From: K. Y. Srinivasan <kys@microsoft.com>
Date: Fri, 29 Aug 2014 01:29:52 +0000 (-0700)
Subject: Drivers: hv: vmbus: Cleanup hv_post_message()
X-Git-Tag: v3.2.65~142
X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=f9149ce369d9aeef39194f2738b8e53ab73df406;p=pandora-kernel.git

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>
---

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