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From: "Dr. David Alan Gilbert" <dgilbert@redhat.com>
To: "Michael S. Tsirkin" <mst@redhat.com>
Cc: Alexander Duyck <alexander.duyck@gmail.com>,
	Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>,
	Alexander Duyck <aduyck@mirantis.com>,
	kvm@vger.kernel.org,
	"linux-pci@vger.kernel.org" <linux-pci@vger.kernel.org>,
	x86@kernel.org,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	qemu-devel@nongnu.org, Lan Tianyu <tianyu.lan@intel.com>,
	Yang Zhang <yang.zhang.wz@gmail.com>,
	Alexander Graf <agraf@suse.de>,
	Alex Williamson <alex.williamson@redhat.com>
Subject: Re: [RFC PATCH 0/3] x86: Add support for guest DMA dirty page tracking
Date: Tue, 5 Jan 2016 10:01:04 +0000	[thread overview]
Message-ID: <20160105100104.GA2439@work-vm> (raw)
In-Reply-To: <20160105113317-mutt-send-email-mst@redhat.com>

* Michael S. Tsirkin (mst@redhat.com) wrote:
> On Mon, Jan 04, 2016 at 07:11:25PM -0800, Alexander Duyck wrote:
> > >> The two mechanisms referenced above would likely require coordination with
> > >> QEMU and as such are open to discussion.  I haven't attempted to address
> > >> them as I am not sure there is a consensus as of yet.  My personal
> > >> preference would be to add a vendor-specific configuration block to the
> > >> emulated pci-bridge interfaces created by QEMU that would allow us to
> > >> essentially extend shpc to support guest live migration with pass-through
> > >> devices.
> > >
> > > shpc?
> > 
> > That is kind of what I was thinking.  We basically need some mechanism
> > to allow for the host to ask the device to quiesce.  It has been
> > proposed to possibly even look at something like an ACPI interface
> > since I know ACPI is used by QEMU to manage hot-plug in the standard
> > case.
> > 
> > - Alex
> 
> 
> Start by using hot-unplug for this!
> 
> Really use your patch guest side, and write host side
> to allow starting migration with the device, but
> defer completing it.
> 
> So
> 
> 1.- host tells guest to start tracking memory writes
> 2.- guest acks
> 3.- migration starts
> 4.- most memory is migrated
> 5.- host tells guest to eject device
> 6.- guest acks
> 7.- stop vm and migrate rest of state
> 
> 
> It will already be a win since hot unplug after migration starts and
> most memory has been migrated is better than hot unplug before migration
> starts.
> 
> Then measure downtime and profile. Then we can look at ways
> to quiesce device faster which really means step 5 is replaced
> with "host tells guest to quiesce device and dirty (or just unmap!)
> all memory mapped for write by device".


Doing a hot-unplug is going to upset the guests network stacks view
of the world; that's something we don't want to change.

Dave

> 
> -- 
> MST
--
Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK

  reply	other threads:[~2016-01-05 10:01 UTC|newest]

Thread overview: 35+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2015-12-13 21:28 [RFC PATCH 0/3] x86: Add support for guest DMA dirty page tracking Alexander Duyck
2015-12-13 21:28 ` [RFC PATCH 1/3] swiotlb: Fold static unmap and sync calls into calling functions Alexander Duyck
2015-12-13 21:28 ` [RFC PATCH 2/3] xen/swiotlb: " Alexander Duyck
2015-12-13 21:28 ` [RFC PATCH 3/3] x86: Create dma_mark_dirty to dirty pages used for DMA by VM guest Alexander Duyck
2015-12-14 14:00   ` Michael S. Tsirkin
2015-12-14 16:34     ` Alexander Duyck
2015-12-14 17:20       ` Michael S. Tsirkin
2015-12-14 17:59         ` Alexander Duyck
2015-12-14 20:52           ` Michael S. Tsirkin
2015-12-14 22:32             ` Alexander Duyck
2015-12-14  2:27 ` [RFC PATCH 0/3] x86: Add support for guest DMA dirty page tracking Yang Zhang
2015-12-14  4:54   ` Alexander Duyck
2015-12-14  5:22     ` Yang Zhang
2015-12-14  5:46       ` Alexander Duyck
2015-12-14  7:20         ` Yang Zhang
2015-12-14 14:02           ` Michael S. Tsirkin
     [not found] ` <20160104204104.GB17427@char.us.oracle.com>
2016-01-05  3:11   ` Alexander Duyck
2016-01-05  9:40     ` Michael S. Tsirkin
2016-01-05 10:01       ` Dr. David Alan Gilbert [this message]
2016-01-05 10:35         ` Michael S. Tsirkin
2016-01-05 10:45           ` Dr. David Alan Gilbert
2016-01-05 10:59             ` Michael S. Tsirkin
2016-01-05 11:03               ` Dr. David Alan Gilbert
2016-01-05 11:11                 ` Michael S. Tsirkin
2016-01-05 11:06               ` Michael S. Tsirkin
2016-01-05 11:05             ` Michael S. Tsirkin
2016-01-05 12:43               ` Dr. David Alan Gilbert
2016-01-05 13:16                 ` Michael S. Tsirkin
2016-01-05 16:18       ` Alexander Duyck
2016-06-06  9:18         ` Re: [Qemu-devel] " Zhou Jie
2016-06-06 16:04           ` Alex Duyck
2016-06-09 10:14             ` Zhou Jie
2016-06-09 15:39               ` Alexander Duyck
2016-06-12  3:03                 ` Zhou Jie
2016-06-13  1:28                   ` Alexander Duyck

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