From: "Michael S. Tsirkin" <mst@redhat.com>
To: Jason Wang <jasowang@redhat.com>
Cc: kvm@vger.kernel.org, virtualization@lists.linux-foundation.org,
netdev@vger.kernel.org, linux-kernel@vger.kernel.org,
Jintack Lim <jintack@cs.columbia.edu>
Subject: Re: [PATCH net V2 4/4] vhost: log dirty page correctly
Date: Fri, 14 Dec 2018 08:20:40 -0500 [thread overview]
Message-ID: <20181214081821-mutt-send-email-mst@kernel.org> (raw)
In-Reply-To: <519ee6f7-06fc-ad49-03da-c096aeb24ced@redhat.com>
On Fri, Dec 14, 2018 at 10:43:03AM +0800, Jason Wang wrote:
>
> On 2018/12/13 下午10:31, Michael S. Tsirkin wrote:
> > > Just to make sure I understand this. It looks to me we should:
> > >
> > > - allow passing GIOVA->GPA through UAPI
> > >
> > > - cache GIOVA->GPA somewhere but still use GIOVA->HVA in device IOTLB for
> > > performance
> > >
> > > Is this what you suggest?
> > >
> > > Thanks
> > Not really. We already have GPA->HVA, so I suggested a flag to pass
> > GIOVA->GPA in the IOTLB.
> >
> > This has advantages for security since a single table needs
> > then to be validated to ensure guest does not corrupt
> > QEMU memory.
> >
>
> I wonder how much we can gain through this. Currently, qemu IOMMU gives
> GIOVA->GPA mapping, and qemu vhost code will translate GPA to HVA then pass
> GIOVA->HVA to vhost. It looks no difference to me.
>
> Thanks
The difference is in security not in performance. Getting a bad HVA
corrupts QEMU memory and it might be guest controlled. Very risky. If
translations to HVA are done in a single place through a single table
it's safer as there's a single risky place.
--
MST
next prev parent reply other threads:[~2018-12-14 13:20 UTC|newest]
Thread overview: 23+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-12-12 10:08 [PATCH net V2 0/4] Fix various issue of vhost Jason Wang
2018-12-12 10:08 ` [PATCH net V2 1/4] vhost: make sure used idx is seen before log in vhost_add_used_n() Jason Wang
2018-12-12 14:33 ` Michael S. Tsirkin
2018-12-12 10:08 ` [PATCH net V2 2/4] vhost_net: switch to use mutex_trylock() in vhost_net_busy_poll() Jason Wang
2018-12-12 14:20 ` Michael S. Tsirkin
2018-12-12 10:08 ` [PATCH net V2 3/4] Revert "net: vhost: lock the vqs one by one" Jason Wang
2018-12-12 14:24 ` Michael S. Tsirkin
2018-12-13 2:27 ` Jason Wang
2018-12-12 10:08 ` [PATCH net V2 4/4] vhost: log dirty page correctly Jason Wang
2018-12-12 14:32 ` Michael S. Tsirkin
2018-12-13 2:39 ` Jason Wang
2018-12-13 14:31 ` Michael S. Tsirkin
2018-12-14 2:43 ` Jason Wang
2018-12-14 13:20 ` Michael S. Tsirkin [this message]
2018-12-24 3:43 ` Jason Wang
2018-12-24 17:41 ` Michael S. Tsirkin
2018-12-25 9:43 ` Jason Wang
2018-12-25 16:25 ` Michael S. Tsirkin
2018-12-26 5:43 ` Jason Wang
2018-12-26 13:46 ` Michael S. Tsirkin
2018-12-27 9:32 ` Jason Wang
2018-12-12 23:31 ` [PATCH net V2 0/4] Fix various issue of vhost David Miller
2018-12-13 2:42 ` Jason Wang
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=20181214081821-mutt-send-email-mst@kernel.org \
--to=mst@redhat.com \
--cc=jasowang@redhat.com \
--cc=jintack@cs.columbia.edu \
--cc=kvm@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--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).