From: Peter Xu <peterx@redhat.com>
To: "Michael S. Tsirkin" <mst@redhat.com>
Cc: Wei Wang <wei.w.wang@intel.com>,
qemu-devel@nongnu.org, virtio-dev@lists.oasis-open.org,
quintela@redhat.com, dgilbert@redhat.com,
yang.zhang.wz@gmail.com, quan.xu0@gmail.com,
liliang.opensource@gmail.com, pbonzini@redhat.com,
nilal@redhat.com
Subject: Re: [Qemu-devel] [PATCH v7 4/5] virtio-balloon: VIRTIO_BALLOON_F_FREE_PAGE_HINT
Date: Fri, 8 Jun 2018 10:34:25 +0800 [thread overview]
Message-ID: <20180608023425.GT750@xz-mi> (raw)
In-Reply-To: <20180608045316-mutt-send-email-mst@kernel.org>
On Fri, Jun 08, 2018 at 04:58:21AM +0300, Michael S. Tsirkin wrote:
> On Fri, Jun 08, 2018 at 09:37:23AM +0800, Peter Xu wrote:
> > > > Asked since I see this in virtio spec (v1.0, though I guess it won't
> > > > change) in chapter "2.2.1 Driver Requirements: Feature Bits":
> > > >
> > > > "The driver MUST NOT accept a feature which the device did not offer"
> > > >
> > > > Then I'm curious what would happen if:
> > > >
> > > > - a emulator (not QEMU) only offered F_FREE_PAGE_HINT, not F_POISON
> > > > - a guest that enabled PAGE_POISON
> > > >
> > > > Then how the driver could tell the host that PAGE_POISON is enabled
> > > > considering that guest should never set that feature bit if the
> > > > emulation code didn't provide it?
>
> It wouldn't. It just has to deal with the fact that host can discard
> writes to hinted pages. Right now driver deals with it simply by
> disabling F_FREE_PAGE_HINT.
Ah I see. Thanks Michael.
Then it seems to me that it's more important to implement the F_POISON
along with where it is declared since otherwise it'll be a real broken
(device declares F_POISON, guest assumes it can handle the POISON so
guest will enable FREE_PAGE_HINT, however the device can't really
handle that).
Or, if the guest driver is capable to drop F_FREE_PAGE_HINT when
F_POISON is not declared, we can safely split the two features into
two patches in QEMU too.
Regards,
--
Peter Xu
next prev parent reply other threads:[~2018-06-08 2:34 UTC|newest]
Thread overview: 93+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-04-24 6:13 [Qemu-devel] [PATCH v7 0/5] virtio-balloon: free page hint reporting support Wei Wang
2018-04-24 6:13 ` [virtio-dev] " Wei Wang
2018-04-24 6:13 ` [Qemu-devel] [PATCH v7 1/5] bitmap: bitmap_count_one_with_offset Wei Wang
2018-04-24 6:13 ` [virtio-dev] " Wei Wang
2018-04-24 6:13 ` [Qemu-devel] [PATCH v7 2/5] migration: use bitmap_mutex in migration_bitmap_clear_dirty Wei Wang
2018-04-24 6:13 ` [virtio-dev] " Wei Wang
2018-06-01 3:37 ` [Qemu-devel] " Peter Xu
2018-04-24 6:13 ` [Qemu-devel] [PATCH v7 3/5] migration: API to clear bits of guest free pages from the dirty bitmap Wei Wang
2018-04-24 6:13 ` [virtio-dev] " Wei Wang
2018-06-01 4:00 ` [Qemu-devel] " Peter Xu
2018-06-01 7:36 ` Wei Wang
2018-06-01 7:36 ` [virtio-dev] " Wei Wang
2018-06-01 10:06 ` Peter Xu
2018-06-01 12:32 ` Wei Wang
2018-06-01 12:32 ` [virtio-dev] " Wei Wang
2018-06-04 2:49 ` Peter Xu
2018-06-04 7:43 ` Wei Wang
2018-06-04 7:43 ` [virtio-dev] " Wei Wang
2018-04-24 6:13 ` [Qemu-devel] [PATCH v7 4/5] virtio-balloon: VIRTIO_BALLOON_F_FREE_PAGE_HINT Wei Wang
