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    SubjectRe: [RFC][PATCH] virtio balloon: kill tell-host-first logic
    On (Tue) 12 Apr 2011 [09:22:32], Dave Hansen wrote:
    > On Tue, 2011-04-12 at 11:13 +0530, Amit Shah wrote:
    > > Sure, the only contention was on the commit message, where you stated
    > > modern qemus set this... qemu doesn't, and it should. Care to do a
    > > patch for that?
    > If Rusty hasn't pushed the commit out anywhere, we can still amend the
    > commit. Otherwise, we're in a _bit_ of a pickle since you can't patch
    > git logs. :)

    I should've been clearer: care to do the qemu patch? :-)

    > Whatever is easiest for Rusty works for me.
    > How about this for a replacement log?
    > --
    > 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
    > feature, 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; we're under no obligation to do _anything_.
    > That's the state of affairs in current qemu:

    Actually this is just the bit number; it doesn't get set.


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