Re: [🚨ext] Re: [PATCH v3 0/2] virt: tdx-guest: Fix and speed up the wait for a Quote

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

On Tue, 2026-11-03 at 09:56 +0000, Moe Mahhouk wrote:
> On Mon, 2026-11-02 at 19:55 +0000, Edgecombe, Rick P wrote:
> > Long term though, isn't this a better option? This patch is
> > essentially a performance optimization.
> 
> Agreed that interrupt-driven completion is the better end state where the
> VMM supports it. But I don't think it can replace polling.
> SetupEventNotifyInterrupt is optional in the GHCI and enumerated through
> GetTdVmCallInfo. KVM only forwards it to userspace (since v6.16), and a
> VMM that doesn't implement it returns SUBFUNC_UNSUPPORTED. So the guest
> still needs a polling fallback for older KVM/QEMU and for other VMMs.
> Patch 2 is about that fallback.

We do expect quote execution time to change, so this may not be optimal long
term. The exponential backoff could limit it to 2x the real quote time. For a
long quote this could be pretty long. I'd almost wonder if the guest would
normally be happy to spend more cycles on getting a faster quote. Can you
explain more about the quote use case you are targeting?