[PATCH 3.13 038/105] Drivers: hv: vmbus: Cleanup hv_post_message()

Kamal Mostafa
2014-10-27T19:03:22Z

From: "K. Y. Srinivasan" <kys@microsoft.com>

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>
Signed-off-by: Kamal Mostafa <kamal@canonical.com>
---
drivers/hv/hv.c | 27 +++++++++++++++------------
drivers/hv/hyperv_vmbus.h | 4 ++++
2 files changed, 19 insertions(+), 12 deletions(-)

diff --git a/drivers/hv/hv.c b/drivers/hv/hv.c
index f0c5e07..0e3c124 100644
--- 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 @@ 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 e055176..9fa0cab 100644
--- a/drivers/hv/hyperv_vmbus.h
+++ b/drivers/hv/hyperv_vmbus.h
@@ -510,6 +510,10 @@ struct hv_context {
* basis.
*/
struct tasklet_struct *event_dpc[NR_CPUS];
+ /*
+ * buffer to post messages to the host.
+ */
+ void *post_msg_page[NR_CPUS];
};

extern struct hv_context hv_context;
--
1.9.1