Drivers: hv: vmbus: Cleanup hv_post_message()

commit b29ef3546aecb253a5552b198cef23750d56e1e4 upstream.

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>
Tested-by: Sitsofe Wheeler <sitsofe@yahoo.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
[bwh: Backported to 3.2:
 - s/NR_CPUS/MAX_NUM_CPUS/
 - Adjust context, indentation
 - Also free the page in hv_synic_init() error path]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

diff --git a/drivers/hv/hv.c b/drivers/hv/hv.c
index 0fb100ed91a36a79910b0d7fec72c51ca1aa4264..17ed6fbb9b5647641fbfdaacc03798df81d8a07b 100644 (file)
--- a/drivers/hv/hv.c
+++ b/drivers/hv/hv.c
@@ -158,6 +158,8 @@ int hv_init(void)
        memset(hv_context.synic_event_page, 0, sizeof(void *) * MAX_NUM_CPUS);
        memset(hv_context.synic_message_page, 0,
               sizeof(void *) * MAX_NUM_CPUS);
+       memset(hv_context.post_msg_page, 0,
+              sizeof(void *) * MAX_NUM_CPUS);
 
        if (!query_hypervisor_presence())
                goto cleanup;
@@ -258,26 +260,18 @@ u16 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);
@@ -285,8 +279,7 @@ u16 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;
 }
 
@@ -347,6 +340,14 @@ void hv_synic_init(void *irqarg)
                goto cleanup;
        }
 
+       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 cleanup;
+       }
+
        /* Setup the Synic's message page */
        rdmsrl(HV_X64_MSR_SIMP, simp.as_uint64);
        simp.simp_enabled = 1;
@@ -388,6 +389,8 @@ cleanup:
 
        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]);
        return;
 }
 
@@ -426,4 +429,5 @@ void hv_synic_cleanup(void *arg)
 
        free_page((unsigned long)hv_context.synic_message_page[cpu]);
        free_page((unsigned long)hv_context.synic_event_page[cpu]);
+       free_page((unsigned long)hv_context.post_msg_page[cpu]);
 }

diff --git a/drivers/hv/hyperv_vmbus.h b/drivers/hv/hyperv_vmbus.h
index 0aee1122734c45df8a5b98732b52d3695dade69a..be2f3af70097cefc4d4e88c7b914c32a38586426 100644 (file)
--- a/drivers/hv/hyperv_vmbus.h
+++ b/drivers/hv/hyperv_vmbus.h
@@ -485,6 +485,10 @@ struct hv_context {
 
        void *synic_message_page[MAX_NUM_CPUS];
        void *synic_event_page[MAX_NUM_CPUS];
+       /*
+        * buffer to post messages to the host.
+        */
+       void *post_msg_page[MAX_NUM_CPUS];
 };
 
 extern struct hv_context hv_context;