On CoCo VMs without confidential VMBus, the netvsc send and receive buffers must be made host-visible by decrypting them. These buffers are vmalloc'ed, but set_memory_decrypted()/encrypted() do not work on vmalloc'ed memory. This use case is (so far) unique to netvsc, so solve it locally rather than changing the set_memory() or allocation APIs.
Add vmbus_alloc_buffer()/vmbus_free_buffer() to the VMBus core. When the guest's isolation model requires it, allocate the buffer as a list of physically-contiguous chunks via alloc_pages_node(), starting at MAX_PAGE_ORDER and falling back to smaller orders so the allocation still succeeds under memory fragmentation. Each chunk is decrypted in place via set_memory_decrypted() on its direct-map address, and the chunks are then stitched into a single virtually-contiguous range with vmap(). Buffers that do not need decryption keep using vzalloc(). This approach minimizes scattering of decrypted 4 KiB pages through the kernel direct map and the resulting shattering of large page mappings. Use vmbus_establish_gpadl_caller_decrypted() so there is no attempt to decrypt the virtual address. At teardown, vunmap() the range and re-encrypt and free each chunk individually; any chunk that fails re-encryption is leaked to prevent accidentally freeing decrypted memory. Because vunmap() and set_memory_encrypted() must run in process context, replace the rcu_head/call_rcu() pair used to defer free_netvsc_device() with rcu_work/queue_rcu_work(). This also fixes a small race condition where the buffers may be accessed while being re-encrypted by moving the re-encryption after the RCU grace period. Signed-off-by: Kameron Carr <[email protected]> --- drivers/hv/channel.c | 158 ++++++++++++++++++++++++++++++++ drivers/net/hyperv/hyperv_net.h | 8 +- drivers/net/hyperv/netvsc.c | 104 ++++++++++++++------- drivers/net/hyperv/netvsc_drv.c | 6 ++ include/linux/hyperv.h | 7 ++ 5 files changed, 249 insertions(+), 34 deletions(-) diff --git a/drivers/hv/channel.c b/drivers/hv/channel.c index 4782f5070bba9..9fe7b1163b408 100644 --- a/drivers/hv/channel.c +++ b/drivers/hv/channel.c @@ -13,11 +13,13 @@ #include <linux/wait.h> #include <linux/mm.h> #include <linux/slab.h> +#include <linux/log2.h> #include <linux/module.h> #include <linux/hyperv.h> #include <linux/uio.h> #include <linux/interrupt.h> #include <linux/set_memory.h> +#include <linux/vmalloc.h> #include <linux/export.h> #include <asm/page.h> #include <asm/mshyperv.h> @@ -608,6 +610,162 @@ int vmbus_establish_gpadl_caller_decrypted(struct vmbus_channel *channel, } EXPORT_SYMBOL_GPL(vmbus_establish_gpadl_caller_decrypted); +/* + * vmbus_free_buffer - release a buffer allocated by vmbus_alloc_buffer(). + * + * @addr: buffer address, or NULL if none was allocated (e.g. cleanup from a + * failed allocation) + * @chunks: chunks array from vmbus_alloc_buffer(), or NULL + * @chunk_cnt: number of entries in @chunks + * + * When @chunks is NULL the buffer is a plain vzalloc() allocation. + * + * Otherwise tear down the vmap, and for each chunk re-encrypt and free + * the underlying pages. Any chunk that cannot be re-encrypted is leaked. + */ +void vmbus_free_buffer(void *addr, struct page **chunks, u32 chunk_cnt) +{ + u32 i; + + if (!chunks) { + vfree(addr); + return; + } + + vunmap(addr); + + for (i = 0; i < chunk_cnt; i++) { + unsigned long vaddr = + (unsigned long)page_address(chunks[i]); + unsigned int order = folio_order(page_folio(chunks[i])); + + if (set_memory_encrypted(vaddr, 1U << order)) + continue; + __free_pages(chunks[i], order); + } + + kvfree(chunks); +} +EXPORT_SYMBOL_GPL(vmbus_free_buffer); + +/* + * vmbus_alloc_buffer - allocate a virtually-contiguous buffer suitable for + * a GPADL, making it host-visible when required by the guest's isolation model. + * + * @channel: the channel the buffer will be attached to + * @size: requested buffer size in bytes (will be rounded up to PAGE_SIZE) + * @chunks_out: on success, set to the array of underlying chunks, or NULL when + * the buffer was allocated with vzalloc() + * @chunk_cnt_out: on success, set to the number of chunks + * + * Buffers not requiring decryption are allocated with vzalloc(). + * + * Buffers requiring decryption are allocated as a series of + * physically-contiguous chunks, starting at MAX_PAGE_ORDER and falling back to + * smaller orders on allocation failure. Each chunk is transitioned to + * host-visible via set_memory_decrypted() on its direct-map address, then all + * chunks are combined into a virtually-contiguous range via vmap(). + * + * Return: the buffer's virtual address, or NULL on failure. + */ +void *vmbus_alloc_buffer(struct vmbus_channel *channel, + u32 size, + struct page ***chunks_out, + u32 *chunk_cnt_out) +{ + u32 nr_pages = PFN_UP(size); + struct page **chunks = NULL; + struct page **pages = NULL; + unsigned int order; + u32 chunk_cnt = 0; + u32 page_idx = 0; + u32 remaining = nr_pages; + void *addr; + u32 i; + int ret; + + *chunks_out = NULL; + *chunk_cnt_out = 0; + + if (!nr_pages) + return NULL; + + /* If the buffer does not need to be decrypted, just use vzalloc() */ + if (!hv_is_isolation_supported() || channel->co_external_memory) + return vzalloc((unsigned long)nr_pages << PAGE_SHIFT); + + /* Worst case: every chunk is a single page. */ + chunks = kvmalloc_array(nr_pages, sizeof(*chunks), + GFP_KERNEL | __GFP_ZERO); + if (!chunks) + goto err; + + pages = kvmalloc_array(nr_pages, sizeof(*pages), GFP_KERNEL); + if (!pages) + goto err; + + /* + * @order monotonically decreases across iterations + * + * Use __GFP_NORETRY | __GFP_NOWARN to avoid OOM-killing, but try + * harder at order 0 since that is the final fallback. + */ + order = min(MAX_PAGE_ORDER, ilog2(nr_pages)); + while (remaining) { + struct page *page; + gfp_t gfp; + + order = min(order, ilog2(remaining)); + + for (;;) { + gfp = GFP_KERNEL | __GFP_ZERO; + if (order) + gfp |= __GFP_COMP | __GFP_NORETRY | __GFP_NOWARN; + page = alloc_pages_node(cpu_to_node(channel->target_cpu), + gfp, order); + if (page) + break; + if (!order) + goto err; + order--; + } + + ret = set_memory_decrypted((unsigned long)page_address(page), + 1U << order); + if (ret) { + /* + * set_memory_decrypted() failed; the page state is + * unknown so it must be leaked rather than freed. + */ + goto err; + } + + chunks[chunk_cnt++] = page; + + for (i = 0; i < (1U << order); i++) + pages[page_idx++] = page + i; + + remaining -= 1U << order; + } + + addr = vmap(pages, nr_pages, VM_MAP, pgprot_decrypted(PAGE_KERNEL)); + if (!addr) + goto err; + + memset(addr, 0, (unsigned long)nr_pages << PAGE_SHIFT); + + kvfree(pages); + *chunks_out = chunks; + *chunk_cnt_out = chunk_cnt; + return addr; + +err: + kvfree(pages); + vmbus_free_buffer(NULL, chunks, chunk_cnt); + return NULL; +} +EXPORT_SYMBOL_GPL(vmbus_alloc_buffer); + /** * request_arr_init - Allocates memory for the requestor array. Each slot * keeps track of the next available slot in the array. Initially, each diff --git a/drivers/net/hyperv/hyperv_net.h b/drivers/net/hyperv/hyperv_net.h index 7397c693f984a..4841367fdab2f 100644 --- a/drivers/net/hyperv/hyperv_net.h +++ b/drivers/net/hyperv/hyperv_net.h @@ -220,6 +220,8 @@ struct net_device_context; extern u32 netvsc_ring_bytes; +int