Re: [PATCH V6 5/5] net: netvsc: Add Isolation VM support for netvsc driver

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On 12/9/2021 4:14 AM, Haiyang Zhang wrote:
From: Tianyu Lan <ltykernel@xxxxxxxxx>
Sent: Tuesday, December 7, 2021 2:56 AM
To: KY Srinivasan <kys@xxxxxxxxxxxxx>; Haiyang Zhang <haiyangz@xxxxxxxxxxxxx>; Stephen
Hemminger <sthemmin@xxxxxxxxxxxxx>; wei.liu@xxxxxxxxxx; Dexuan Cui <decui@xxxxxxxxxxxxx>;
tglx@xxxxxxxxxxxxx; mingo@xxxxxxxxxx; bp@xxxxxxxxx; dave.hansen@xxxxxxxxxxxxxxx;
x86@xxxxxxxxxx; hpa@xxxxxxxxx; davem@xxxxxxxxxxxxx; kuba@xxxxxxxxxx; jejb@xxxxxxxxxxxxx;
martin.petersen@xxxxxxxxxx; arnd@xxxxxxxx; hch@xxxxxxxxxxxxx; m.szyprowski@xxxxxxxxxxx;
robin.murphy@xxxxxxx; Tianyu Lan <Tianyu.Lan@xxxxxxxxxxxxx>; thomas.lendacky@xxxxxxx;
Michael Kelley (LINUX) <mikelley@xxxxxxxxxxxxx>
Cc: iommu@xxxxxxxxxxxxxxxxxxxxxxxxxx; linux-arch@xxxxxxxxxxxxxxx; linux-
hyperv@xxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx; linux-scsi@xxxxxxxxxxxxxxx;
netdev@xxxxxxxxxxxxxxx; vkuznets <vkuznets@xxxxxxxxxx>; brijesh.singh@xxxxxxx;
konrad.wilk@xxxxxxxxxx; hch@xxxxxx; joro@xxxxxxxxxx; parri.andrea@xxxxxxxxx;
dave.hansen@xxxxxxxxx
Subject: [PATCH V6 5/5] net: netvsc: Add Isolation VM support for netvsc driver

From: Tianyu Lan <Tianyu.Lan@xxxxxxxxxxxxx>

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 address will be returned. The swiotlb bounce buffer
has been masked to be visible to host during boot up.

rx/tx ring buffer is allocated via vzalloc() and they need to be
mapped into unencrypted address space(above vTOM) before sharing
with host and accessing. Add hv_map/unmap_memory() to map/umap rx
/tx ring buffer.

Signed-off-by: Tianyu Lan <Tianyu.Lan@xxxxxxxxxxxxx>
---
Change since v3:
        * Replace HV_HYP_PAGE_SIZE with PAGE_SIZE and virt_to_hvpfn()
          with vmalloc_to_pfn() in the hv_map_memory()

Change since v2:
        * Add hv_map/unmap_memory() to map/umap rx/tx ring buffer.
---
  arch/x86/hyperv/ivm.c             |  28 ++++++
  drivers/hv/hv_common.c            |  11 +++
  drivers/net/hyperv/hyperv_net.h   |   5 ++
  drivers/net/hyperv/netvsc.c       | 136 +++++++++++++++++++++++++++++-
  drivers/net/hyperv/netvsc_drv.c   |   1 +
  drivers/net/hyperv/rndis_filter.c |   2 +
  include/asm-generic/mshyperv.h    |   2 +
  include/linux/hyperv.h            |   5 ++
  8 files changed, 187 insertions(+), 3 deletions(-)

