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Re: [Qemu-ppc] [PATCH v2] spapr-rtas: add ibm, get-vpd RTAS interface


From: Murilo Opsfelder Araujo
Subject: Re: [Qemu-ppc] [PATCH v2] spapr-rtas: add ibm, get-vpd RTAS interface
Date: Tue, 26 Feb 2019 14:08:30 -0300
User-agent: Mutt/1.11.3 (2019-02-01)

Hi, Maxiwell.

On Tue, Feb 26, 2019 at 11:21:26AM -0300, Maxiwell S. Garcia wrote:
> On Tue, Feb 26, 2019 at 02:21:03PM +1100, David Gibson wrote:
> > On Mon, Feb 25, 2019 at 08:20:09PM -0300, Murilo Opsfelder Araujo wrote:
> > > Hi, Maxiwell.
> > >
> > > On Mon, Feb 25, 2019 at 01:23:25PM -0300, Maxiwell S. Garcia wrote:
> > > > This adds a handler for ibm,get-vpd RTAS calls, allowing pseries
> > > > guest to collect host information. It is disabled by default to
> > > > avoid unwanted information leakage. To enable it, use:
> > > > ‘-M pseries,vpd-export=on’
> > >
> > > The patch for setting host-serial and host-model already landed Gibson's
> > > ppc-for-4.0 branch:
> > >
> > >   commit 9e584f45868f6945c1282c938278038cba0e4af2
> > >   Author: Prasad J Pandit <address@hidden>
> > >   Date:   Mon Feb 18 23:43:49 2019 +0530
> > >
> > >       ppc: add host-serial and host-model machine attributes 
> > > (CVE-2019-8934)
> > >
> > >
> > > QEMU should only return host-serial and host-model from the host if the
> > > following combination of parameters are provided:
> > >
> > >   -M host-serial=passthrough,host-model=passthrough,vpd-export=on
> > >
> > > If host-serial or host-model are set with a user-string, ibm,get-vpd 
> > > should
> > > honor these values and return them, not exposing host information by 
> > > accident.
> > >
> > > I'm not even sure if we need vpd-export=<bool> setting. Its logic could be
> > > derived from the presence of host-serial=passthrough and 
> > > host-model=passthrough
> > > options.
> > >
> > > What do you think?
> >
> > That's an excellent point - I hadn't thought through the fact that
> > this is the same information exposed by those properties.  I do indeed
> > think that exposing the same information set in those properties - and
> > thereby avoiding the new machine option - would be a better plan.
> >
>
> I saw that the patch was applied. So I will work in another patch
> to use these properties and remove the export-vpd option.
>
> Another thing that I thought the fact that 'host-serial' and 'host-model'
> nodes in Device Tree are not in accordance with LoPAPR document. What
> you think in use only get-vpd to get these information and remove
> nodes from device tree?

Both "system-id" and "model" properties are described in the section "3.3.2.1
Root Node Properties" of the "Device Tree Bindings: Linux on Power Architecture
Reference" document:

  https://members.openpowerfoundation.org/wg/SYSSW/document/1455

--
Murilo




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