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Tue, 22 Sep 2020 12:50:01 -0700 (PDT) X-Google-Smtp-Source: ABdhPJw66bMeAspDMwVpjo8iSLAeRscANP5935AE9qB+u8kXBqNGXO4OfOu4ja7XivEHu53gPoDYQQVOtRC1/PdksXE= X-Received: by 2002:a17:906:868c:: with SMTP id g12mr6320725ejx.230.1600804201730; Tue, 22 Sep 2020 12:50:01 -0700 (PDT) MIME-Version: 1.0 References: <20200922151455.1763896-1-ehabkost@redhat.com> <87v9g5es9n.fsf@vitty.brq.redhat.com> <20200922161055.GY57321@habkost.net> <87pn6depau.fsf@vitty.brq.redhat.com> <20200922172229.GB57321@habkost.net> <20200922193903.GA2044576@habkost.net> In-Reply-To: <20200922193903.GA2044576@habkost.net> From: Paolo Bonzini Date: Tue, 22 Sep 2020 21:49:48 +0200 Message-ID: Subject: Re: [PATCH] i386: Don't try to set MSR_KVM_ASYNC_PF_EN if kernel-irqchip=off To: Eduardo Habkost Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=pbonzini@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: multipart/alternative; boundary="000000000000ccb2f805afec4556" Received-SPF: pass client-ip=216.205.24.124; envelope-from=pbonzini@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-detected-operating-system: by eggs.gnu.org: First seen = 2020/09/22 15:47:47 X-ACL-Warn: Detected OS = Linux 2.2.x-3.x [generic] [fuzzy] X-Spam_score_int: -35 X-Spam_score: -3.6 X-Spam_bar: --- X-Spam_report: (-3.6 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-1.455, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, HTML_MESSAGE=0.001, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H5=0.001, RCVD_IN_MSPIKE_WL=0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Laurent Vivier , 1896263@bugs.launchpad.net, kvm@vger.kernel.org, Marcelo Tosatti , qemu-devel , "Dr. David Alan Gilbert" , Stefan Hajnoczi , Vitaly Kuznetsov , Richard Henderson Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" --000000000000ccb2f805afec4556 Content-Type: text/plain; charset="UTF-8" Il mar 22 set 2020, 21:39 Eduardo Habkost ha scritto: > On Tue, Sep 22, 2020 at 07:26:42PM +0200, Paolo Bonzini wrote: > > On 22/09/20 19:22, Eduardo Habkost wrote: > > > If it was possible, did KVM break live migration of > > > kernel-irqchip=off guests that enabled APF? This would mean my > > > patch is replacing a crash with a silent migration bug. Not nice > > > either way. > > > > Let's drop kernel-irqchip=off completely so migration is not broken. :) > > > > I'm actually serious, I don't think we need a deprecation period even. > > I wasn't sure about this, but then I've noticed the man page says > "disabling the in-kernel irqchip completely is not recommended > except for debugging purposes." > > Does this note apply to all architectures? > At least on ARM, Raspberry Pi 4 cannot use kernel-irqchip=on at all. But remember I am only talking about x86. Paolo > -- > Eduardo > > --000000000000ccb2f805afec4556 Content-Type: text/html; charset="UTF-8" Content-Transfer-Encoding: quoted-printable


Il mar 22 set 2020, 21:39 Eduardo Habkost <ehabkost@redhat.com> ha scritto:
=
On Tue, Sep 22, 2020 at 07:26:42PM +02= 00, Paolo Bonzini wrote:
> On 22/09/20 19:22, Eduardo Habkost wrote:
> > If it was possible, did KVM break live migration of
> > kernel-irqchip=3Doff guests that enabled APF?=C2=A0 This would me= an my
> > patch is replacing a crash with a silent migration bug.=C2=A0 Not= nice
> > either way.
>
> Let's drop kernel-irqchip=3Doff completely so migration is not bro= ken. :)
>
> I'm actually serious, I don't think we need a deprecation peri= od even.

I wasn't sure about this, but then I've noticed the man page says "disabling the in-kernel irqchip completely is not recommended
except for debugging purposes."

Does this note apply to all architectures?

At least on ARM, Raspberry Pi 4 c= annot use kernel-irqchip=3Don at all. But remember I am only talking about = x86.

Paolo


--
Eduardo

--000000000000ccb2f805afec4556--