diff --git a/arch/x86/hyperv/ivm.c b/arch/x86/hyperv/ivm.c
index 69c7a57f3307..2b994117581e 100644
--- a/arch/x86/hyperv/ivm.c
+++ b/arch/x86/hyperv/ivm.c
@@ -287,3 +287,31 @@ int hv_set_mem_host_visibility(unsigned long kbuffer, int pagecount,
bool visibl
  	kfree(pfn_array);
  	return ret;
  }
+
+/*
+ * hv_map_memory - map memory to extra space in the AMD SEV-SNP Isolation VM.
+ */
+void *hv_map_memory(void *addr, unsigned long size)
+{
+	unsigned long *pfns = kcalloc(size / PAGE_SIZE,
+				      sizeof(unsigned long), GFP_KERNEL);
+	void *vaddr;
+	int i;
+
+	if (!pfns)
+		return NULL;
+
+	for (i = 0; i < size / PAGE_SIZE; i++)
+		pfns[i] = vmalloc_to_pfn(addr + i * PAGE_SIZE) +
+			(ms_hyperv.shared_gpa_boundary >> PAGE_SHIFT);
+
+	vaddr = vmap_pfn(pfns, size / PAGE_SIZE, PAGE_KERNEL_IO);
+	kfree(pfns);
+
+	return vaddr;
+}
+
+void hv_unmap_memory(void *addr)
+{
+	vunmap(addr);
+}
diff --git a/drivers/hv/hv_common.c b/drivers/hv/hv_common.c
index 7be173a99f27..3c5cb1f70319 100644
--- a/drivers/hv/hv_common.c
+++ b/drivers/hv/hv_common.c
@@ -295,3 +295,14 @@ u64 __weak hv_ghcb_hypercall(u64 control, void *input, void *output,
u32 input_s
  	return HV_STATUS_INVALID_PARAMETER;
  }
  EXPORT_SYMBOL_GPL(hv_ghcb_hypercall);
+
+void __weak *hv_map_memory(void *addr, unsigned long size)
+{
+	return NULL;
+}
+EXPORT_SYMBOL_GPL(hv_map_memory);
+
+void __weak hv_unmap_memory(void *addr)
+{
+}
+EXPORT_SYMBOL_GPL(hv_unmap_memory);
diff --git a/drivers/net/hyperv/hyperv_net.h b/drivers/net/hyperv/hyperv_net.h
index 315278a7cf88..cf69da0e296c 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 */
  	struct vmbus_gpadl 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;
  	struct vmbus_gpadl 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 396bc1c204e6..b7ade735a806 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) {
+		hv_unmap_memory(nvdev->recv_buf);
+		vfree(nvdev->recv_original_buf);
+	} else {
+		vfree(nvdev->recv_buf);
+	}
+
+	if (nvdev->send_original_buf) {
+		hv_unmap_memory(nvdev->send_buf);
+		vfree(nvdev->send_original_buf);
+	} else {
+		vfree(nvdev->send_buf);
+	}
+
  	kfree(nvdev->send_section_map);

  	for (i = 0; i < VRSS_CHANNEL_MAX; i++) {
@@ -338,6 +351,7 @@ 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;
@@ -373,6 +387,17 @@ 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);
+		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));
@@ -476,6 +501,17 @@ 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));
@@ -766,7 +802,7 @@ 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;
@@ -782,6 +818,7 @@ 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);
  	}

@@ -946,6 +983,88 @@ 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 because the
+ * 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;
+		}
+
+		/* pb[].offset and pb[].len are not changed during dma mapping
+		 * and so not reassign.
+		 */
+		packet->dma_range[i].dma = dma;
+		packet->dma_range[i].mapping_size = len;
+		pb[i].pfn = dma >> HV_HYP_PAGE_SHIFT;
+	}
+
+	return 0;
+}
+
  static inline int netvsc_send_pkt(
  	struct hv_device *device,
  	struct hv_netvsc_packet *packet,
@@ -986,14 +1105,24 @@ 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;
+		}

Returning EAGAIN will let the upper network layer busy retry,
which may make things worse.
I suggest to return ENOSPC here like another place in this
function, which will just drop the packet, and let the network
protocol/app layer decide how to recover.


Yes, agree. Will update in the next version. Thanks.




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