Re: [PATCH V5 12/12] net: netvsc: Add Isolation VM support for netvsc driver

Tianyu Lan
2021-09-22T10:34:49Z

Hi Christoph:
This patch follows your purposal in the previous discussion.
Could you have a look?
"use vmap_pfn as in the current series. But in that case I think
we should get rid of the other mapping created by vmalloc. I
though a bit about finding a way to apply the offset in vmalloc
itself, but I think it would be too invasive to the normal fast
path. So the other sub-option would be to allocate the pages
manually (maybe even using high order allocations to reduce TLB
pressure) and then remap them(https://lkml.org/lkml/2021/9/2/112)

Otherwise, I merge your previous change for swiotlb into patch 9
“x86/Swiotlb: Add Swiotlb bounce buffer remap function for HV IVM”
You previous change
link.(http://git.infradead.org/users/hch/misc.git/commit/8248f295928aded3364a1e54a4e0022e93d3610c)
Please have a look.

Thanks.

On 9/16/2021 12:21 AM, Michael Kelley wrote:
> From: Tianyu Lan <ltykernel@gmail.com> Sent: Tuesday, September 14, 2021 6:39 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 address will be returned. The swiotlb bounce buffer
>> has been masked to be visible to host during boot up.
>>
>> Allocate rx/tx ring buffer via alloc_pages() in Isolation VM and map
>> these pages via vmap(). After calling vmbus_establish_gpadl() which
>> marks these pages visible to host, unmap these pages to release the
>> virtual address mapped with physical address below shared_gpa_boundary
>> and map them in the extra address space via vmap_pfn().
>>
>> Signed-off-by: Tianyu Lan <Tianyu.Lan@microsoft.com>
>> ---
>> Change since v4:
>> * Allocate rx/tx ring buffer via alloc_pages() in Isolation VM
>> * Map pages after calling vmbus_establish_gpadl().
>> * set dma_set_min_align_mask for netvsc driver.
>>
>> Change since v3:
>> * Add comment to explain why not to use dma_map_sg()
>> * Fix some error handle.
>> ---
>> drivers/net/hyperv/hyperv_net.h | 7 +
>> drivers/net/hyperv/netvsc.c | 287 +++++++++++++++++++++++++++++-
>> drivers/net/hyperv/netvsc_drv.c | 1 +
>> drivers/net/hyperv/rndis_filter.c | 2 +
>> include/linux/hyperv.h | 5 +
>> 5 files changed, 296 insertions(+), 6 deletions(-)
>>
>> diff --git a/drivers/net/hyperv/hyperv_net.h b/drivers/net/hyperv/hyperv_net.h
>> index 315278a7cf88..87e8c74398a5 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 +1075,8 @@ struct netvsc_device {
>>
>> /* Receive buffer allocated by us but manages by NetVSP */
>> void *recv_buf;
>> + struct page **recv_pages;
>> + u32 recv_page_count;
>> u32 recv_buf_size; /* allocated bytes */
>> struct vmbus_gpadl recv_buf_gpadl_handle;
>> u32 recv_section_cnt;
>> @@ -1082,6 +1085,8 @@ struct netvsc_device {
>>
>> /* Send buffer allocated by us */
>> void *send_buf;
>> + struct page **send_pages;
>> + u32 send_page_count;
>> u32 send_buf_size;
>> struct vmbus_gpadl send_buf_gpadl_handle;
>> u32 send_section_cnt;
>> @@ -1731,4 +1736,6 @@ 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 1f87e570ed2b..7d5254bf043e 100644
>> --- a/drivers/net/hyperv/netvsc.c
>> +++ b/drivers/net/hyperv/netvsc.c
>> @@ -20,6 +20,7 @@
>> #include <linux/vmalloc.h>
