Messages in this thread |  | | Date | Tue, 22 Nov 2022 07:14:14 -0800 | Subject | Re: [PATCH v7 06/20] x86/virt/tdx: Shut down TDX module in case of error | From | Dave Hansen <> |
| |
On 11/22/22 01:13, Peter Zijlstra wrote: > On Mon, Nov 21, 2022 at 01:26:28PM +1300, Kai Huang wrote: >> +/* >> + * Call the SEAMCALL on all online CPUs concurrently. Caller to check >> + * @sc->err to determine whether any SEAMCALL failed on any cpu. >> + */ >> +static void seamcall_on_each_cpu(struct seamcall_ctx *sc) >> +{ >> + on_each_cpu(seamcall_smp_call_function, sc, true); >> +} > > Suppose the user has NOHZ_FULL configured, and is already running > userspace that will terminate on interrupt (this is desired feature for > NOHZ_FULL), guess how happy they'll be if someone, on another parition, > manages to tickle this TDX gunk?
Yeah, they'll be none too happy.
But, what do we do?
There are technical solutions like detecting if NOHZ_FULL is in play and refusing to initialize TDX. There are also non-technical solutions like telling folks in the documentation that they better modprobe kvm early if they want to do TDX, or their NOHZ_FULL apps will pay.
We could also force the TDX module to be loaded early in boot before NOHZ_FULL is in play, but that would waste memory on TDX metadata even if TDX is never used.
How do NOHZ_FULL folks deal with late microcode updates, for example? Those are roughly equally disruptive to all CPUs.
|  |