Re: [PATCH v9 07/18] x86/virt/tdx: Do TDX module per-cpu initialization

Peter Zijlstra
2023-02-14T16:02:21Z

On Mon, Feb 13, 2023 at 10:07:30AM -0800, Dave Hansen wrote:
> On 2/13/23 03:59, Kai Huang wrote:
> > @@ -247,8 +395,17 @@ int tdx_enable(void)
> > ret = __tdx_enable();
> > break;
> > case TDX_MODULE_INITIALIZED:
> > - /* Already initialized, great, tell the caller. */
> > - ret = 0;
> > + /*
> > + * The previous call of __tdx_enable() may only have
> > + * initialized part of present cpus during module
> > + * initialization, and new cpus may have become online
> > + * since then.
> > + *
> > + * To make sure all online cpus are TDX-runnable, always
> > + * do per-cpu initialization for all online cpus here
> > + * even the module has been initialized.
> > + */
> > + ret = __tdx_enable_online_cpus();
>
> I'm missing something here. CPUs get initialized through either:
>
> 1. __tdx_enable(), for the CPUs around at the time
> 2. tdx_cpu_online(), for hotplugged CPUs after __tdx_enable()
>
> But, this is a third class. CPUs that came online after #1, but which
> got missed by #2. How can that happen?

offline CPUs, start TDX crap, online CPUs.