>> #include <linux/rtnetlink.h>
>> #include <linux/prefetch.h>
>> +#include <linux/gfp.h>
>>
>> #include <asm/sync_bitops.h>
>> #include <asm/mshyperv.h>
>> @@ -150,11 +151,33 @@ static void free_netvsc_device(struct rcu_head *head)
>> {
>> struct netvsc_device *nvdev
>> = container_of(head, struct netvsc_device, rcu);
>> + unsigned int alloc_unit;
>> int i;
>>
>> kfree(nvdev->extension);
>> - vfree(nvdev->recv_buf);
>> - vfree(nvdev->send_buf);
>> +
>> + if (nvdev->recv_pages) {
>> + alloc_unit = (nvdev->recv_buf_size /
>> + nvdev->recv_page_count) >> PAGE_SHIFT;
>> +
>> + vunmap(nvdev->recv_buf);
>> + for (i = 0; i < nvdev->recv_page_count; i++)
>> + __free_pages(nvdev->recv_pages[i], alloc_unit);
>> + } else {
>> + vfree(nvdev->recv_buf);
>> + }
>> +
>> + if (nvdev->send_pages) {
>> + alloc_unit = (nvdev->send_buf_size /
>> + nvdev->send_page_count) >> PAGE_SHIFT;
>> +
>> + vunmap(nvdev->send_buf);
>> + for (i = 0; i < nvdev->send_page_count; i++)
>> + __free_pages(nvdev->send_pages[i], alloc_unit);
>> + } else {
>> + vfree(nvdev->send_buf);
>> + }
>> +
>> kfree(nvdev->send_section_map);
>>
>> for (i = 0; i < VRSS_CHANNEL_MAX; i++) {
>> @@ -330,6 +353,108 @@ int netvsc_alloc_recv_comp_ring(struct netvsc_device *net_device, u32 q_idx)
>> return nvchan->mrc.slots ? 0 : -ENOMEM;
>> }
>>
>> +void *netvsc_alloc_pages(struct page ***pages_array, unsigned int *array_len,
>> + unsigned long size)
>> +{
>> + struct page *page, **pages, **vmap_pages;
>> + unsigned long pg_count = size >> PAGE_SHIFT;
>> + int alloc_unit = MAX_ORDER_NR_PAGES;
>> + int i, j, vmap_page_index = 0;
>> + void *vaddr;
>> +
>> + if (pg_count < alloc_unit)
>> + alloc_unit = 1;
>> +
>> + /* vmap() accepts page array with PAGE_SIZE as unit while try to
>> + * allocate high order pages here in order to save page array space.
>> + * vmap_pages[] is used as input parameter of vmap(). pages[] is to
>> + * store allocated pages and map them later.
>> + */
>> + vmap_pages = kmalloc_array(pg_count, sizeof(*vmap_pages), GFP_KERNEL);
>> + if (!vmap_pages)
>> + return NULL;
>> +
>> +retry:
>> + *array_len = pg_count / alloc_unit;
>> + pages = kmalloc_array(*array_len, sizeof(*pages), GFP_KERNEL);
>> + if (!pages)
>> + goto cleanup;
>> +
>> + for (i = 0; i < *array_len; i++) {
>> + page = alloc_pages(GFP_KERNEL | __GFP_ZERO,
>> + get_order(alloc_unit << PAGE_SHIFT));
>> + if (!page) {
>> + /* Try allocating small pages if high order pages are not available. */
>> + if (alloc_unit == 1) {
>> + goto cleanup;
>> + } else {
>
> The "else" clause isn't really needed because of the goto cleanup above. Then
> the indentation of the code below could be reduced by one level.
>
>> + memset(vmap_pages, 0,
>> + sizeof(*vmap_pages) * vmap_page_index);
>> + vmap_page_index = 0;
>> +
>> + for (j = 0; j < i; j++)
>> + __free_pages(pages[j], alloc_unit);
>> +
>> + kfree(pages);
>> + alloc_unit = 1;
>
> This is the case where a large enough contiguous physical memory chunk could
> not be found. But rather than dropping all the way down to single pages,
> would it make sense to try something smaller, but not 1? For example,
> cut the alloc_unit in half and try again. But I'm not sure of all the implications.
