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Date:   Wed, 31 Aug 2022 16:47:25 +0000
From:   Sean Christopherson <seanjc@google.com>
To:     Maxim Levitsky <mlevitsk@redhat.com>
Cc:     Paolo Bonzini <pbonzini@redhat.com>, kvm@vger.kernel.org,
        linux-kernel@vger.kernel.org,
        Suravee Suthikulpanit <suravee.suthikulpanit@amd.com>,
        Li RongQing <lirongqing@baidu.com>
Subject: Re: [PATCH 15/19] KVM: x86: Explicitly skip optimized logical map
 setup if vCPU's LDR==0
Message-ID: <Yw+QnR8xu23ToD9g@google.com>
References: <20220831003506.4117148-1-seanjc@google.com>
 <20220831003506.4117148-16-seanjc@google.com>
 <0459cd1568afdbb451190518c2bdaa5a821987df.camel@redhat.com>
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On Wed, Aug 31, 2022, Maxim Levitsky wrote:
> On Wed, 2022-08-31 at 00:35 +0000, Sean Christopherson wrote:
> > Explicitly skip the optimized map setup if the vCPU's LDR is '0', i.e. if
> > the vCPU will never response to logical mode interrupts.  KVM already
> > skips setup in this case, but relies on kvm_apic_map_get_logical_dest()
> > to generate mask==0.  KVM still needs the mask=0 check as a non-zero LDR
> > can yield mask==0 depending on the mode, but explicitly handling the LDR
> > will make it simpler to clean up the logical mode tracking in the future.
> 
> If I am not mistaken, the commit description is a bit misleading - in this
> case we just don't add the vCPU to the map since it is unreachable, but we do
> continue creating the map.

I'll reword.  I intended that to mean "skip the optimized setup for the vCPU", but
even that is unnecessarily confusing.