linux-kernel - Re: [PATCH] KVM: Pre-allocate 1 cpumask variable per cpu for both pv tlb and pv ipis

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Date:   Tue, 04 Feb 2020 15:42:04 +0100
From:   Vitaly Kuznetsov <vkuznets@...hat.com>
To:     Thadeu Lima de Souza Cascardo <cascardo@...onical.com>,
        Wanpeng Li <kernellwp@...il.com>
Cc:     LKML <linux-kernel@...r.kernel.org>, kvm <kvm@...r.kernel.org>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Sean Christopherson <sean.j.christopherson@...el.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Joerg Roedel <joro@...tes.org>
Subject: Re: [PATCH] KVM: Pre-allocate 1 cpumask variable per cpu for both pv tlb and pv ipis

Thadeu Lima de Souza Cascardo <cascardo@...onical.com> writes:

>> > >      /*
>> > > @@ -624,6 +625,7 @@ static void __init kvm_guest_init(void)
>> > >          kvm_para_has_feature(KVM_FEATURE_STEAL_TIME)) {
>> > >          pv_ops.mmu.flush_tlb_others = kvm_flush_tlb_others;
>> > >          pv_ops.mmu.tlb_remove_table = tlb_remove_table;
>> > > +        pr_info("KVM setup pv remote TLB flush\n");
>> > >      }
>> > >
>
> I am more concerned about printing the "KVM setup pv remote TLB flush" message,
> not only when KVM pv is used, but pv TLB flush is not going to be used, but
> also when the system is not even paravirtualized.

Huh? In Wanpeng's patch this print is under

	if (kvm_para_has_feature(KVM_FEATURE_PV_TLB_FLUSH) &&
	    !kvm_para_has_hint(KVM_HINTS_REALTIME) &&
	    kvm_para_has_feature(KVM_FEATURE_STEAL_TIME))

and if you mean another patch we descussed before which was adding
 (!kvm_para_available() || nopv) check than it's still needed. Or,
alternatively, we can make kvm_para_has_feature() check for that.

-- 
Vitaly