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From: Rusty Russell <rusty@rustcorp.com.au>
To: Dave Hansen <dave@linux.vnet.ibm.com>
Cc: "Michael S. Tsirkin" <mst@redhat.com>,
	virtualization@lists.linux-foundation.org,
	linux-kernel@vger.kernel.org,
	Dave Hansen <dave@linux.vnet.ibm.com>
Subject: Re: [RFC][PATCH] virtio balloon: kill tell-host-first logic
Date: Sun, 10 Apr 2011 08:18:22 +0930	[thread overview]
Message-ID: <87ei5bdosp.fsf@rustcorp.com.au> (raw)
In-Reply-To: <20110407174325.ED21C82B@kernel>

On Thu, 07 Apr 2011 10:43:25 -0700, Dave Hansen <dave@linux.vnet.ibm.com> wrote:
> 
> The virtio balloon driver has a VIRTIO_BALLOON_F_MUST_TELL_HOST
> feature bit.  Whenever the bit is set, we must always tell the
> host before we free pages back to the allocator.  Without this
> we might free a page (and have another user touch it) while the
> hypervisor is unprepared for it.
> 
> But, if the bit is _not_ set, we are under no obligation to
> reverse the order.  Furthermore, all modern qemus set this bit.
> So, the "tell second" code is completely unused and untestable.
> Quoting Anthony: "untested code is broken code".
> 
> This _also_ means that we don't have to preserve a pfn list
> after the pages are freed, which should let us get rid of some
> temporary storage (vb->pfns) eventually.
> 
> Signed-off-by: Dave Hansen <dave@linux.vnet.ibm.com>

Thanks, applied!

Rusty.

  reply	other threads:[~2011-04-10  0:42 UTC|newest]

Thread overview: 12+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2011-04-07 17:43 Dave Hansen
2011-04-09 22:48 ` Rusty Russell [this message]
2011-04-11 11:01 ` Michael S. Tsirkin
2011-04-11 22:11   ` Dave Hansen
2011-04-12  5:43     ` Amit Shah
2011-04-12 16:22       ` Dave Hansen
2011-04-12 16:43         ` Amit Shah
2011-04-14 20:28           ` Dave Hansen
2011-04-15 10:39             ` Amit Shah
2011-04-14 11:37         ` Rusty Russell
2011-04-14 20:30           ` Dave Hansen
2011-04-19  1:25             ` Rusty Russell

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