linux-kernel - The vcpu won't be wakened for a long time

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Date:   Tue, 14 Dec 2021 13:55:38 +0000
From:   "Longpeng (Mike, Cloud Infrastructure Service Product Dept.)" 
        <longpeng2@...wei.com>
To:     "pbonzini@...hat.com" <pbonzini@...hat.com>,
        "kvm@...r.kernel.org" <kvm@...r.kernel.org>
CC:     "Gonglei (Arei)" <arei.gonglei@...wei.com>,
        Huangzhichao <huangzhichao@...wei.com>,
        "seanjc@...gle.com" <seanjc@...gle.com>,
        "Wanpeng Li" <wanpengli@...cent.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        "Jim Mattson" <jmattson@...gle.com>,
        Joerg Roedel <joro@...tes.org>,
        linux-kernel <linux-kernel@...r.kernel.org>
Subject: The vcpu won't be wakened for a long time

Hi guys,

We find a problem in kvm_vcpu_block().

The testcase is:
 - VM configured with 1 vcpu and 1 VF (using vfio-pci passthrough)
 - the vfio interrupt and the vcpu are bound to the same pcpu
 - using remapped mode IRTE, NOT posted mode

The bug was triggered when the vcpu executed HLT instruction:

kvm_vcpu_block:
    prepare_to_rcuwait(&vcpu->wait);
    for (;;) {
        set_current_state(TASK_INTERRUPTIBLE);

        if (kvm_vcpu_check_block(vcpu) < 0)
            break;
					<------------ (*)
        waited = true;
        schedule();
    }
    finish_rcuwait(&vcpu->wait);

The vcpu will go to sleep even if an interrupt from the VF is fired at (*) and
the PIR and ON bit will be set ( in vmx_deliver_posted_interrupt ), so the vcpu
won't be wakened by subsequent interrupts.

Any suggestions ? Thanks.