linux-kernel - Re: [PATCH 2/4] KVM: VMX: avoid double list add with VT-d posted interrupts

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Message-ID: <5cfad7aa-9069-5419-b0b3-41df74a4f551@redhat.com>
Date:   Thu, 8 Jun 2017 13:24:44 +0200
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     Peter Xu <peterx@...hat.com>
Cc:     linux-kernel@...r.kernel.org, kvm@...r.kernel.org,
        Longpeng <longpeng2@...wei.com>,
        Huangweidong <weidong.huang@...wei.com>,
        Gonglei <arei.gonglei@...wei.com>,
        wangxin <wangxinxin.wang@...wei.com>,
        Radim Krčmář <rkrcmar@...hat.com>
Subject: Re: [PATCH 2/4] KVM: VMX: avoid double list add with VT-d posted
 interrupts



On 08/06/2017 11:16, Peter Xu wrote:
>> Oh, I see what you mean: set up the wakeup handler in vmx_vcpu_pi_put
>> and rely on PI.ON to wake up the sleeping process immediately.  That
>> should be feasible, but overall I like the current pre_block/post_block
>> structure, and I think it's simpler.  The only thing to be careful about
>> is leaving the IRTE unmodified when scheduling out a blocked VCPU, which
>> is cleaned up and simplified in patch 3.
>>
>> So I understand that the state may seem a bit too complicated as
>> of this patch, but hopefully the next two make it clearer.
> After re-read the codes and patches I got the point. Indeed current
> way should be clearer since pre/post_block are mostly handling NV/DST
> while pi_load/put are for SN bit.  Thanks!

Almost: pi_load handles NDST too.  However, I think with patch 3 it's
clearer how pi_load handles the nesting inside pre_block...post_block.

Thanks,

Paolo