From: Adam Litke <agl@us.ibm.com>
To: Jamie Lokier <jamie@shareable.org>
Cc: Anthony Liguori <aliguori@us.ibm.com>,
qemu-devel@nongnu.org, Avi Kivity <avi@redhat.com>
Subject: Re: [Qemu-devel] [RFC] virtio: Report new guest memory statistics pertinent to memory ballooning (V2)
Date: Mon, 09 Nov 2009 13:16:14 -0600 [thread overview]
Message-ID: <1257794174.2835.22.camel@aglitke> (raw)
In-Reply-To: <20091109190001.GA3808@shareable.org>
On Mon, 2009-11-09 at 19:00 +0000, Jamie Lokier wrote:
> Adam Litke wrote:
> > + s->stats.pswapin = has_feature(dev, VIRTIO_BALLOON_F_RPT_SWAP_OUT) ?
> > + dev->stats.pswapin : -1;
>
> (etc.)
>
> Why not simply have the guest fill in the unused fields with -1, and
> say that's how "no meaningful value" is represented in the ABI?
>
> All guests have to know about all those fields anyway, for the
> structure layout. Is there any benefit to specifying feature bits in
> advance over simply storing -1 there?
This holds true for fields that exist but might not be supported by a
guest, but what about the case where we add a new field? In that case,
qemu and the guest may disagree on the structure layout.
--
Thanks,
Adam
next prev parent reply other threads:[~2009-11-09 19:16 UTC|newest]
Thread overview: 23+ messages / expand[flat|nested] mbox.gz Atom feed top
2009-11-09 16:07 [Qemu-devel] [RFC] virtio: Report new guest memory statistics pertinent to memory ballooning (V2) Adam Litke
2009-11-09 16:32 ` [Qemu-devel] virtio: Add memory statistics reporting to the balloon driver Adam Litke
2009-11-10 2:42 ` [Qemu-devel] " Rusty Russell
2009-11-10 14:36 ` Anthony Liguori
2009-11-10 14:43 ` Avi Kivity
2009-11-10 14:58 ` Anthony Liguori
2009-11-11 9:24 ` Jamie Lokier
2009-11-11 10:12 ` Daniel P. Berrange
2009-11-11 13:26 ` Adam Litke
2009-11-11 15:00 ` Avi Kivity
2009-11-10 23:59 ` Rusty Russell
2009-11-10 21:52 ` Anthony Liguori
2009-11-11 0:02 ` Rusty Russell
2009-11-11 0:07 ` Anthony Liguori
2009-11-11 2:43 ` Rusty Russell
2009-11-11 15:08 ` Adam Litke
2009-11-12 2:29 ` Rusty Russell
2009-11-09 19:00 ` [Qemu-devel] [RFC] virtio: Report new guest memory statistics pertinent to memory ballooning (V2) Jamie Lokier
2009-11-09 19:16 ` Adam Litke [this message]
2009-11-09 21:15 ` Anthony Liguori
2009-11-10 13:23 ` Jamie Lokier
2009-11-09 19:01 ` Jamie Lokier
2009-11-09 19:23 ` Adam Litke
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