linux-kernel - Re: [PATCH v19 043/130] KVM: TDX: create/free TDX vcpu structure

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Date: Thu, 21 Mar 2024 13:21:50 -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 043/130] KVM: TDX: create/free TDX vcpu structure

On Thu, Mar 21, 2024 at 09:30:12AM +0800,
Chao Gao <chao.gao@...el.com> wrote:

> >+int tdx_vcpu_create(struct kvm_vcpu *vcpu)
> >+{
> >+	struct kvm_tdx *kvm_tdx = to_kvm_tdx(vcpu->kvm);
> >+
> >+	WARN_ON_ONCE(vcpu->arch.cpuid_entries);
> >+	WARN_ON_ONCE(vcpu->arch.cpuid_nent);
> >+
> >+	/* TDX only supports x2APIC, which requires an in-kernel local APIC. */
> 
> Cannot QEMU emulate x2APIC? In my understanding, the reason is TDX module always
> enables APICv for TDs. So, KVM cannot intercept every access to APIC and forward
> them to QEMU for emulation.

You're right. Let me update it as follows.

  /*
   * TDX module always enables APICv for TDs. So, KVM cannot intercept every
   * access to APIC and forward them to user space VMM.
   */



> >+	if (!vcpu->arch.apic)
> 
> will "if (!irqchip_in_kernel(vcpu->kvm))" work? looks this is the custome for such
> a check.


It should work because kvm_arch_vcpu_create().  Will update it.
-- 
Isaku Yamahata <isaku.yamahata@...el.com>