linux-kernel - Re: [PATCH v6 7/7] KVM: x86: hyperv: implement PV IPI send hypercalls

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Message-ID: <877ej1fxkb.fsf@vitty.brq.redhat.com>
Date:   Mon, 01 Oct 2018 18:20:36 +0200
From:   Vitaly Kuznetsov <vkuznets@...hat.com>
To:     Paolo Bonzini <pbonzini@...hat.com>,
        Roman Kagan <rkagan@...tuozzo.com>
Cc:     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>,
        Mohammed Gamal <mmorsy@...hat.com>,
        Cathy Avery <cavery@...hat.com>,
        Wanpeng Li <wanpeng.li@...mail.com>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v6 7/7] KVM: x86: hyperv: implement PV IPI send hypercalls

Paolo Bonzini <pbonzini@...hat.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