netvsc_workqueue_init(void); +void netvsc_workqueue_destroy(void); struct netvsc_device *netvsc_device_add(struct hv_device *device, const struct netvsc_device_info *info); int netvsc_alloc_recv_comp_ring(struct netvsc_device *net_device, u32 q_idx); @@ -1158,6 +1160,8 @@ struct netvsc_device { /* Receive buffer allocated by us but manages by NetVSP */ void *recv_buf; u32 recv_buf_size; /* allocated bytes */ + struct page **recv_buf_chunks; + u32 recv_buf_chunk_cnt; struct vmbus_gpadl recv_buf_gpadl_handle; u32 recv_section_cnt; u32 recv_section_size; @@ -1166,6 +1170,8 @@ struct netvsc_device { /* Send buffer allocated by us */ void *send_buf; u32 send_buf_size; + struct page **send_buf_chunks; + u32 send_buf_chunk_cnt; struct vmbus_gpadl send_buf_gpadl_handle; u32 send_section_cnt; u32 send_section_size; @@ -1193,7 +1199,7 @@ struct netvsc_device { struct netvsc_channel chan_table[VRSS_CHANNEL_MAX]; - struct rcu_head rcu; + struct rcu_work rwork; }; /* NdisInitialize message */ diff --git a/drivers/net/hyperv/netvsc.c b/drivers/net/hyperv/netvsc.c index 59e95341f9b1e..1192929d93a86 100644 --- a/drivers/net/hyperv/netvsc.c +++ b/drivers/net/hyperv/netvsc.c @@ -28,6 +28,8 @@ #include "hyperv_net.h" #include "netvsc_trace.h" +static struct workqueue_struct *netvsc_wq; + /* * Switch the data path from the synthetic interface to the VF * interface. @@ -125,6 +127,47 @@ static void netvsc_subchan_work(struct work_struct *w) rtnl_unlock(); } +static void __free_netvsc_device(struct netvsc_device *nvdev) +{ + int i; + + kfree(nvdev->extension); + + vmbus_free_buffer(nvdev->recv_buf, nvdev->recv_buf_chunks, + nvdev->recv_buf_chunk_cnt); + vmbus_free_buffer(nvdev->send_buf, nvdev->send_buf_chunks, + nvdev->send_buf_chunk_cnt); + bitmap_free(nvdev->send_section_map); + + for (i = 0; i < VRSS_CHANNEL_MAX; i++) { + xdp_rxq_info_unreg(&nvdev->chan_table[i].xdp_rxq); + kfree(nvdev->chan_table[i].recv_buf); + vfree(nvdev->chan_table[i].mrc.slots); + } + + kfree(nvdev); +} + +static void free_netvsc_device(struct work_struct *w) +{ + struct rcu_work *rwork = to_rcu_work(w); + + __free_netvsc_device(container_of(rwork, struct netvsc_device, rwork)); +} + +int netvsc_workqueue_init(void) +{ + netvsc_wq = alloc_workqueue("hv_netvsc", WQ_UNBOUND, 0); + + return netvsc_wq ? 0 : -ENOMEM; +} + +void netvsc_workqueue_destroy(void) +{ + rcu_barrier(); + destroy_workqueue(netvsc_wq); +} + static struct netvsc_device *alloc_net_device(void) { struct netvsc_device *net_device; @@ -143,36 +186,18 @@ static struct netvsc_device *alloc_net_device(void) init_completion(&net_device->channel_init_wait); init_waitqueue_head(&net_device->subchan_open); INIT_WORK(&net_device->subchan_work, netvsc_subchan_work); + INIT_RCU_WORK(&net_device->rwork, free_netvsc_device); return net_device; } -static void free_netvsc_device(struct rcu_head *head) -{ - struct netvsc_device *nvdev - = container_of(head, struct netvsc_device, rcu); - int i; - - kfree(nvdev->extension); - - if (!nvdev->recv_buf_gpadl_handle.decrypted) - vfree(nvdev->recv_buf); - if (!nvdev->send_buf_gpadl_handle.decrypted) - vfree(nvdev->send_buf); - bitmap_free(nvdev->send_section_map); - - for (i = 0; i < VRSS_CHANNEL_MAX; i++) { - xdp_rxq_info_unreg(&nvdev->chan_table[i].xdp_rxq); - kfree(nvdev->chan_table[i].recv_buf); - vfree(nvdev->chan_table[i].mrc.slots); - } - - kfree(nvdev); -} - static void free_netvsc_device_rcu(struct netvsc_device *nvdev) { - call_rcu(&nvdev->rcu, free_netvsc_device); + /* + * Defer the actual free to process context: vunmap() and + * set_memory_encrypted() cannot run from RCU softirq context. + */ + queue_rcu_work(netvsc_wq, &nvdev->rwork); } static