linux-kernel - Re: [PATCH v2] KVM: x86: check PIR even for vCPUs with disabled APICv

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Message-ID: <4316fbc5-b758-a7c6-530d-dc5a97f4e97b@redhat.com>
Date:   Thu, 18 Nov 2021 18:56:34 +0100
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     Sean Christopherson <seanjc@...gle.com>
Cc:     Maxim Levitsky <mlevitsk@...hat.com>, linux-kernel@...r.kernel.org,
        kvm@...r.kernel.org, stable@...r.kernel.org
Subject: Re: [PATCH v2] KVM: x86: check PIR even for vCPUs with disabled APICv

On 11/18/21 17:17, Sean Christopherson wrote:
> On Thu, Nov 18, 2021, Paolo Bonzini wrote:
>> On 11/18/21 10:56, Maxim Levitsky wrote:
>>> vmx_sync_pir_to_irr has 'if (KVM_BUG_ON(!vcpu->arch.apicv_active,
>>> vcpu->kvm))' That has to be removed I think for this to work.
>>
>> Good point.
> 
> Hmm, I think I'd prefer to keep it as
> 
> 	if (KVM_BUG_ON(!enable_apicv))
> 		return -EIO;
> 
> since calling it directly or failing to nullify vmx_x86_ops.sync_pir_to_irr when
> APICv is unsupported would lead to all sorts of errors.  It's not a strong
> preference though.
> 

Sure, why not.  There's a few more changes required to handle 
KVM_REQ_EVENT when APICv is !active on the CPU, so I'll post it early 
next week.

(The MOVE/COPY context stuff also exposed itself as a bit of a 
trainwreck and ate half of my day).

Paolo