From: Jason Wang <jasowang@redhat.com>
To: "Michael S. Tsirkin" <mst@redhat.com>
Cc: kvm@vger.kernel.org, virtualization@lists.linux-foundation.org,
netdev@vger.kernel.org, linux-kernel@vger.kernel.org,
davem@davemloft.net
Subject: Re: [RFC PATCH V3 0/5] Hi:
Date: Fri, 11 Jan 2019 16:59:13 +0800 [thread overview]
Message-ID: <303660e9-5ad4-975d-535d-bd158d99884e@redhat.com> (raw)
In-Reply-To: <682d520e-00e3-cdaa-d51e-23524ae48854@redhat.com>
On 2019/1/8 下午6:12, Jason Wang wrote:
>
> On 2019/1/7 下午10:47, Michael S. Tsirkin wrote:
>> On Mon, Jan 07, 2019 at 02:58:08PM +0800, Jason Wang wrote:
>>> On 2019/1/5 上午5:41, Michael S. Tsirkin wrote:
>>>> On Sat, Dec 29, 2018 at 08:46:51PM +0800, Jason Wang wrote:
>>>>> This series tries to access virtqueue metadata through kernel virtual
>>>>> address instead of copy_user() friends since they had too much
>>>>> overheads like checks, spec barriers or even hardware feature
>>>>> toggling.
>>>> I think it's a reasonable approach.
>>>> However I need to look at whether and which mmu notifiers are
>>>> invoked before
>>>> writeback. Do you know?
>>>
>>> I don't know but just looking at the MMU notifier ops definition,
>>> there's no
>>> such callback if my understanding is correct.
>>>
>>> Thanks
>> In that case how are you making sure used ring updates are written back?
>> If they aren't guest will crash ...
>
>
> I think this is the writeback issue you mentioned early. I don't do a
> followup on the pointer but it looks to me some work is ongoing to fix
> the issue.
>
> I can investigate it more, but it's not something new, consider the
> case of VFIO.
>
> Thanks
Ok, after some investigation. The GUP + dirty pages issue is not easy to
be fixed so it may still take a while.
An idea is switch back to copy_user() friends if we find the metadata
page is not anonymous.
Does this sound good to you?
Thanks
prev parent reply other threads:[~2019-01-11 8:59 UTC|newest]
Thread overview: 33+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-12-29 12:46 [RFC PATCH V3 0/5] Hi: Jason Wang
2018-12-29 12:46 ` [RFC PATCH V3 1/5] vhost: generalize adding used elem Jason Wang
2019-01-04 21:29 ` Michael S. Tsirkin
2019-01-05 0:33 ` Sean Christopherson
2019-01-07 7:00 ` Jason Wang
2019-01-07 14:50 ` Michael S. Tsirkin
2018-12-29 12:46 ` [RFC PATCH V3 2/5] vhost: fine grain userspace memory accessors Jason Wang
2018-12-29 12:46 ` [RFC PATCH V3 3/5] vhost: rename vq_iotlb_prefetch() to vq_meta_prefetch() Jason Wang
2018-12-29 12:46 ` [RFC PATCH V3 4/5] vhost: introduce helpers to get the size of metadata area Jason Wang
2018-12-29 12:46 ` [RFC PATCH V3 5/5] vhost: access vq metadata through kernel virtual address Jason Wang
2019-01-04 21:34 ` Michael S. Tsirkin
2019-01-07 8:40 ` Jason Wang
2019-01-02 20:47 ` [RFC PATCH V3 0/5] Hi: Michael S. Tsirkin
2019-01-07 2:19 ` Jason Wang
2019-01-07 3:28 ` Michael S. Tsirkin
2019-01-07 3:53 ` Jason Wang
2019-01-07 4:17 ` Michael S. Tsirkin
2019-01-07 6:50 ` Jason Wang
2019-01-07 14:37 ` Michael S. Tsirkin
2019-01-08 10:01 ` Jason Wang
2019-01-07 7:15 ` Dan Williams
2019-01-07 14:11 ` Michael S. Tsirkin
2019-01-07 21:39 ` Dan Williams
2019-01-07 22:25 ` Michael S. Tsirkin
2019-01-07 22:44 ` Dan Williams
2019-01-09 4:31 ` __get_user slower than get_user (was Re: [RFC PATCH V3 0/5] Hi:) Michael S. Tsirkin
2019-01-09 5:19 ` Linus Torvalds
2019-01-08 11:42 ` [RFC PATCH V3 0/5] Hi: Jason Wang
2019-01-04 21:41 ` Michael S. Tsirkin
2019-01-07 6:58 ` Jason Wang
2019-01-07 14:47 ` Michael S. Tsirkin
2019-01-08 10:12 ` Jason Wang
2019-01-11 8:59 ` Jason Wang [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=303660e9-5ad4-975d-535d-bd158d99884e@redhat.com \
--to=jasowang@redhat.com \
--cc=davem@davemloft.net \
--cc=kvm@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=mst@redhat.com \
--cc=netdev@vger.kernel.org \
--cc=virtualization@lists.linux-foundation.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).