Re: TDG quote analysis

[Sean Christopherson <seanjc@google.com>]

On Mon, Sep 21, 2026, Dave Hansen wrote:
> On 9/18/26 14:32, Sean Christopherson wrote:
> > By creating these system-wide thread pools, TDX has effectively created a bizarre
> > M:N scheduling problem, *and* introduced a completely avoidable noisy-neighbor
> > problem.
> 
> To be honest, I just want to chop all of the complexity out of this.
> 
> I want to assume that the TDX module can do one quote at a time. If that
> quote takes too long, software kills it and lets the next guy do a quote.
> 
> I don't even want to know that the TDX module *can* have 1 or 10 or 100
> quoting threads. I just want one which I can make sane rules around
> because 1 is *FINE*.

I'm not remotely convinced one per system is fine.  I'm all for one per VM, but
I'm pretty sure the SEAMCALL alone will have a measurable performance impact,
especially when factoring in that it will require a VMCS shootdown to do VMCLEAR
on the previous pCPU.  Mix in a few (tens of?) thousand more cycles, and any use
case that's trying to boot a decent number of TDX guests in parallel will be sad.