>
>> + goto retry;
>> + }
>> + }
>> +
>> + pages[i] = page;
>> + for (j = 0; j < alloc_unit; j++)
>> + vmap_pages[vmap_page_index++] = page++;
>> + }
>> +
>> + vaddr = vmap(vmap_pages, vmap_page_index, VM_MAP, PAGE_KERNEL);
>> + kfree(vmap_pages);
>> +
>> + *pages_array = pages;
>> + return vaddr;
>> +
>> +cleanup:
>> + for (j = 0; j < i; j++)
>> + __free_pages(pages[i], alloc_unit);
>> +
>> + kfree(pages);
>> + kfree(vmap_pages);
>> + return NULL;
>> +}
>> +
>> +static void *netvsc_map_pages(struct page **pages, int count, int alloc_unit)
>> +{
>> + int pg_count = count * alloc_unit;
>> + struct page *page;
>> + unsigned long *pfns;
>> + int pfn_index = 0;
>> + void *vaddr;
>> + int i, j;
>> +
>> + if (!pages)
>> + return NULL;
>> +
>> + pfns = kcalloc(pg_count, sizeof(*pfns), GFP_KERNEL);
>> + if (!pfns)
>> + return NULL;
>> +
>> + for (i = 0; i < count; i++) {
>> + page = pages[i];
>> + if (!page) {
>> + pr_warn("page is not available %d.\n", i);
>> + return NULL;
>> + }
>> +
>> + for (j = 0; j < alloc_unit; j++) {
>> + pfns[pfn_index++] = page_to_pfn(page++) +
>> + (ms_hyperv.shared_gpa_boundary >> PAGE_SHIFT);
>> + }
>> + }
>> +
>> + vaddr = vmap_pfn(pfns, pg_count, PAGE_KERNEL_IO);
>> + kfree(pfns);
>> + return vaddr;
>> +}
>> +
>
> I think you are proposing this approach to allocating memory for the send
> and receive buffers so that you can avoid having two virtual mappings for
> the memory, per comments from Christop Hellwig. But overall, the approach
> seems a bit complex and I wonder if it is worth it. If allocating large contiguous
> chunks of physical memory is successful, then there is some memory savings
> in that the data structures needed to keep track of the physical pages is
> smaller than the equivalent page tables might be. But if you have to revert
> to allocating individual pages, then the memory savings is reduced.
>
> Ultimately, the list of actual PFNs has to be kept somewhere. Another approach
> would be to do the reverse of what hv_map_memory() from the v4 patch
> series does. I.e., you could do virt_to_phys() on each virtual address that
> maps above VTOM, and subtract out the shared_gpa_boundary to get the
> list of actual PFNs that need to be freed. This way you don't have two copies
> of the list of PFNs -- one with and one without the shared_gpa_boundary added.
> But it comes at the cost of additional code so that may not be a great idea.
>
> I think what you have here works, and I don't have a clearly better solution
> at the moment except perhaps to revert to the v4 solution and just have two
> virtual mappings. I'll keep thinking about it. Maybe Christop has other
> thoughts.
>
>> static int netvsc_init_buf(struct hv_device *device,
>> struct netvsc_device *net_device,
>> const struct netvsc_device_info *device_info)
>> @@ -337,7 +462,7 @@ static int netvsc_init_buf(struct hv_device *device,
>> struct nvsp_1_message_send_receive_buffer_complete *resp;
>> struct net_device *ndev = hv_get_drvdata(device);
>> struct nvsp_message *init_packet;
>> - unsigned int buf_size;
>> + unsigned int buf_size, alloc_unit;
>> size_t map_words;
>> int i, ret = 0;
>>
>> @@ -350,7 +475,14 @@ static int netvsc_init_buf(struct hv_device *device,
>> buf_size = min_t(unsigned int, buf_size,
>> NETVSC_RECEIVE_BUFFER_SIZE_LEGACY);
>>
>> - net_device->recv_buf = vzalloc(buf_size);
>> + if (hv_isolation_type_snp())
>> + net_device->recv_buf =
>> + netvsc_alloc_pages(&net_device->recv_pages,
>> + &net_device->recv_page_count,
>> + buf_size);
>> + else
>> + net_device->recv_buf = vzalloc(buf_size);
>> +
>
> I wonder if it is necessary to have two different code paths here. The
> allocating and freeing of the send and receive buffers is not perf
> sensitive, and it seems like netvsc_alloc_pages() could be used
> regardless of whether SNP Isolation is in effect. To my thinking,
> one code path is better than two code paths unless there's a
> compelling reason to have two.
>
>> if (!net_device->recv_buf) {
>> netdev_err(ndev,
>> "unable to allocate receive buffer of size %u\n",
>> @@ -375,6 +507,27 @@ static int netvsc_init_buf(struct hv_device *device,
>> goto cleanup;
>> }
>>
>> + if (hv_isolation_type_snp()) {
>> + alloc_unit = (buf_size / net_device->recv_page_count)
>> + >> PAGE_SHIFT;
>> +
>> + /* Unmap previous virtual address and map pages in the extra
>> + * address space(above shared gpa boundary) in Isolation VM.
