Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67;
From:   Vitaly Kuznetsov <vkuznets@redhat.com>
To:     Roman Kagan <rkagan@virtuozzo.com>,
        Paolo Bonzini <pbonzini@redhat.com>
Cc:     kvm@vger.kernel.org,
        Radim =?utf-8?B?S3LEjW3DocWZ?= <rkrcmar@redhat.com>,
        "K. Y. Srinivasan" <kys@microsoft.com>,
        Haiyang Zhang <haiyangz@microsoft.com>,
        Stephen Hemminger <sthemmin@microsoft.com>,
        "Michael Kelley \(EOSG\)" <Michael.H.Kelley@microsoft.com>,
        Wanpeng Li <wanpeng.li@hotmail.com>,
        linux-kernel@vger.kernel.org
Subject: Re: [PATCH v4 RESEND 3/5] KVM: x86: hyperv: use get_vcpu_by_vpidx() in kvm_hv_flush_tlb()
In-Reply-To: <20180925101040.GA2336@rkaganb.sw.ru>
References: <20180822101832.31763-1-vkuznets@redhat.com> <20180822101832.31763-4-vkuznets@redhat.com> <8da03d2a-5405-f363-f081-e4bc46b106e3@redhat.com> <87r2hs7cco.fsf@vitty.brq.redhat.com> <87zhw62797.fsf@vitty.brq.redhat.com> <74055c3b-be66-4ce6-e727-a155f18a0ba1@redhat.com> <20180925085752.GA5391@rkaganb.sw.ru> <f8cd3988-ea7e-0e4a-ee95-927534276f84@redhat.com> <20180925101040.GA2336@rkaganb.sw.ru>
Date:   Tue, 25 Sep 2018 13:42:18 +0200
Message-ID: <871s9hreg5.fsf@vitty.brq.redhat.com>
MIME-Version: 1.0
Content-Type: text/plain
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

Roman Kagan <rkagan@virtuozzo.com> writes:

> 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.

Thanks guys,

I'll try to draft something up for v6.

-- 
Vitaly