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

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Message-ID: <20240328035537.GN2444378@ls.amr.corp.intel.com>
Date: Wed, 27 Mar 2024 20:55:37 -0700
From: Isaku Yamahata <isaku.yamahata@...el.com>
To: Chao Gao <chao.gao@...el.com>
Cc: isaku.yamahata@...el.com, 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,
	isaku.yamahata@...ux.intel.com
Subject: Re: [PATCH v19 070/130] KVM: TDX: TDP MMU TDX support

On Thu, Mar 28, 2024 at 11:12:57AM +0800,
Chao Gao <chao.gao@...el.com> wrote:

> >+#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

Will fix it. I made mistake when I rebased it. Now those hooks are only for
CONFIG_HPYERV.
-- 
Isaku Yamahata <isaku.yamahata@...el.com>