivers/net/hyperv/hyperv_net.h | 5 ++
> drivers/net/hyperv/netvsc.c | 135 +++++++++++++++++++++++++++++-
> drivers/net/hyperv/rndis_filter.c | 2 +
> include/linux/hyperv.h | 5 ++
> 5 files changed, 145 insertions(+), 3 deletions(-)
>
> diff --git a/arch/x86/hyperv/ivm.c b/arch/x86/hyperv/ivm.c
> index 84563b3c9f3a..08d8e01de017 100644
> --- a/arch/x86/hyperv/ivm.c
> +++ b/arch/x86/hyperv/ivm.c
> @@ -317,6 +317,7 @@ void *hv_map_memory(void *addr, unsigned long size)
>
> return vaddr;
> }
> +EXPORT_SYMBOL_GPL(hv_map_memory);
>
> void hv_unmap_memory(void *addr)
> {
> diff --git a/drivers/net/hyperv/hyperv_net.h b/drivers/net/hyperv/hyperv_net.h
> index aa7c9962dbd8..862419912bfb 100644
> --- a/drivers/net/hyperv/hyperv_net.h
> +++ b/drivers/net/hyperv/hyperv_net.h
> @@ -164,6 +164,7 @@ struct hv_netvsc_packet {
> u32 total_bytes;
> u32 send_buf_index;
> u32 total_data_buflen;
> + struct hv_dma_range *dma_range;
> };
>
> #define NETVSC_HASH_KEYLEN 40
> @@ -1074,6 +1075,7 @@ struct netvsc_device {
>
> /* Receive buffer allocated by us but manages by NetVSP */
> void *recv_buf;
> + void *recv_original_buf;
> u32 recv_buf_size; /* allocated bytes */
> u32 recv_buf_gpadl_handle;
> u32 recv_section_cnt;
> @@ -1082,6 +1084,7 @@ struct netvsc_device {
>
> /* Send buffer allocated by us */
> void *send_buf;
> + void *send_original_buf;
> u32 send_buf_size;
> u32 send_buf_gpadl_handle;
> u32 send_section_cnt;
> @@ -1731,4 +1734,6 @@ struct rndis_message {
> #define RETRY_US_HI 10000
> #define RETRY_MAX 2000 /* >10 sec */
>
> +void netvsc_dma_unmap(struct hv_device *hv_dev,
> + struct hv_netvsc_packet *packet);
> #endif /* _HYPERV_NET_H */
> diff --git a/drivers/net/hyperv/netvsc.c b/drivers/net/hyperv/netvsc.c
> index f19bffff6a63..edd336b08c2c 100644
> --- a/drivers/net/hyperv/netvsc.c
> +++ b/drivers/net/hyperv/netvsc.c
> @@ -153,8 +153,21 @@ static void free_netvsc_device(struct rcu_head *head)
> int i;
>
> kfree(nvdev->extension);
> - vfree(nvdev->recv_buf);
> - vfree(nvdev->send_buf);
> +
> + if (nvdev->recv_original_buf) {
> + vunmap(nvdev->recv_buf);

In patch 11, you have added a hv_unmap_memory()
function as the inverse of hv_map_memory(). Since this
buffer was mapped with hv_map_memory() and you have
added that function, the cleanup should use
hv_unmap_memory() rather than calling vunmap() directly.

> + vfree(nvdev->recv_original_buf);
> + } else {
> + vfree(nvdev->recv_buf);
> + }
> +
> + if (nvdev->send_original_buf) {
> + vunmap(nvdev->send_buf);

Same here.

> + vfree(nvdev->send_original_buf);
> + } else {
> + vfree(nvdev->send_buf);
> + }
> +
> kfree(nvdev->send_section_map);
>
> for (i = 0; i < VRSS_CHANNEL_MAX; i++) {
> @@ -347,6 +360,7 @@ static int netvsc_init_buf(struct hv_device *device,
> unsigned int buf_size;
> size_t map_words;
> int i, ret = 0;
> + void *vaddr;
>
> /* Get receive buffer area. */
> buf_size = device_info->recv_sections * device_info->recv_section_size;
> @@ -382,6 +396,17 @@ static int netvsc_init_buf(struct hv_device *device,
> goto cleanup;
> }
>
> + if (hv_isolation_type_snp()) {
> + vaddr = hv_map_memory(net_device->recv_buf, buf_size);

Since the netvsc driver is architecture neutral, this code also needs
to compile for ARM64. A stub will be needed for hv_map_memory()
on the ARM64 side. Same for hv_unmap_memory() as suggested
above. Or better, move hv_map_memory() and hv_unmap_memory()
to an architecture neutral module such as hv_common.c.

