From mboxrd@z Thu Jan  1 00:00:00 1970
From: Radim =?utf-8?B?S3LEjW3DocWZ?= <rkrcmar@redhat.com>
Subject: Re: [PATCH 3/5] KVM: add KVM_USER_EXIT vm ioctl for userspace exit
Date: Wed, 5 Aug 2015 15:34:43 +0200
Message-ID: <20150805133442.GA31952@potion.brq.redhat.com>
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Cc: linux-kernel@vger.kernel.org, kvm@vger.kernel.org
To: Paolo Bonzini <pbonzini@redhat.com>
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2015-08-05 15:29+0200, Paolo Bonzini:
> On 05/08/2015 15:21, Radim Kr=C4=8Dm=C3=A1=C5=99 wrote:
>> +	kvm_for_each_vcpu(idx, vcpu, kvm)
>> +		if (vcpu->vcpu_id =3D=3D vcpu_id) {
>> +			kvm_make_request(KVM_REQ_EXIT, vcpu);
>> +			kvm_vcpu_kick(vcpu);
>> +
>> +			return 0;
>> +		}
>> +
>=20
> Why not a vcpu ioctl?  kvm_for_each_vcpu can become pretty expensive =
if
> you have a few dozen VCPUs.

Yeah, it will be slow, the only bright side is low frequency of calls.

vcpu ioctl should only be issued by the vcpu thread so it would
significantly limit use.