linux-kernel - Re: [PATCH v9 9/9] KVM: VMX: enable IPI virtualization

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Date:   Mon, 2 May 2022 18:16:13 +0200
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     Zeng Guang <guang.zeng@...el.com>,
        Sean Christopherson <seanjc@...gle.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Joerg Roedel <joro@...tes.org>, kvm@...r.kernel.org,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Tony Luck <tony.luck@...el.com>,
        Kan Liang <kan.liang@...ux.intel.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        "H. Peter Anvin" <hpa@...or.com>,
        Kim Phillips <kim.phillips@....com>,
        Jarkko Sakkinen <jarkko@...nel.org>,
        Jethro Beekman <jethro@...tanix.com>,
        Kai Huang <kai.huang@...el.com>
Cc:     x86@...nel.org, linux-kernel@...r.kernel.org,
        Robert Hu <robert.hu@...el.com>, Gao Chao <chao.gao@...el.com>
Subject: Re: [PATCH v9 9/9] KVM: VMX: enable IPI virtualization

On 4/19/22 17:45, Zeng Guang wrote:
> +static bool vmx_can_use_pi_wakeup(struct kvm_vcpu *vcpu)
> +{
> +	/*
> +	 * If a blocked vCPU can be the target of posted interrupts,
> +	 * switching notification vector is needed so that kernel can
> +	 * be informed when an interrupt is posted and get the chance
> +	 * to wake up the blocked vCPU. For now, using posted interrupt
> +	 * for vCPU wakeup when IPI virtualization or VT-d PI can be
> +	 * enabled.
> +	 */
> +	return vmx_can_use_ipiv(vcpu) || vmx_can_use_vtd_pi(vcpu->kvm);
> +}

Slightly more accurate name and comment:

static bool vmx_needs_pi_wakeup(struct kvm_vcpu *vcpu)
{
         /*
          * The default posted interrupt vector does nothing when
          * invoked outside guest mode.   Return whether a blocked vCPU
          * can be the target of posted interrupts, as is the case when
          * using either IPI virtualization or VT-d PI, so that the
          * 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);
}


Paolo