Re: [PATCH v19 070/130] KVM: TDX: TDP MMU TDX support

[Chao Gao]

>+#if IS_ENABLED(CONFIG_HYPERV)
>+static int vt_flush_remote_tlbs(struct kvm *kvm);
>+#endif
>+
> static __init int vt_hardware_setup(void)
> {
> 	int ret;
>@@ -49,11 +53,29 @@ static __init int vt_hardware_setup(void)
> 		pr_warn_ratelimited("TDX requires mmio caching.  Please enable mmio caching for TDX.\n");
> 	}
> 
>+#if IS_ENABLED(CONFIG_HYPERV)
>+	/*
>+	 * TDX KVM overrides flush_remote_tlbs method and assumes
>+	 * flush_remote_tlbs_range = NULL that falls back to
>+	 * flush_remote_tlbs.  Disable TDX if there are conflicts.
>+	 */
>+	if (vt_x86_ops.flush_remote_tlbs ||
>+	    vt_x86_ops.flush_remote_tlbs_range) {
>+		enable_tdx = false;
>+		pr_warn_ratelimited("TDX requires baremetal. Not Supported on VMM guest.\n");
>+	}
>+#endif
>+
> 	enable_tdx = enable_tdx && !tdx_hardware_setup(&vt_x86_ops);
> 	if (enable_tdx)
> 		vt_x86_ops.vm_size = max_t(unsigned int, vt_x86_ops.vm_size,
> 					   sizeof(struct kvm_tdx));
> 
>+#if IS_ENABLED(CONFIG_HYPERV)
>+	if (enable_tdx)
>+		vt_x86_ops.flush_remote_tlbs = vt_flush_remote_tlbs;

Is this hook necessary/beneficial to TDX?

if no, we can leave .flush_remote_tlbs as NULL. if yes, we should do:

struct kvm_x86_ops {
..
#if IS_ENABLED(CONFIG_HYPERV) || IS_ENABLED(TDX...)
	int  (*flush_remote_tlbs)(struct kvm *kvm);
	int  (*flush_remote_tlbs_range)(struct kvm *kvm, gfn_t gfn,
					gfn_t nr_pages);
#endif