All of lore.kernel.org
 help / color / mirror / Atom feed
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

      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 an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.