linux-kernel - Re: [PATCH v19 091/130] KVM: TDX: remove use of struct vcpu_vmx from posted

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Date: Thu, 28 Mar 2024 14:10:36 -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 091/130] KVM: TDX: remove use of struct vcpu_vmx from
 posted_interrupt.c

On Thu, Mar 28, 2024 at 04:12:36PM +0800,
Chao Gao <chao.gao@...el.com> wrote:

> On Mon, Feb 26, 2024 at 12:26:33AM -0800, isaku.yamahata@...el.com wrote:
> >@@ -190,7 +211,8 @@ static bool vmx_needs_pi_wakeup(struct kvm_vcpu *vcpu)
> > 	 * notification vector is switched to the one that calls
> > 	 * back to the pi_wakeup_handler() function.
> > 	 */
> >-	return vmx_can_use_ipiv(vcpu) || vmx_can_use_vtd_pi(vcpu->kvm);
> >+	return (vmx_can_use_ipiv(vcpu) && !is_td_vcpu(vcpu)) ||
> >+		vmx_can_use_vtd_pi(vcpu->kvm);
> 
> It is better to separate this functional change from the code refactoring.

Agreed. Let's split this patch.


> > }
> > 
> > void vmx_vcpu_pi_put(struct kvm_vcpu *vcpu)
> >@@ -200,7 +222,8 @@ void vmx_vcpu_pi_put(struct kvm_vcpu *vcpu)
> > 	if (!vmx_needs_pi_wakeup(vcpu))
> > 		return;
> > 
> >-	if (kvm_vcpu_is_blocking(vcpu) && !vmx_interrupt_blocked(vcpu))
> >+	if (kvm_vcpu_is_blocking(vcpu) &&
> >+	    (is_td_vcpu(vcpu) || !vmx_interrupt_blocked(vcpu)))
> 
> Ditto.
> 
> This looks incorrect to me. here we assume interrupt is always enabled for TD.
> But on TDVMCALL(HLT), the guest tells KVM if hlt is called with interrupt
> disabled. KVM can just check that interrupt status passed from the guest.

That's true.  We can complicate this function and HLT emulation.  But I don't
think it's worthwhile because HLT with interrupt masked is rare.  Only for
CPU online.
-- 
Isaku Yamahata <isaku.yamahata@...el.com>