Re: [RFC PATCH v3 18/59] KVM: x86: Add flag to mark TSC as immutable (for TDX)

Thomas Gleixner
2021-11-25T19:42:26Z

On Wed, Nov 24 2021 at 16:20, isaku yamahata wrote:
> From: Sean Christopherson <sean.j.christopherson@intel.com>
>
> The TSC for TDX1 guests is fixed at TD creation time. Add tsc_immutable

What's a TDX1 guest?

> to reflect that the TSC of the guest cannot be changed in any way, and
> use it to short circuit all paths that lead to one of the myriad TSC
> adjustment flows.

I can kinda see the reason for this being valuable on it's own, but in
general why does TDX need a gazillion flags to disable tons of different
things if _ALL_ these flags are going to be set by for TDX guests
anyway?

Seperate flags make only sense when they have a value on their own,
i.e. are useful for things outside of TDX. If not they are just useless
ballast.

Thanks,

tglx