From: Jan Beulich <jbeulich@suse.com>
To: Chao Gao <chao.gao@intel.com>
Cc: xen-devel@lists.xenproject.org
Subject: Re: [Xen-devel] Reset pass-thru devices in a VM
Date: Fri, 9 Aug 2019 15:23:59 +0200 [thread overview]
Message-ID: <b3887a04-a7a0-61ee-2037-36322c388d6b@suse.com> (raw)
In-Reply-To: <20190809132412.GA12877@gao-cwp>
On 09.08.2019 15:24, Chao Gao wrote:
> On Fri, Aug 09, 2019 at 10:49:32AM +0200, Jan Beulich wrote:
>> On 09.08.2019 10:38, Chao Gao wrote:
>>> 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?
>>
>> Wouldn't a such emulated guest initiated reset affect other devices
>> (likely not under control of this guest) as well?
>
> No. Linux kernel guarantees that reset to a device won't affect
> other devices. Otherwise, such device cannot be reset and no
> 'reset' attribute will be created under device's sysfs.
> Specfically, the invocation of pci_dev_reset_slot_function() and
> pci_parent_bus_reset() in pci_probe_reset_function() will check whether
> the device (function) is the only one under the slot or bus
> respectively. In pci_create_capabilities_sysfs(), 'reset' attribute is
> created only if dev->reset_fn is not zero.
Ah, good. But then the opposite question arises: How would your
proposed change help if the device shares a bus with others?
Jan
_______________________________________________
Xen-devel mailing list
Xen-devel@lists.xenproject.org
https://lists.xenproject.org/mailman/listinfo/xen-devel
next prev parent reply other threads:[~2019-08-09 13:24 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 [this message]
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
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=b3887a04-a7a0-61ee-2037-36322c388d6b@suse.com \
--to=jbeulich@suse.com \
--cc=chao.gao@intel.com \
--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).