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Mon, 16 Aug 2021 14:37:34 -0700 (PDT) X-Google-Smtp-Source: ABdhPJwHYWyAOdj/MryChViS7gUkyVN3h9/TXgLiSXhqhFrAthsS5kfse8dW38PeNU1vNlIY9bISE4BeI1iG1igujr8= X-Received: by 2002:a65:5603:: with SMTP id l3mr110526pgs.281.1629149853876; Mon, 16 Aug 2021 14:37:33 -0700 (PDT) MIME-Version: 1.0 References: <20210816210603.42337-1-ehabkost@redhat.com> <20210816210603.42337-2-ehabkost@redhat.com> In-Reply-To: <20210816210603.42337-2-ehabkost@redhat.com> From: Paolo Bonzini Date: Mon, 16 Aug 2021 23:37:21 +0200 Message-ID: Subject: Re: [PULL 1/1] machine: Disallow specifying topology parameters as zero 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="00000000000053c2c305c9b402ae" Received-SPF: pass client-ip=216.205.24.124; envelope-from=pbonzini@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -34 X-Spam_score: -3.5 X-Spam_bar: --- X-Spam_report: (-3.5 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.698, 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_LOW=-0.7, RCVD_IN_MSPIKE_H2=-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: Peter Maydell , Andrew Jones , "Daniel P . Berrange" , Cornelia Huck , qemu-devel , Yanan Wang Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" --00000000000053c2c305c9b402ae Content-Type: text/plain; charset="UTF-8" How do we know that no one has ever used such configuration? The conversion was meant to be bug-compatible. Paolo Il lun 16 ago 2021, 23:06 Eduardo Habkost ha scritto: > From: Yanan Wang > > In the SMP configuration, we should either provide a topology > parameter with a reasonable value (greater than zero) or just > omit it and QEMU will compute the missing value. Users should > have never provided a configuration with parameters as zero > (e.g. -smp 8,sockets=0) which should be treated as invalid. > > But commit 1e63fe68580 (machine: pass QAPI struct to mc->smp_parse) > has added some doc which implied that 'anything=0' is valid and > has the same semantics as omitting a parameter. > > To avoid meaningless configurations possibly introduced by users > in the future and consequently a necessary deprecation process, > fix the doc and also add the corresponding sanity check. > > Fixes: 1e63fe68580 (machine: pass QAPI struct to mc->smp_parse) > Suggested-by: Andrew Jones > Signed-off-by: Yanan Wang > Reviewed-by: Daniel P. Berrange > Tested-by: Daniel P. Berrange > Reviewed-by: Andrew Jones > Reviewed-by: Cornelia Huck > Message-Id: <20210816024522.143124-2-wangyanan55@huawei.com> > Signed-off-by: Eduardo Habkost > --- > hw/core/machine.c | 14 ++++++++++++++ > qapi/machine.json | 6 +++--- > qemu-options.hx | 12 +++++++----- > 3 files changed, 24 insertions(+), 8 deletions(-) > > diff --git a/hw/core/machine.c b/hw/core/machine.c > index 54e040587dd..a7e119469aa 100644 > --- a/hw/core/machine.c > +++ b/hw/core/machine.c > @@ -832,6 +832,20 @@ static void machine_set_smp(Object *obj, Visitor *v, > const char *name, > return; > } > > + /* > + * A specified topology parameter must be greater than zero, > + * explicit configuration like "cpus=0" is not allowed. > + */ > + if ((config->has_cpus && config->cpus == 0) || > + (config->has_sockets && config->sockets == 0) || > + (config->has_dies && config->dies == 0) || > + (config->has_cores && config->cores == 0) || > + (config->has_threads && config->threads == 0) || > + (config->has_maxcpus && config->maxcpus == 0)) { > + error_setg(errp, "CPU topology parameters must be greater than > zero"); > + goto out_free; > + } > + > mc->smp_parse(ms, config, errp); > if (*errp) { > goto out_free; > diff --git a/qapi/machine.json b/qapi/machine.json > index c3210ee1fb2..9272cb3cf8b 100644 > --- a/qapi/machine.json > +++ b/qapi/machine.json > @@ -1288,8 +1288,8 @@ > ## > # @SMPConfiguration: > # > -# Schema for CPU topology configuration. "0" or a missing value lets > -# QEMU figure out a suitable value based on the ones that are provided. > +# Schema for CPU topology configuration. A missing value lets QEMU > +# figure out a suitable value based on the ones that are provided. > # > # @cpus: number of virtual CPUs in the virtual machine > # > @@ -1297,7 +1297,7 @@ > # > # @dies: number of dies per socket in the CPU topology > # > -# @cores: number of cores per thread in the CPU topology > +# @cores: number of cores per die in the CPU topology > # > # @threads: number of threads per core in the CPU topology > # > diff --git a/qemu-options.hx b/qemu-options.hx > index 83aa59a920f..aee622f577d 100644 > --- a/qemu-options.hx > +++ b/qemu-options.hx > @@ -227,11 +227,13 @@ SRST > of computing the CPU maximum count. > > Either the initial CPU count, or at least one of the topology > parameters > - must be specified. Values for any omitted parameters will be computed > - from those which are given. Historically preference was given to the > - coarsest topology parameters when computing missing values (ie sockets > - preferred over cores, which were preferred over threads), however, > this > - behaviour is considered liable to change. > + must be specified. The specified parameters must be greater than zero, > + explicit configuration like "cpus=0" is not allowed. Values for any > + omitted parameters will be computed from those which are given. > + Historically preference was given to the coarsest topology parameters > + when computing missing values (ie sockets preferred over cores, which > + were preferred over threads), however, this behaviour is considered > + liable to change. > ERST > > DEF("numa", HAS_ARG, QEMU_OPTION_numa, > -- > 2.31.1 > > --00000000000053c2c305c9b402ae Content-Type: text/html; charset="UTF-8" Content-Transfer-Encoding: quoted-printable
How do we know that no one has ever used such configurati= on? The conversion was meant to be bug-compatible.

