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Date: Sun, 10 Apr 2011 08:18:22 +0930 From: Rusty Russell <rusty@...tcorp.com.au> To: Dave Hansen <dave@...ux.vnet.ibm.com> Cc: "Michael S. Tsirkin" <mst@...hat.com>, virtualization@...ts.linux-foundation.org, linux-kernel@...r.kernel.org, Dave Hansen <dave@...ux.vnet.ibm.com> Subject: Re: [RFC][PATCH] virtio balloon: kill tell-host-first logic On Thu, 07 Apr 2011 10:43:25 -0700, Dave Hansen <dave@...ux.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@...ux.vnet.ibm.com> Thanks, applied! Rusty. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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