Or if Christop's approach of creating the vmap_phys_addr() helper
comes to fruition, that's an even better approach since it will already
handle multiple architectures.

> + if (!vaddr) {
> + ret = -ENOMEM;
> + goto cleanup;
> + }
> +
> + net_device->recv_original_buf = net_device->recv_buf;
> + net_device->recv_buf = vaddr;
> + }
> +
> /* Notify the NetVsp of the gpadl handle */
> init_packet = &net_device->channel_init_pkt;
> memset(init_packet, 0, sizeof(struct nvsp_message));
> @@ -485,6 +510,17 @@ static int netvsc_init_buf(struct hv_device *device,
> goto cleanup;
> }
>
> + if (hv_isolation_type_snp()) {
> + vaddr = hv_map_memory(net_device->send_buf, buf_size);
> + if (!vaddr) {
> + ret = -ENOMEM;
> + goto cleanup;
> + }
> +
> + net_device->send_original_buf = net_device->send_buf;
> + net_device->send_buf = vaddr;
> + }
> +
> /* Notify the NetVsp of the gpadl handle */
> init_packet = &net_device->channel_init_pkt;
> memset(init_packet, 0, sizeof(struct nvsp_message));
> @@ -775,7 +811,7 @@ static void netvsc_send_tx_complete(struct net_device *ndev,
>
> /* Notify the layer above us */
> if (likely(skb)) {
> - const struct hv_netvsc_packet *packet
> + struct hv_netvsc_packet *packet
> = (struct hv_netvsc_packet *)skb->cb;
> u32 send_index = packet->send_buf_index;
> struct netvsc_stats *tx_stats;
> @@ -791,6 +827,7 @@ static void netvsc_send_tx_complete(struct net_device *ndev,
> tx_stats->bytes += packet->total_bytes;
> u64_stats_update_end(&tx_stats->syncp);
>
> + netvsc_dma_unmap(ndev_ctx->device_ctx, packet);
> napi_consume_skb(skb, budget);
> }
>
> @@ -955,6 +992,87 @@ static void netvsc_copy_to_send_buf(struct netvsc_device *net_device,
> memset(dest, 0, padding);
> }
>
> +void netvsc_dma_unmap(struct hv_device *hv_dev,
> + struct hv_netvsc_packet *packet)
> +{
> + u32 page_count = packet->cp_partial ?
> + packet->page_buf_cnt - packet->rmsg_pgcnt :
> + packet->page_buf_cnt;
> + int i;
> +
> + if (!hv_is_isolation_supported())
> + return;
> +
> + if (!packet->dma_range)
> + return;
> +
> + 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);
> +}
> +
> +/* netvsc_dma_map - Map swiotlb bounce buffer with data page of
> + * packet sent by vmbus_sendpacket_pagebuffer() in the Isolation
> + * VM.
> + *
> + * In isolation VM, netvsc send buffer has been marked visible to
> + * host and so the data copied to send buffer doesn't need to use
> + * bounce buffer. The data pages handled by vmbus_sendpacket_pagebuffer()
> + * may not be copied to send buffer and so these pages need to be
> + * mapped with swiotlb bounce buffer. netvsc_dma_map() is to do
> + * that. The pfns in the struct hv_page_buffer need to be converted
> + * to bounce buffer's pfn. The loop here is necessary becuase the

