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Re: [PATCH v5 49/65] i386/tdx: handle TDG.VP.VMCALL<GetQuote>


From: Xiaoyao Li
Subject: Re: [PATCH v5 49/65] i386/tdx: handle TDG.VP.VMCALL<GetQuote>
Date: Thu, 7 Mar 2024 19:25:48 +0800
User-agent: Mozilla Thunderbird

On 2/29/2024 9:28 PM, Markus Armbruster wrote:
Xiaoyao Li <xiaoyao.li@intel.com> writes:

On 2/29/2024 4:40 PM, Markus Armbruster wrote:
Xiaoyao Li <xiaoyao.li@intel.com> writes:

From: Isaku Yamahata <isaku.yamahata@intel.com>

Add property "quote-generation-socket" to tdx-guest, which is a property
of type SocketAddress to specify Quote Generation Service(QGS).

On request of GetQuote, it connects to the QGS socket, read request
data from shared guest memory, send the request data to the QGS,
and store the response into shared guest memory, at last notify
TD guest by interrupt.

command line example:
    qemu-system-x86_64 \
      -object '{"qom-type":"tdx-guest","id":"tdx0","quote-generation-socket":{"type": "vsock", 
"cid":"1","port":"1234"}}' \
      -machine confidential-guest-support=tdx0

Note, above example uses vsock type socket because the QGS we used
implements the vsock socket. It can be other types, like UNIX socket,
which depends on the implementation of QGS.

To avoid no response from QGS server, setup a timer for the transaction.
If timeout, make it an error and interrupt guest. Define the threshold of
time to 30s at present, maybe change to other value if not appropriate.

Signed-off-by: Isaku Yamahata <isaku.yamahata@intel.com>
Codeveloped-by: Chenyi Qiang <chenyi.qiang@intel.com>
Signed-off-by: Chenyi Qiang <chenyi.qiang@intel.com>
Codeveloped-by: Xiaoyao Li <xiaoyao.li@intel.com>
Signed-off-by: Xiaoyao Li <xiaoyao.li@intel.com>

[...]

diff --git a/qapi/qom.json b/qapi/qom.json
index cac875349a3a..7b26b0a0d3aa 100644
--- a/qapi/qom.json
+++ b/qapi/qom.json
@@ -917,13 +917,19 @@
  #     (base64 encoded SHA384 digest). (A default value 0 of SHA384 is
  #     used when absent).
  #
+# @quote-generation-socket: socket address for Quote Generation
+#     Service (QGS).  QGS is a daemon running on the host.  User in
+#     TD guest cannot get TD quoting for attestation if QGS is not
+#     provided.  So admin should always provide it.

This makes me wonder why it's optional.  Can you describe a use case for
*not* specifying @quote-generation-socket?

Maybe at last when all the TDX support lands on all the components, attestation 
will become a must for a TD guest to be usable.

However, at least for today, booting and running a TD guest don't require 
attestation. So not provide it, doesn't affect anything excepting cannot get a 
Quote.

Maybe

   # @quote-generation-socket: Socket address for Quote Generation
   #     Service (QGS).  QGS is a daemon running on the host.  Without
   #     it, the guest will not be able to get a TD quote for
   #     attestation.

Thanks! will update to it.

[...]





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