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Re: [Qemu-devel] [PATCH] vhost-user: Slave crashes as Master unmaps vrin
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From: |
Michael S. Tsirkin |
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Subject: |
Re: [Qemu-devel] [PATCH] vhost-user: Slave crashes as Master unmaps vrings during guest reboot |
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Date: |
Sun, 17 Jan 2016 13:23:42 +0200 |
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)