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From:   Vitaly Kuznetsov <vkuznets@redhat.com>
To:     Paolo Bonzini <pbonzini@redhat.com>,
        Roman Kagan <rkagan@virtuozzo.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>,
        Mohammed Gamal <mmorsy@redhat.com>,
        Cathy Avery <cavery@redhat.com>,
        Wanpeng Li <wanpeng.li@hotmail.com>,
        linux-kernel@vger.kernel.org
Subject: Re: [PATCH v6 7/7] KVM: x86: hyperv: implement PV IPI send hypercalls
In-Reply-To: <51ff55e0-9d8d-73be-e0e7-f8580bc0206e@redhat.com>
References: <20180926170259.29796-1-vkuznets@redhat.com> <20180926170259.29796-8-vkuznets@redhat.com> <20180927110711.GE4186@rkaganb.sw.ru> <51ff55e0-9d8d-73be-e0e7-f8580bc0206e@redhat.com>
Date:   Mon, 01 Oct 2018 18:20:36 +0200
Message-ID: <877ej1fxkb.fsf@vitty.brq.redhat.com>
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Paolo Bonzini <pbonzini@redhat.com> writes:

> On 27/09/2018 13:07, Roman Kagan wrote:
...
>> 
>> I must say that now it looks even more tempting to follow the same
>> pattern as your kvm_hv_flush_tlb: define a function that would call
>> kvm_apic_set_irq() on all vcpus in a mask (optimizing the all-set case
>> with a NULL mask), and make kvm_hv_send_ipi perform the same hv_vp_set
>> -> vcpu_mask transformation followed by calling into that function.
>
>
> It would perhaps be cleaner, but really kvm_apic_set_irq is as efficient
> as it can be, since it takes the destination vcpu directly.
>
> The code duplication for walking the sparse set is a bit ugly, perhaps
> that could be changed to use an iterator macro.

I actually like Roman's suggestion on how to re-write kvm_hv_flush_tlb()
and I also agree that it would be easier for future readers if we write
kvm_hv_send_ipi() in a similar way. Actually, I already have v7 in my
stash, will be sending it out shortly.

-- 
Vitaly