linux-kernel - Re: [PATCH v4 RESEND 3/5] KVM: x86: hyperv: use get_vcpu_by_vpidx() in kvm_hv_flush

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Message-ID: <20180925101040.GA2336@rkaganb.sw.ru>
Date:   Tue, 25 Sep 2018 13:10:41 +0300
From:   Roman Kagan <rkagan@...tuozzo.com>
To:     Paolo Bonzini <pbonzini@...hat.com>
Cc:     Vitaly Kuznetsov <vkuznets@...hat.com>, kvm@...r.kernel.org,
        Radim Krčmář <rkrcmar@...hat.com>,
        "K. Y. Srinivasan" <kys@...rosoft.com>,
        Haiyang Zhang <haiyangz@...rosoft.com>,
        Stephen Hemminger <sthemmin@...rosoft.com>,
        "Michael Kelley (EOSG)" <Michael.H.Kelley@...rosoft.com>,
        Wanpeng Li <wanpeng.li@...mail.com>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v4 RESEND 3/5] KVM: x86: hyperv: use get_vcpu_by_vpidx()
 in kvm_hv_flush_tlb()

On Tue, Sep 25, 2018 at 11:29:57AM +0200, Paolo Bonzini wrote:
> On 25/09/2018 10:57, Roman Kagan wrote:
> > If we can assume that in all relevant cases vp_index coincides with the
> > cpu index (which I think we can) then Vitaly's approach is the most
> > efficient.
> > 
> > If, on the opposite, we want to optimize for random mapping between
> > vp_index and cpu index, then it's probably better instead to iterate
> > over vcpus and test if their vp_index belongs to the requested mask.
> 
> Yes, that would work too.  Perhaps we can do both?  You can have a
> kvm->num_mismatched_vp_indexes count to choose between the two.

Makes sense to me.

Roman.