void netvsc_revoke_recv_buf(struct hv_device *device, @@ -351,7 +376,11 @@ 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); + net_device->recv_buf = + vmbus_alloc_buffer(device->channel, buf_size, + &net_device->recv_buf_chunks, + &net_device->recv_buf_chunk_cnt); + if (!net_device->recv_buf) { netdev_err(ndev, "unable to allocate receive buffer of size %u\n", @@ -367,9 +396,10 @@ static int netvsc_init_buf(struct hv_device *device, * channel. Note: This call uses the vmbus connection rather * than the channel to establish the gpadl handle. */ - ret = vmbus_establish_gpadl(device->channel, net_device->recv_buf, - buf_size, - &net_device->recv_buf_gpadl_handle); + ret = vmbus_establish_gpadl_caller_decrypted(device->channel, + net_device->recv_buf, + buf_size, + &net_device->recv_buf_gpadl_handle); if (ret != 0) { netdev_err(ndev, "unable to establish receive buffer's gpadl\n"); @@ -457,7 +487,10 @@ 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); + net_device->send_buf = + vmbus_alloc_buffer(device->channel, buf_size, + &net_device->send_buf_chunks, + &net_device->send_buf_chunk_cnt); if (!net_device->send_buf) { netdev_err(ndev, "unable to allocate send buffer of size %u\n", buf_size); @@ -470,9 +503,10 @@ static int netvsc_init_buf(struct hv_device *device, * channel. Note: This call uses the vmbus connection rather * than the channel to establish the gpadl handle. */ - ret = vmbus_establish_gpadl(device->channel, net_device->send_buf, - buf_size, - &net_device->send_buf_gpadl_handle); + ret = vmbus_establish_gpadl_caller_decrypted(device->channel, + net_device->send_buf, + buf_size, + &net_device->send_buf_gpadl_handle); if (ret != 0) { netdev_err(ndev, "unable to establish send buffer's gpadl\n"); @@ -1863,7 +1897,11 @@ struct netvsc_device *netvsc_device_add(struct hv_device *device, netif_napi_del(&net_device->chan_table[0].napi); cleanup2: - free_netvsc_device(&net_device->rcu); + /* + * net_device was never published, so we don't need to wait for an + * RCU grace period -- call the free routine synchronously. + */ + __free_netvsc_device(net_device); return ERR_PTR(ret); } diff --git a/drivers/net/hyperv/netvsc_drv.c b/drivers/net/hyperv/netvsc_drv.c index ee5ab5ceb2be2..1d43c73fd73f1 100644 --- a/drivers/net/hyperv/netvsc_drv.c +++ b/drivers/net/hyperv/netvsc_drv.c @@ -2867,12 +2867,17 @@ static void __exit netvsc_drv_exit(void) { unregister_netdevice_notifier(&netvsc_netdev_notifier); vmbus_driver_unregister(&netvsc_drv); + netvsc_workqueue_destroy(); } static int __init netvsc_drv_init(void) { int ret; + ret = netvsc_workqueue_init(); + if (ret) + return ret; + if (ring_size < RING_SIZE_MIN) { ring_size = RING_SIZE_MIN; pr_info("Increased ring_size to %u (min allowed)\n", @@ -2890,6 +2895,7 @@ static int __init netvsc_drv_init(void) err_vmbus_reg: unregister_netdevice_notifier(&netvsc_netdev_notifier); + netvsc_workqueue_destroy(); return ret; } diff --git a/include/linux/hyperv.h b/include/linux/hyperv.h index 1146addbb42c4..f843ee0efa22f 100644 --- a/include/linux/hyperv.h +++ b/include/linux/hyperv.h @@ -1214,6 +1214,13 @@ extern int vmbus_establish_gpadl_caller_decrypted(struct vmbus_channel *channel, extern int vmbus_teardown_gpadl(struct vmbus_channel *channel, struct vmbus_gpadl *gpadl); +extern void *vmbus_alloc_buffer(struct vmbus_channel *channel, + u32 size, + struct page ***chunks_out, + u32 *chunk_cnt_out); + +extern void vmbus_free_buffer(void *addr, struct page **chunks, u32 chunk_cnt); + void vmbus_reset_channel_cb(struct vmbus_channel *channel); extern int vmbus_recvpacket(struct vmbus_channel *channel, -- 2.45.4