2018-04-24 6:13 ` [virtio-dev] " Wei Wang
2018-05-29 15:24 ` [Qemu-devel] " Michael S. Tsirkin
2018-05-29 15:24 ` [virtio-dev] " Michael S. Tsirkin
2018-05-30 9:12 ` [Qemu-devel] " Wei Wang
2018-05-30 9:12 ` [virtio-dev] " Wei Wang
2018-05-30 12:47 ` [Qemu-devel] " Michael S. Tsirkin
2018-05-30 12:47 ` [virtio-dev] " Michael S. Tsirkin
2018-05-31 2:27 ` [Qemu-devel] " Wei Wang
2018-05-31 2:27 ` [virtio-dev] " Wei Wang
2018-05-31 17:42 ` [Qemu-devel] " Michael S. Tsirkin
2018-05-31 17:42 ` [virtio-dev] " Michael S. Tsirkin
2018-06-01 3:18 ` [Qemu-devel] " Wei Wang
2018-06-01 3:18 ` [virtio-dev] " Wei Wang
2018-06-04 8:04 ` [Qemu-devel] " Wei Wang
2018-06-04 8:04 ` [virtio-dev] " Wei Wang
2018-06-05 6:58 ` [Qemu-devel] " Peter Xu
2018-06-05 13:22 ` Wei Wang
2018-06-05 13:22 ` [virtio-dev] " Wei Wang
2018-06-06 5:42 ` [Qemu-devel] " Peter Xu
2018-06-06 10:04 ` Wei Wang
2018-06-06 10:04 ` [virtio-dev] " Wei Wang
2018-06-06 11:02 ` [Qemu-devel] " Peter Xu
2018-06-07 5:24 ` Wei Wang
2018-06-07 5:24 ` [virtio-dev] " Wei Wang
2018-06-07 6:32 ` [Qemu-devel] " Peter Xu
2018-06-07 11:59 ` Wei Wang
2018-06-07 11:59 ` [virtio-dev] " Wei Wang
2018-06-08 2:17 ` [Qemu-devel] " Peter Xu
2018-06-08 7:14 ` Wei Wang
2018-06-08 7:14 ` [virtio-dev] " Wei Wang
2018-06-08 7:31 ` [Qemu-devel] " Wei Wang
2018-06-08 7:31 ` [virtio-dev] " Wei Wang
2018-06-06 6:43 ` [Qemu-devel] " Peter Xu
2018-06-06 10:11 ` Wei Wang
2018-06-06 10:11 ` [virtio-dev] " Wei Wang
2018-06-07 3:17 ` Peter Xu
2018-06-07 5:29 ` Wei Wang
2018-06-07 5:29 ` [virtio-dev] " Wei Wang
2018-06-07 6:58 ` Peter Xu
2018-06-07 12:01 ` Wei Wang
2018-06-07 12:01 ` [virtio-dev] " Wei Wang
2018-06-08 1:37 ` Peter Xu
2018-06-08 1:58 ` Peter Xu
2018-06-08 1:58 ` Michael S. Tsirkin
2018-06-08 1:58 ` [virtio-dev] " Michael S. Tsirkin
2018-06-08 2:34 ` Peter Xu [this message]
2018-06-08 2:49 ` Michael S. Tsirkin
2018-06-08 2:49 ` [virtio-dev] " Michael S. Tsirkin
2018-06-08 3:34 ` Peter Xu
2018-04-24 6:13 ` [Qemu-devel] [PATCH v7 5/5] migration: use the free page hint feature from balloon Wei Wang
2018-04-24 6:13 ` [virtio-dev] " Wei Wang
2018-04-24 6:42 ` [Qemu-devel] [PATCH v7 0/5] virtio-balloon: free page hint reporting support Wei Wang
2018-04-24 6:42 ` [virtio-dev] " Wei Wang
2018-05-14 1:22 ` [Qemu-devel] " Wei Wang
2018-05-14 1:22 ` [virtio-dev] " Wei Wang
2018-05-29 15:00 ` [Qemu-devel] " Hailiang Zhang
2018-05-29 15:24 ` Michael S. Tsirkin
2018-05-29 15:24 ` [virtio-dev] " Michael S. Tsirkin
2018-06-01 4:58 ` Peter Xu
2018-06-01 5:07 ` Peter Xu
2018-06-01 7:29 ` Wei Wang
2018-06-01 7:29 ` [virtio-dev] " Wei Wang
2018-06-01 10:02 ` Peter Xu
2018-06-01 12:31 ` Wei Wang
2018-06-01 12:31 ` [virtio-dev] " Wei Wang
2018-06-01 7:21 ` Wei Wang
2018-06-01 7:21 ` [virtio-dev] " Wei Wang
2018-06-01 10:40 ` Peter Xu
2018-06-01 15:33 ` Dr. David Alan Gilbert
2018-06-05 6:42 ` Peter Xu
2018-06-05 14:40 ` Michael S. Tsirkin
2018-06-05 14:40 ` [virtio-dev] " Michael S. Tsirkin
2018-06-05 14:39 ` Michael S. Tsirkin
2018-06-05 14:39 ` [virtio-dev] " Michael S. Tsirkin
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