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([2001:b07:6468:f312:a0f7:472a:1e7:7ef]) by smtp.gmail.com with ESMTPSA id a15sm14665669wrw.10.2019.11.11.05.49.36 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 11 Nov 2019 05:49:37 -0800 (PST) Subject: Re: [PATCH 2/5] KVM: add a check to ensure grow start value is nonzero To: Zhenzhong Duan , linux-kernel@vger.kernel.org Cc: kvm@vger.kernel.org, mtosatti@redhat.com, joao.m.martins@oracle.com, rafael.j.wysocki@intel.com, rkrcmar@redhat.com References: <1572060239-17401-1-git-send-email-zhenzhong.duan@oracle.com> <1572060239-17401-3-git-send-email-zhenzhong.duan@oracle.com> From: Paolo Bonzini Openpgp: preference=signencrypt Message-ID: <391dd11b-ebbb-28ff-5e57-4a795cd16a1b@redhat.com> Date: Mon, 11 Nov 2019 14:49:39 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.8.0 MIME-Version: 1.0 In-Reply-To: <1572060239-17401-3-git-send-email-zhenzhong.duan@oracle.com> Content-Language: en-US X-MC-Unique: y7uWyjZ9M6WyL0nf4keCAA-1 X-Mimecast-Spam-Score: 0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable Sender: kvm-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org On 26/10/19 05:23, Zhenzhong Duan wrote: > vcpu->halt_poll_ns could be zeroed in certain cases (e.g. by > halt_poll_ns_shrink). If halt_poll_ns_grow_start is zero, > vcpu->halt_poll_ns will never be larger than zero. >=20 > Signed-off-by: Zhenzhong Duan > --- > virt/kvm/kvm_main.c | 7 +++++++ > 1 file changed, 7 insertions(+) >=20 > diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c > index 2ca2979..1b6fe3b 100644 > --- a/virt/kvm/kvm_main.c > +++ b/virt/kvm/kvm_main.c > @@ -2266,6 +2266,13 @@ static void grow_halt_poll_ns(struct kvm_vcpu *vcp= u) > =09=09goto out; > =20 > =09val *=3D grow; > + > +=09/* > +=09 * vcpu->halt_poll_ns needs a nonzero start point to grow if it's zer= o. > +=09 */ > +=09if (!grow_start) > +=09=09grow_start =3D 1; > + > =09if (val < grow_start) > =09=09val =3D grow_start; > =20 >=20 Zeroing grow_start will simply disable halt polling. Is that a problem? Paolo