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

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Message-ID: <ZgTgOVNmyVVgfvFM@chao-email>
Date: Thu, 28 Mar 2024 11:12:57 +0800
From: Chao Gao <chao.gao@...el.com>
To: <isaku.yamahata@...el.com>
CC: <kvm@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
	<isaku.yamahata@...il.com>, Paolo Bonzini <pbonzini@...hat.com>,
	<erdemaktas@...gle.com>, Sean Christopherson <seanjc@...gle.com>, Sagi Shahar
	<sagis@...gle.com>, Kai Huang <kai.huang@...el.com>, <chen.bo@...el.com>,
	<hang.yuan@...el.com>, <tina.zhang@...el.com>
Subject: Re: [PATCH v19 070/130] KVM: TDX: TDP MMU TDX support

>+#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