>> + */
>> + vunmap(net_device->recv_buf);
>> + net_device->recv_buf =
>> + netvsc_map_pages(net_device->recv_pages,
>> + net_device->recv_page_count,
>> + alloc_unit);
>> + if (!net_device->recv_buf) {
>> + netdev_err(ndev,
>> + "unable to allocate receive buffer of size %u\n",
>> + buf_size);
>> + ret = -ENOMEM;
>> + goto cleanup;
>> + }
>> + }
>> +
>> /* Notify the NetVsp of the gpadl handle */
>> init_packet = &net_device->channel_init_pkt;
>> memset(init_packet, 0, sizeof(struct nvsp_message));
>> @@ -456,13 +609,21 @@ static int netvsc_init_buf(struct hv_device *device,
>> buf_size = device_info->send_sections * device_info->send_section_size;
>> buf_size = round_up(buf_size, PAGE_SIZE);
>>
>> - net_device->send_buf = vzalloc(buf_size);
>> + if (hv_isolation_type_snp())
>> + net_device->send_buf =
>> + netvsc_alloc_pages(&net_device->send_pages,
>> + &net_device->send_page_count,
>> + buf_size);
>> + else
>> + net_device->send_buf = vzalloc(buf_size);
>> +
>> if (!net_device->send_buf) {
>> netdev_err(ndev, "unable to allocate send buffer of size %u\n",
>> buf_size);
>> ret = -ENOMEM;
>> goto cleanup;
>> }
>> +
>> net_device->send_buf_size = buf_size;
>>
>> /* Establish the gpadl handle for this buffer on this
>> @@ -478,6 +639,27 @@ static int netvsc_init_buf(struct hv_device *device,
>> goto cleanup;
>> }
>>
>> + if (hv_isolation_type_snp()) {
>> + alloc_unit = (buf_size / net_device->send_page_count)
>> + >> PAGE_SHIFT;
>> +
>> + /* Unmap previous virtual address and map pages in the extra
>> + * address space(above shared gpa boundary) in Isolation VM.
>> + */
>> + vunmap(net_device->send_buf);
>> + net_device->send_buf =
>> + netvsc_map_pages(net_device->send_pages,
>> + net_device->send_page_count,
>> + alloc_unit);
>> + if (!net_device->send_buf) {
>> + netdev_err(ndev,
>> + "unable to allocate receive buffer of size %u\n",
>> + buf_size);
>> + ret = -ENOMEM;
>> + goto cleanup;
>> + }
>> + }
>> +
>> /* Notify the NetVsp of the gpadl handle */
>> init_packet = &net_device->channel_init_pkt;
>> memset(init_packet, 0, sizeof(struct nvsp_message));
>> @@ -768,7 +950,7 @@ 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;
>> @@ -784,6 +966,7 @@ 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);
>> }
>>
>> @@ -948,6 +1131,87 @@ 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 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.
>> + */
>> +static 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);
>
> With the DMA min align mask now being set, the offset within
> the Hyper-V page won't be changed by dma_map_single(). So I
> think the above statement can be removed.
>
>> + pb[i].len = len;
>
> A few lines above, the value of "len" is set from pb[i].len. Neither
> "len" nor "i" is changed in the loop, so this statement can also be
> removed.
>
>> + }
>> +
>> + return 0;
>> +}
>> +
>> static inline int netvsc_send_pkt(
>> struct hv_device *device,
>> struct hv_netvsc_packet *packet,
>> @@ -988,14 +1252,24 @@ 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),
>> @@ -1003,6 +1277,7 @@ 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/netvsc_drv.c b/drivers/net/hyperv/netvsc_drv.c
>> index 382bebc2420d..c3dc884b31e3 100644
>> --- a/drivers/net/hyperv/netvsc_drv.c
>> +++ b/drivers/net/hyperv/netvsc_drv.c
>> @@ -2577,6 +2577,7 @@ static int netvsc_probe(struct hv_device *dev,
>> list_add(&net_device_ctx->list, &netvsc_dev_list);
>> rtnl_unlock();
>>
>> + dma_set_min_align_mask(&dev->device, HV_HYP_PAGE_SIZE - 1);
>> netvsc_devinfo_put(device_info);
>> return 0;
>>
>> 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 c94c534a944e..81e58dd582dc 100644
>> --- a/include/linux/hyperv.h
>> +++ b/include/linux/hyperv.h
>> @@ -1597,6 +1597,11 @@ 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
>