linux-kernel - Re: [PATCH RESEND 2/3] KVM: Add paravirt remote TLB flush

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Message-ID: <93c53d82-2b62-bb74-c472-8923bb2893aa@redhat.com>
Date:   Thu, 9 Nov 2017 12:02:56 +0100
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     Wanpeng Li <kernellwp@...il.com>
Cc:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        kvm <kvm@...r.kernel.org>,
        Radim Krčmář <rkrcmar@...hat.com>,
        Wanpeng Li <wanpeng.li@...mail.com>,
        Eduardo Valentin <eduval@...zon.com>
Subject: Re: [PATCH RESEND 2/3] KVM: Add paravirt remote TLB flush

On 09/11/2017 12:01, Wanpeng Li wrote:
> 2017-11-09 18:48 GMT+08:00 Paolo Bonzini <pbonzini@...hat.com>:
>> On 09/11/2017 03:02, Wanpeng Li wrote:
>>> @@ -484,6 +511,8 @@ void __init kvm_guest_init(void)
>>>               pv_time_ops.steal_clock = kvm_steal_clock;
>>>       }
>>>
>>> +     pv_mmu_ops.flush_tlb_others = kvm_flush_tlb_others;
>>
>> This needs to be keyed on a new CPUID feature bit.  Eduardo is also
> 
> Will do.
> 
>> adding a new "PV_DEDICATED" hint and you might disable PV TLB flush when
>> PV_DEDICATED is set.
> 
> Why disable PV TLB flush for PV_DEDICATED(qspinlock)?

PV_DEDICATED says pretty much that it is very unlikely to have a
preempted vCPU.  Therefore, the cpumask loop is unnecessary.

Paolo