From: Chao Gao <chao.gao@intel.com>
To: "Pasi Kärkkäinen" <pasik@iki.fi>
Cc: xen-devel@lists.xenproject.org
Subject: Re: [Xen-devel] Reset pass-thru devices in a VM
Date: Tue, 27 Aug 2019 12:40:05 +0800 [thread overview]
Message-ID: <20190827044004.GA28246@gao-cwp> (raw)
In-Reply-To: <20190826211728.GF2840@reaktio.net>
On Tue, Aug 27, 2019 at 12:17:28AM +0300, Pasi Kärkkäinen wrote:
>Hi Chao,
>
>On Fri, Aug 09, 2019 at 04:38:33PM +0800, Chao Gao wrote:
>> Hi everyone,
>>
>> I have a device which only supports secondary bus reset. After being
>> assigned to a VM, it would be placed under host bridge. For devices
>> under host bridge, secondary bus reset is not applicable. Thus, a VM
>> has no way to reset this device.
>>
>> This device's usage would be limited without PCI reset (for example, its
>> driver cannot re-initialize the device properly without PCI reset, which
>> means in VM device won't be usable after unloading the driver), it would
>> be much better if there is a way available to VMs to reset the device.
>>
>> In my mind, a straightfoward solution is to create a virtual bridge
>> for a VM and place the pass-thru device under a virtual bridge. But it
>> isn't supported in Xen (KVM/QEMU supports) and enabling it looks need
>> a lot of efforts. Alternatively, emulating FLR (Function Level Reset)
>> capability for this device might be a feasible way and only needs
>> relatively few changes. I am planning to enable an opt-in feature
>> (like 'permissive') to allow qemu to expose FLR capability to guest for
>> pass-thru devices as long as this device is resetable on dom0 (i.e. the
>> device has 'reset' attribute under its sysfs). And when guest initiates
>> an FLR, qemu just echo 1 to the 'reset' attribute on dom0.
>>
>> Do you think emulating FLR capability is doable?
>>
>
>I wonder if these patches from another thread help with your reset issue:
>
>https://lists.xen.org/archives/html/xen-devel/2019-08/msg02304.html
Thanks for your attention.
The link you provides seems about how host resets a device. Emulating FLR
capability is to expose FLR capability to guest such that guest can
reset assigned devices. Definitely, qemu would intercept guest's
initiating an FLR and redirect it into a device reset on host.
Thanks
Chao
_______________________________________________
Xen-devel mailing list
Xen-devel@lists.xenproject.org
https://lists.xenproject.org/mailman/listinfo/xen-devel
prev parent reply other threads:[~2019-08-27 4:36 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-08-09 8:38 [Xen-devel] Reset pass-thru devices in a VM Chao Gao
2019-08-09 8:49 ` Jan Beulich
2019-08-09 13:24 ` Chao Gao
2019-08-09 13:23 ` Jan Beulich
2019-08-09 14:13 ` Chao Gao
2019-08-09 12:42 ` Roger Pau Monné
2019-08-09 13:57 ` Chao Gao
2019-08-26 21:17 ` Pasi Kärkkäinen
2019-08-27 4:40 ` Chao Gao [this message]
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20190827044004.GA28246@gao-cwp \
--to=chao.gao@intel.com \
--cc=pasik@iki.fi \
--cc=xen-devel@lists.xenproject.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).