On Mon, 2023-02-13 at 14:28 -0800, Dave Hansen wrote: > On 2/13/23 13:13, Huang, Kai wrote: > > Perhaps I didn't explain clearly in the comment. Below is the updated one: > > > > /* > > * 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 w/o doing per-cpu initialization. > > * > > * For example, a new CPU can become online when KVM is > > * unloaded, in which case tdx_cpu_enable() is not called since > > * KVM's CPU online callback has been removed. > > * > > * 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. > > */ > > This is voodoo. > > I want a TDX-specific hotplug CPU handler. Period. Please make that > happen. > Yes 100% agreed. > Put that code in this patch. That handler should: > > 1. Run after the KVM handler (if present) > 2. See if VMX is on > 3. If VMX is on: > 3a. Run smp_func_module_lp_init(), else > 3b. Mark the CPU as needing smp_func_module_lp_init() > > Then, in the 'case TDX_MODULE_INITIALIZED:', you call a function to > iterate over the cpumask that was generated in 3b. > > That makes the handoff *EXPLICIT*. You know exactly which CPUs need > what done to them. A CPU hotplug either explicitly involves doing the > work to make TDX work on the CPU, or explicitly defers the work to a > specific later time in a specific later piece of code. In 3b. we don't need to "explicitly mark the CPU as needing smp_func_module_lp_init()". We already have __cpu_tdx_mask to track whether LP.INIT has been done on one cpu and we can use that to determine: Any online cpu which isn't set in __cpu_tdx_mask needs to do LP.INIT in tdx_enable(). And the function module_lp_init_online_cpus() already handles that, and it can be called directly in tdx_enable() path (as shown in this patch). I'll do above as you suggested, but just use __cpu_tdx_mask as explained above. ( My main concern is "Run after the KVM handler" seems a little bit hacky to me. Logically, it's more reasonable to have the TDX callback _before_ KVM's but not _after_. If any user (KVM) has done tdx_enable() successfully, the TDX code should give the user a "TDX-runnable" cpu before user (KVM)'s own callback is involved. Anyway as mentioned above, I'll do above as you suggested.)
