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

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Message-ID: <20220620105957.GA9496@gao-cwp>
Date:   Mon, 20 Jun 2022 19:00:02 +0800
From:   Chao Gao <chao.gao@...el.com>
To:     Shenming Lu <lushenming@...edance.com>
Cc:     Zeng Guang <guang.zeng@...el.com>,
        Paolo Bonzini <pbonzini@...hat.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>, x86@...nel.org,
        linux-kernel@...r.kernel.org, Robert Hu <robert.hu@...el.com>,
        zhouyibo@...edance.com
Subject: Re: [External] [PATCH v9 9/9] KVM: VMX: enable IPI virtualization

On Mon, Jun 20, 2022 at 06:02:32PM +0800, Shenming Lu wrote:
>> +		if (enable_ipiv)
>> +			tertiary_exec_controls_clearbit(vmx, TERTIARY_EXEC_IPI_VIRT);
>> +	}
>>   	vmx_update_msr_bitmap_x2apic(vcpu);
>>   }
>
>Hi, just a small question here:
>
>It seems that we clear the TERTIARY_EXEC_IPI_VIRT bit before enabling
>interception for APIC_ICR when deactivating APICv on some reason.
>Is there any problem with this sequence?

Both are done before the next vCPU entry. As long as no guest code can
run between them (APICv setting takes effect in guest), this sequence
shouldn't have any problem.