Commit b29ef354 authored by K. Y. Srinivasan's avatar K. Y. Srinivasan Committed by Greg Kroah-Hartman
Browse files

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: default avatarK. Y. Srinivasan <kys@microsoft.com>
Reported-by: default avatarSitsofe Wheeler <sitsofe@yahoo.com>
Cc: <stable@vger.kernel.org>
Tested-by: default avatarSitsofe Wheeler <sitsofe@yahoo.com>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent 98d731bb

drivers/hv/hv.c

+15 −12
Original line number Diff line number Diff line
@@ -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)

drivers/hv/hyperv_vmbus.h

+4 −0
Original line number Diff line number Diff line
@@ -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;

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