From: "Michael S. Tsirkin" <mst@redhat.com>
To: Peter Xu <peterx@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 04:58:21 +0300 [thread overview]
Message-ID: <20180608045316-mutt-send-email-mst@kernel.org> (raw)
In-Reply-To: <20180608013723.GQ750@xz-mi>
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.
--
MST
WARNING: multiple messages have this Message-ID (diff)
From: "Michael S. Tsirkin" <mst@redhat.com>
To: Peter Xu <peterx@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: [virtio-dev] Re: [Qemu-devel] [PATCH v7 4/5] virtio-balloon: VIRTIO_BALLOON_F_FREE_PAGE_HINT
Date: Fri, 8 Jun 2018 04:58:21 +0300 [thread overview]
Message-ID: <20180608045316-mutt-send-email-mst@kernel.org> (raw)
In-Reply-To: <20180608013723.GQ750@xz-mi>
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.
--
MST
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next prev parent reply other threads:[~2018-06-08 1:58 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 [this message]
2018-06-08 1:58 ` [virtio-dev] " Michael S. Tsirkin
2018-06-08 2:34 ` Peter Xu
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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