Drivers: hv: vmbus: Cleanup hv_post_message()

Minimize failures in this function by pre-allocating the buffer
for posting messages. The hypercall for posting the message can fail
for a number of reasons:

        1. Transient resource related issues
        2. Buffer alignment
        3. Buffer cannot span a page boundry

We address issues 2 and 3 by preallocating a per-cpu page for the buffer.
Transient resource related failures are handled by retrying by the callers
of this function.

This patch is based on the investigation
done by Dexuan Cui <decui@microsoft.com>.

I would like to thank Sitsofe Wheeler <sitsofe@yahoo.com>
for reporting the issue and helping in debuggging.

Signed-off-by: K. Y. Srinivasan <kys@microsoft.com>
Reported-by: Sitsofe Wheeler <sitsofe@yahoo.com>
Cc: <stable@vger.kernel.org>
Tested-by: Sitsofe Wheeler <sitsofe@yahoo.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/hv/hv.c b/drivers/hv/hv.c
index edfc8488cb0358dd9bd9c6066166069ebce2aef8..3e4235c7a47fd30697b4c6d1e9b37b3bf55b7e6b 100644 (file)
--- a/drivers/hv/hv.c
+++ b/drivers/hv/hv.c
@@ -138,6 +138,8 @@ int hv_init(void)
        memset(hv_context.synic_event_page, 0, sizeof(void *) * NR_CPUS);
        memset(hv_context.synic_message_page, 0,
               sizeof(void *) * NR_CPUS);
+       memset(hv_context.post_msg_page, 0,
+              sizeof(void *) * NR_CPUS);
        memset(hv_context.vp_index, 0,
               sizeof(int) * NR_CPUS);
        memset(hv_context.event_dpc, 0,
@@ -217,26 +219,18 @@ int hv_post_message(union hv_connection_id connection_id,
                  enum hv_message_type message_type,
                  void *payload, size_t payload_size)
 {
-       struct aligned_input {
-               u64 alignment8;
-               struct hv_input_post_message msg;
-       };
 
        struct hv_input_post_message *aligned_msg;
        u16 status;
-       unsigned long addr;
 
        if (payload_size > HV_MESSAGE_PAYLOAD_BYTE_COUNT)
                return -EMSGSIZE;
 
-       addr = (unsigned long)kmalloc(sizeof(struct aligned_input), GFP_ATOMIC);
-       if (!addr)
-               return -ENOMEM;
-
        aligned_msg = (struct hv_input_post_message *)
-                       (ALIGN(addr, HV_HYPERCALL_PARAM_ALIGN));
+                       hv_context.post_msg_page[get_cpu()];
 
        aligned_msg->connectionid = connection_id;
+       aligned_msg->reserved = 0;
        aligned_msg->message_type = message_type;
        aligned_msg->payload_size = payload_size;
        memcpy((void *)aligned_msg->payload, payload, payload_size);
@@ -244,8 +238,7 @@ int hv_post_message(union hv_connection_id connection_id,
        status = do_hypercall(HVCALL_POST_MESSAGE, aligned_msg, NULL)
                & 0xFFFF;
 
-       kfree((void *)addr);
-
+       put_cpu();
        return status;
 }
 
@@ -294,6 +287,14 @@ int hv_synic_alloc(void)
                        pr_err("Unable to allocate SYNIC event page\n");
                        goto err;
                }
+
+               hv_context.post_msg_page[cpu] =
+                       (void *)get_zeroed_page(GFP_ATOMIC);
+
+               if (hv_context.post_msg_page[cpu] == NULL) {
+                       pr_err("Unable to allocate post msg page\n");
+                       goto err;
+               }
        }
 
        return 0;
@@ -308,6 +309,8 @@ static void hv_synic_free_cpu(int cpu)
                free_page((unsigned long)hv_context.synic_event_page[cpu]);
        if (hv_context.synic_message_page[cpu])
                free_page((unsigned long)hv_context.synic_message_page[cpu]);
+       if (hv_context.post_msg_page[cpu])
+               free_page((unsigned long)hv_context.post_msg_page[cpu]);
 }
 
 void hv_synic_free(void)

diff --git a/drivers/hv/hyperv_vmbus.h b/drivers/hv/hyperv_vmbus.h
index 22b750749a39c90393012cac83db6ff4bbff64ad..c386d8dc7223a2103ca2904ffc0a90ef026c156d 100644 (file)
--- a/drivers/hv/hyperv_vmbus.h
+++ b/drivers/hv/hyperv_vmbus.h
@@ -515,6 +515,10 @@ struct hv_context {
         * per-cpu list of the channels based on their CPU affinity.
         */
        struct list_head percpu_list[NR_CPUS];
+       /*
+        * buffer to post messages to the host.
+        */
+       void *post_msg_page[NR_CPUS];
 };
 
 extern struct hv_context hv_context;