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

["Daniel P. Berrangé" <berrange@redhat.com>]

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.

> "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.

With regards,
Daniel
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