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

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Message-ID: <d92255fb-d876-1c7f-3ac3-123c417aa685@redhat.com>
Date:   Mon, 1 Oct 2018 18:21:34 +0200
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     Vitaly Kuznetsov <vkuznets@...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

On 01/10/2018 18:20, Vitaly Kuznetsov wrote:
> 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.

Just send follow ups now, please.  I already have enough long queue. :)

Paolo