linux-kernel - RE: [patch] Staging: hv: Fix vmbus load hang caused by wrong data packing

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Message-ID: <1FB5E1D5CA062146B38059374562DF7212DF10DD@TK5EX14MBXC130.redmond.corp.microsoft.com>
Date:	Mon, 12 Oct 2009 17:03:42 +0000
From:	Haiyang Zhang <haiyangz@...rosoft.com>
To:	Greg KH <gregkh@...e.de>
CC:	Hank Janssen <hjanssen@...rosoft.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Tom Hanrahan <hanrahat@...rosoft.com>,
	"Hashir Abdi" <habdi@...rosoft.com>
Subject: RE: [patch] Staging: hv: Fix vmbus load hang caused by wrong data
 packing

>  	ChannelMessageCount
> -} __attribute__((packed));

Why the change here?  Isn't this doing the same thing?

And I'm guessing that not all of these structures are needing to be
packed, right?  Are they all shared across the HV boundry?

And is this fixing the problem that Hank and users have reported with
the current code?  Does this need to get into the 2.6.32 release?

thanks,

greg k-h
================================================
Hi Greg,

Based on our testing, the #pragma pack(push,1) can pack the data correctly for the HyperV to use, but __attribute__((packed)) couldn't do this right.

These data structures are moved by someone from the original file, ChannelMessages.h, which contains structures used for messaging to host.

Yes, it's fixing the problem that Hank and users have reported with the current code. And yes, 2.6.32 needs this fix.

Thanks,

- Haiyang

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