Re: [PATCH v2 41/58] i386/tdx: handle TDG.VP.VMCALL<GetQuote>

[Xiaoyao Li]

On 8/30/2023 1:18 PM, Chenyi Qiang wrote:
> On 8/29/2023 6:25 PM, Daniel P. Berrangé wrote:
> > On Tue, Aug 29, 2023 at 01:31:37PM +0800, Chenyi Qiang wrote:
> > > On 8/22/2023 4:24 PM, Daniel P. Berrangé wrote:
> > > > On Tue, Aug 22, 2023 at 08:52:30AM +0200, Markus Armbruster wrote:
> > > > > Xiaoyao Li <xiaoyao.li@intel.com> writes:
> > > > >
> > > > > > From: Isaku Yamahata <isaku.yamahata@intel.com>
> > > > > >
> > > > > > For GetQuote, delegate a request to Quote Generation Service.  Add property
> > > > > > of address of quote generation server and On request, connect to the
> > > > > > server, read request buffer from shared guest memory, send the request
> > > > > > buffer to the server and store the response into shared guest memory and
> > > > > > notify TD guest by interrupt.
> > > > > >
> > > > > > "quote-generation-service" is a property to specify Quote Generation
> > > > > > Service(QGS) in qemu socket address format.  The examples of the supported
> > > > > > format are "vsock:2:1234", "unix:/run/qgs", "localhost:1234".
> > > > > >
> > > > > > command line example:
> > > > > >    qemu-system-x86_64 \
> > > > > >      -object 'tdx-guest,id=tdx0,quote-generation-service=localhost:1234' \
> > > > > >      -machine confidential-guest-support=tdx0
> > > > > >
> > > > > > Signed-off-by: Isaku Yamahata <isaku.yamahata@intel.com>
> > > > > > Signed-off-by: Xiaoyao Li <xiaoyao.li@intel.com>
> > > > > > ---
> > > > > >   qapi/qom.json         |   5 +-
> > > > > >   target/i386/kvm/tdx.c | 380 ++++++++++++++++++++++++++++++++++++++++++
> > > > > >   target/i386/kvm/tdx.h |   7 +
> > > > > >   3 files changed, 391 insertions(+), 1 deletion(-)
> > > > > >
> > > > > > diff --git a/qapi/qom.json b/qapi/qom.json
> > > > > > index 87c1d440f331..37139949d761 100644
> > > > > > --- a/qapi/qom.json
> > > > > > +++ b/qapi/qom.json
> > > > > > @@ -879,13 +879,16 @@
> > > > > >   #
> > > > > >   # @mrownerconfig: MROWNERCONFIG SHA384 hex string of 48 * 2 length (default: 
> > > > > > 0)
> > > > > >   #
> > > > > > +# @quote-generation-service: socket address for Quote Generation Service(QGS)
> > > > > > +#
> > > > > >   # Since: 8.2
> > > > > >   ##
> > > > > >   { 'struct': 'TdxGuestProperties',
> > > > > >     'data': { '*sept-ve-disable': 'bool',
> > > > > >               '*mrconfigid': 'str',
> > > > > >               '*mrowner': 'str',
> > > > > > -            '*mrownerconfig': 'str' } }
> > > > > > +            '*mrownerconfig': 'str',
> > > > > > +            '*quote-generation-service': 'str' } }
> > > > >
> > > > > Why not type SocketAddress?
> > > >
> > > > Yes, the code uses SocketAddress internally when it eventually
> > > > calls qio_channel_socket_connect_async(), so we should directly
> > > > use SocketAddress in the QAPI from the start.
> > >
> > > Any benefit to directly use SocketAddress?
> >
> > We don't want whatever code consumes the configuration to
> > do a second level of parsing to convert the 'str' value
> > into the 'SocketAddress' object it actually needs.
> >
> > QEMU has a long history of having a second round of ad-hoc
> > parsing of configuration and we've found it to be a serious
> > maintenence burden. Thus we strive to have everything
> > represented in QAPI using the desired final type, and avoid
> > the second round of parsing.
>
> Thanks for your explanation.
>
> > > "quote-generation-service" here is optional, it seems not trivial to add
> > > and parse the SocketAddress type in QEMU command. After I change 'str'
> > > to 'SocketAddress' and specify the command like "-object
> > > tdx-guest,type=vsock,cid=2,port=1234...", it will report "invalid
> > > parameter cid".
> >
> > The -object parameter supports JSON syntax for this reason
> >
> >     -object '{"qom-type":"tdx-guest","quote-generation-service":{"type": "vsock", 
> > "cid":"2","port":"1234"}}'
> >
> > libvirt will always use the JSON syntax for -object with a new enough
> > QEMU.
>
> The JSON syntax works for me. Then, we need to add some doc about using
> JSON syntax when quote-generation-service is required.

This limitation doesn't look reasonable to me.

@Daniel,

Is it acceptable by QEMU community?

> > With regards,
> > Daniel