From: Paul Durrant <Paul.Durrant@citrix.com>
To: Andrew Cooper <Andrew.Cooper3@citrix.com>,
Anthony Perard <anthony.perard@citrix.com>,
"xen-devel@lists.xen.org" <xen-devel@lists.xen.org>,
Jan Beulich <jbeulich@suse.com>
Subject: Re: [RFC] Hypervisor, x86 emulation deprivileged
Date: Wed, 6 Jul 2016 07:59:11 +0000 [thread overview]
Message-ID: <a3cc25597c744dbdaf1f3339f2c1c036@AMSPEX02CL03.citrite.net> (raw)
In-Reply-To: <19019fa7-92c1-9016-61e6-97a798398864@citrix.com>
> -----Original Message-----
> From: Xen-devel [mailto:xen-devel-bounces@lists.xen.org] On Behalf Of
> Andrew Cooper
> Sent: 05 July 2016 18:26
> To: Anthony Perard; xen-devel@lists.xen.org; Jan Beulich
> Subject: Re: [Xen-devel] [RFC] Hypervisor, x86 emulation deprivileged
>
> On 05/07/16 12:22, Anthony PERARD wrote:
> > Hi,
> >
> > I've taken over the work from Ben to have a deprivileged mode in the
> > hypervisor, but I'm unsure about which direction to take.
>
> You should begin with an evaluation of available options, identifying
> which issues are mitigated, those which are not, and which which new
> risks are introduced.
>
Personally I can't see why we want to invent a new way of executing code in the hypervisor. What's wrong with modelling each emulator as a PV unikernel, running with all the usual domain and vcpu constructs? Doing anything else seems like:
a) a lot of work for little gain
b) re-inventing the wheel
Paul
> E.g.
>
> 1) De-privileging the x86 instruction emulator into hypervisor ring3
> Issues mitigated:
> * Out of bounds pointer accesses.
> Issues not mitigated:
> * On-stack state corruption.
> Risks:
> * Introduces what is basically 3rd type of vcpu, including all the
> subtly that comes user processes.
>
>
> Performance is strictly a secondary consideration; Make something which
> works first, then make it fast. Never the opposite way around.
>
> Another exercise which might be useful is to look at the recent XSAs and
> identified which of them could have been mitigated by one of the
> suggestions.
>
> ~Andrew
>
> _______________________________________________
> Xen-devel mailing list
> Xen-devel@lists.xen.org
> https://lists.xen.org/xen-devel
_______________________________________________
Xen-devel mailing list
Xen-devel@lists.xen.org
https://lists.xen.org/xen-devel
next prev parent reply other threads:[~2016-07-06 7:59 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-07-05 11:22 [RFC] Hypervisor, x86 emulation deprivileged Anthony PERARD
2016-07-05 12:58 ` George Dunlap
2016-07-05 17:20 ` Anthony PERARD
2016-07-05 13:02 ` Jan Beulich
2016-07-05 17:01 ` Anthony PERARD
2016-07-05 17:25 ` Andrew Cooper
2016-07-06 7:59 ` Paul Durrant [this message]
2016-07-08 9:07 ` Tim Deegan
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=a3cc25597c744dbdaf1f3339f2c1c036@AMSPEX02CL03.citrite.net \
--to=paul.durrant@citrix.com \
--cc=Andrew.Cooper3@citrix.com \
--cc=anthony.perard@citrix.com \
--cc=jbeulich@suse.com \
--cc=xen-devel@lists.xen.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).