s/becuase/because/

> + * entries in the page buffer array are not necessarily full
> + * pages of data. Each entry in the array has a separate offset and
> + * len that may be non-zero, even for entries in the middle of the
> + * array. And the entries are not physically contiguous. So each
> + * entry must be individually mapped rather than as a contiguous unit.
> + * So not use dma_map_sg() here.
> + */
> +int netvsc_dma_map(struct hv_device *hv_dev,
> + struct hv_netvsc_packet *packet,
> + struct hv_page_buffer *pb)
> +{
> + u32 page_count = packet->cp_partial ?
> + packet->page_buf_cnt - packet->rmsg_pgcnt :
> + packet->page_buf_cnt;
> + dma_addr_t dma;
> + int i;
> +
> + if (!hv_is_isolation_supported())
> + return 0;
> +
> + packet->dma_range = kcalloc(page_count,
> + sizeof(*packet->dma_range),
> + GFP_KERNEL);
> + if (!packet->dma_range)
> + return -ENOMEM;
> +
> + 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);
> + if (dma_mapping_error(&hv_dev->device, dma)) {
> + kfree(packet->dma_range);
> + return -ENOMEM;
> + }
> +
> + packet->dma_range[i].dma = dma;
> + packet->dma_range[i].mapping_size = len;
> + pb[i].pfn = dma >> HV_HYP_PAGE_SHIFT;
> + pb[i].offset = offset_in_hvpage(dma);
> + pb[i].len = len;
> + }

Just to confirm, this driver does *not* set the DMA min_align_mask
like storvsc does. So after the call to dma_map_single(), the offset
in the page could be different. That's why you are updating
the pb[i].offset value. Alternatively, you could set the DMA
min_align_mask, which would ensure the offset is unchanged.
I'm OK with either approach, though perhaps a comment is
warranted to explain, as this is a subtle issue.

> +
> + return 0;
> +}
> +
> static inline int netvsc_send_pkt(
> struct hv_device *device,
> struct hv_netvsc_packet *packet,
> @@ -995,14 +1113,24 @@ static inline int netvsc_send_pkt(
>
> trace_nvsp_send_pkt(ndev, out_channel, rpkt);
>
> + packet->dma_range = NULL;
> if (packet->page_buf_cnt) {
> if (packet->cp_partial)
> pb += packet->rmsg_pgcnt;
>
> + ret = netvsc_dma_map(ndev_ctx->device_ctx, packet, pb);
> + if (ret) {
> + ret = -EAGAIN;
> + goto exit;
> + }
> +
> ret = vmbus_sendpacket_pagebuffer(out_channel,
> pb, packet->page_buf_cnt,
> &nvmsg, sizeof(nvmsg),
> req_id);
> +
> + if (ret)
> + netvsc_dma_unmap(ndev_ctx->device_ctx, packet);
> } else {
> ret = vmbus_sendpacket(out_channel,
> &nvmsg, sizeof(nvmsg),
> @@ -1010,6 +1138,7 @@ static inline int netvsc_send_pkt(
> VMBUS_DATA_PACKET_FLAG_COMPLETION_REQUESTED);
> }
>
> +exit:
> if (ret == 0) {
> atomic_inc_return(&nvchan->queue_sends);
>
> diff --git a/drivers/net/hyperv/rndis_filter.c b/drivers/net/hyperv/rndis_filter.c
> index f6c9c2a670f9..448fcc325ed7 100644
> --- a/drivers/net/hyperv/rndis_filter.c
> +++ b/drivers/net/hyperv/rndis_filter.c
> @@ -361,6 +361,8 @@ static void rndis_filter_receive_response(struct net_device *ndev,
> }
> }
>
> + netvsc_dma_unmap(((struct net_device_context *)
> + netdev_priv(ndev))->device_ctx, &request->pkt);
> complete(&request->wait_event);
> } else {
> netdev_err(ndev,
> diff --git a/include/linux/hyperv.h b/include/linux/hyperv.h
> index 724a735d722a..139a43ad65a1 100644
> --- a/include/linux/hyperv.h
> +++ b/include/linux/hyperv.h
> @@ -1596,6 +1596,11 @@ struct hyperv_service_callback {
> void (*callback)(void *context);
> };
>
> +struct hv_dma_range {
> + dma_addr_t dma;
> + u32 mapping_size;
> +};
> +
> #define MAX_SRV_VER 0x7ffffff
> extern bool vmbus_prep_negotiate_resp(struct icmsg_hdr *icmsghdrp, u8 *buf, u32 buflen,
> const int *fw_version, int fw_vercnt,
> --
> 2.25.1

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