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From: Yuanhan Liu <yuanhan.liu@linux.intel.com>
To: "Michael S. Tsirkin" <mst@redhat.com>
Cc: "Marc-André Lureau" <marcandre.lureau@gmail.com>,
	QEMU <qemu-devel@nongnu.org>,
	"Ilya Maximets" <i.maximets@samsung.com>,
	jonshin@cisco.com, "Tetsuya Mukawa" <mukawa@igel.co.jp>,
	"Xie, Huawei" <huawei.xie@intel.com>
Subject: Re: [Qemu-devel] [PATCH 11/18] vhost-user: add shutdown support
Date: Sun, 1 May 2016 14:04:42 -0700	[thread overview]
Message-ID: <20160501210442.GK5641@yliu-dev.sh.intel.com> (raw)
In-Reply-To: <20160501134233-mutt-send-email-mst@redhat.com>

On Sun, May 01, 2016 at 02:37:19PM +0300, Michael S. Tsirkin wrote:
> On Fri, Apr 29, 2016 at 10:48:35AM -0700, Yuanhan Liu wrote:
> > > But, I
> > > would worry first about a backend that crashes that it may corrupt the
> > > VM memory too...
> > 
> > Not quite sure I follow this. But, backend just touches the virtio
> > related memory, so it will do no harm to the VM?
> 
> It crashed so apparently it's not behaving as designed -
> how can we be sure it does not harm the VM?

Hi Michael,

What I know so far, a crash might could corrupt the virtio memory in two
ways:

- vring_used_elem might be in stale state when we are in the middle of
  updating used vring. Say, we might have updated the "id" field, but
  leaving "len" untouched.

- vring desc buff might also be in stale state, when we are copying
  data into it.

However, the two issues will not be real issue, as used->idx is not
updated in both case. Thefore, those corrupted memory will not be
processed by guest. So, no harm I'd say. Or, am I missing anything?

BTW, Michael, what's your thoughts on the whole reconnect stuff?

	--yliu

  reply	other threads:[~2016-05-01 21:02 UTC|newest]

Thread overview: 42+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2016-04-01 11:16 [Qemu-devel] [PATCH 00/18] RFCv2: vhost-user: shutdown and reconnection marcandre.lureau
2016-04-01 11:16 ` [Qemu-devel] [PATCH 01/18] tests: append i386 tests marcandre.lureau
2016-04-01 20:30   ` [Qemu-devel] [PATCH 01/18 for-2.6] " Eric Blake
2016-04-01 11:16 ` [Qemu-devel] [PATCH 02/18] char: lower reconnect error to trace event marcandre.lureau
2016-04-01 11:16 ` [Qemu-devel] [PATCH 03/18] char: use a trace for when the char is waiting marcandre.lureau
2016-04-01 11:16 ` [Qemu-devel] [PATCH 04/18] char: add wait support for reconnect marcandre.lureau
2016-04-28  4:33   ` Yuanhan Liu
2016-04-01 11:16 ` [Qemu-devel] [PATCH 05/18] vhost-user: check reconnect comes with wait marcandre.lureau
2016-04-01 11:16 ` [Qemu-devel] [PATCH 06/18] vhost-user: add ability to know vhost-user backend disconnection marcandre.lureau
2016-04-01 11:16 ` [Qemu-devel] [PATCH 07/18] vhost: add vhost_dev stop callback marcandre.lureau
2016-04-01 11:16 ` [Qemu-devel] [PATCH 08/18] vhost-user: add vhost_user to hold the chr marcandre.lureau
2016-04-01 11:16 ` [Qemu-devel] [PATCH 09/18] qemu-char: add qemu_chr_disconnect to close a fd accepted by listen fd marcandre.lureau
2016-04-01 11:16 ` [Qemu-devel] [PATCH 10/18] vhost-user: add slave-fd support marcandre.lureau
2016-04-01 20:33   ` Eric Blake
2016-04-01 11:16 ` [Qemu-devel] [PATCH 11/18] vhost-user: add shutdown support marcandre.lureau
2016-04-13  2:49   ` Yuanhan Liu
2016-04-13  9:51     ` Marc-André Lureau
2016-04-13 17:32       ` Yuanhan Liu
2016-04-13 21:43         ` Marc-André Lureau
2016-04-13 21:57           ` Yuanhan Liu
2016-04-28  5:23   ` Yuanhan Liu
2016-04-29 10:40     ` Marc-André Lureau
2016-04-29 17:48       ` Yuanhan Liu
2016-05-01 11:37         ` Michael S. Tsirkin
2016-05-01 21:04           ` Yuanhan Liu [this message]
2016-05-02 10:45             ` Michael S. Tsirkin
2016-05-02 11:29               ` Marc-André Lureau
2016-05-02 12:04                 ` Michael S. Tsirkin
2016-05-02 17:50                   ` Yuanhan Liu
2016-05-04 13:16                   ` Marc-André Lureau
2016-05-04 19:13                     ` Michael S. Tsirkin
2016-05-05  3:44                       ` Yuanhan Liu
2016-05-05 13:42                         ` Michael S. Tsirkin
2016-05-02 17:37               ` Yuanhan Liu
2016-04-01 11:16 ` [Qemu-devel] [PATCH 12/18] vhost-user: disconnect on start failure marcandre.lureau
2016-04-01 11:16 ` [Qemu-devel] [PATCH 13/18] vhost-net: do not crash if backend is not present marcandre.lureau
2016-04-01 11:16 ` [Qemu-devel] [PATCH 14/18] vhost-net: save & restore vhost-user acked features marcandre.lureau
2016-04-01 11:16 ` [Qemu-devel] [PATCH 15/18] vhost-net: save & restore vring enable state marcandre.lureau
2016-04-01 11:16 ` [Qemu-devel] [PATCH 16/18] test: vubr check " marcandre.lureau
2016-04-01 11:16 ` [Qemu-devel] [PATCH 17/18] test: start vhost-user reconnect test marcandre.lureau
2016-04-01 11:16 ` [Qemu-devel] [PATCH 18/18] test: add shutdown support vubr test marcandre.lureau
2016-04-13  2:52   ` Yuanhan Liu

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