From: "shesha Sreenivasamurthy (shesha)" <shesha@cisco.com>
To: "Michael S. Tsirkin" <mst@redhat.com>
Cc: "qemu-devel@nongnu.org" <qemu-devel@nongnu.org>
Subject: Re: [Qemu-devel] [PATCH] vhost-user: Slave crashes as Master unmaps vrings during guest reboot
Date: Mon, 18 Jan 2016 21:40:52 +0000 [thread overview]
Message-ID: <D2C29BA3.28FBD%shesha@cisco.com> (raw)
In-Reply-To: <20160117132238-mutt-send-email-mst@redhat.com>
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Got it. Thanks, I missed that line while reading the spec. Is docs/specs/vhost-user.txt the official spec ?
--
- Thanks
char * (*shesha) (uint64_t cache, uint8_t F00D)
{ return 0x0000C0DE; }
From: "Michael S. Tsirkin" <mst@redhat.com<mailto:mst@redhat.com>>
Date: Sunday, January 17, 2016 at 3:23 AM
To: Cisco Employee <shesha@cisco.com<mailto:shesha@cisco.com>>
Cc: "qemu-devel@nongnu.org<mailto:qemu-devel@nongnu.org>" <qemu-devel@nongnu.org<mailto:qemu-devel@nongnu.org>>
Subject: Re: [PATCH] vhost-user: Slave crashes as Master unmaps vrings during guest reboot
On Fri, Jan 15, 2016 at 12:12:43PM -0800, Shesha Sreenivasamurthy wrote:
Problem:
--------
If a guest has vhost-user enabled, then on reboot vhost_virtqueue_stop
is invoked. This unmaps vring memory mappings. However, it will not give
any indication to the underlying DPDK slave application about it.
Therefore, a pollmode DPDK driver tries to read the ring to check for
packets and segfaults.
The spec currently says:
Client must start ring upon receiving a kick (that is, detecting that file
descriptor is readable) on the descriptor specified by
VHOST_USER_SET_VRING_KICK, and stop ring upon receiving
VHOST_USER_GET_VRING_BASE.
Why isn't this sufficient?
Solution:
----------
VHOST_USER_RESET_OWNER API is issued by QEMU so that DPDK slave
application is informed that mappings will be soon gone so that
it can take necessary steps.
Shesha Sreenivasamurthy (1):
vhost-user: Slave crashes as Master unmaps vrings during guest reboot
hw/virtio/vhost.c | 5 +++++
1 file changed, 5 insertions(+)
--
1.9.5 (Apple Git-50.3)
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next prev parent reply other threads:[~2016-01-18 21:41 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-01-15 20:12 [Qemu-devel] [PATCH] vhost-user: Slave crashes as Master unmaps vrings during guest reboot Shesha Sreenivasamurthy
2016-01-15 20:12 ` Shesha Sreenivasamurthy
2016-01-17 11:30 ` Michael S. Tsirkin
2016-01-17 11:23 ` Michael S. Tsirkin
2016-01-18 21:40 ` shesha Sreenivasamurthy (shesha) [this message]
-- strict thread matches above, loose matches on Subject: below --
2016-01-15 20:23 Shesha Sreenivasamurthy
2016-01-15 20:23 ` Shesha Sreenivasamurthy
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