Re: TDG quote analysis

["Edgecombe, Rick P" <rick.p.edgecombe@intel.com>]

On Tue, 2026-09-22 at 06:48 +0000, Reshetova, Elena wrote:
> Hope this clarifies how to calculate memory impact. 

Sean is suggesting to have some save state area per-TD such that each TD can get
a quote without interfering with the other. I think this is saying inside TDX
module you need a "vCPU" and a "session", at which point you can execute
independently from the other quotes. Together that would take:

2 + 2 + 6 = 8 pages = 40KB?

(BTW not following the "* 2 + 2" bit, how does that square with "Quoting Service
is luckily the one that needs very little, but it does consume a single 4KB
page"?)

And then the quoting TD itself could be, I'd guess at least in the MB range?

So the two options:
One operation at a time per-system: A few MBs + 40KB + contention handling
One operation at a time per-TD: A few MBs + 40KB * NUM_TDs

Outside of the S3M based attestation type schemes, the per-TD solution seems
simpler to me. No one needs to think about contention. (except for inter-guest
contention) And it eliminates ever needing to configure contention handling
parameters from the host.

Then we leave contention handling for another day? In a way, the save state per-
TD solution is in the spirit of punting, because it makes the whole thing
simpler today and will require more work for an S3M each-each quote thing.

But that "simpler" is only about contention. We still have some opens on what
TDG extension calls need to handle. Dave, something else we were discussing up
the thread is whether a TDG quote call needs to have some
INTERRUBTIBLE_RESUMABLE behavior from the guest. So that the guest can take a
break from the long running guest call in order to handle *guest* interrupts. Do
we have the same concern there that we do in the host?