Paolo

Il lun 16 ago 2021, 23:06 Eduardo Habkost &= lt;ehabkost@redhat.com> ha sc= ritto:
From: Yanan Wang <wan= gyanan55@huawei.com>

In the SMP configuration, we should either provide a topology
parameter with a reasonable value (greater than zero) or just
omit it and QEMU will compute the missing value. Users should
have never provided a configuration with parameters as zero
(e.g. -smp 8,sockets=3D0) which should be treated as invalid.

But commit 1e63fe68580 (machine: pass QAPI struct to mc->smp_parse)
has added some doc which implied that 'anything=3D0' is valid and has the same semantics as omitting a parameter.

To avoid meaningless configurations possibly introduced by users
in the future and consequently a necessary deprecation process,
fix the doc and also add the corresponding sanity check.

Fixes: 1e63fe68580 (machine: pass QAPI struct to mc->smp_parse)
Suggested-by: Andrew Jones <drjones@redhat.com>
Signed-off-by: Yanan Wang <wangyanan55@huawei.com>
Reviewed-by: Daniel P. Berrange <berrange@redhat.com>
Tested-by: Daniel P. Berrange <berrange@redhat.com>
Reviewed-by: Andrew Jones <drjones@redhat.com>
Reviewed-by: Cornelia Huck <cohuck@redhat.com>
Message-Id: <20210816024522.143124-2-wangyan= an55@huawei.com>
Signed-off-by: Eduardo Habkost <ehabkost@redhat.com>
---
=C2=A0hw/core/machine.c | 14 ++++++++++++++
=C2=A0qapi/machine.json |=C2=A0 6 +++---
=C2=A0qemu-options.hx=C2=A0 =C2=A0| 12 +++++++-----
=C2=A03 files changed, 24 insertions(+), 8 deletions(-)

diff --git a/hw/core/machine.c b/hw/core/machine.c
index 54e040587dd..a7e119469aa 100644
--- a/hw/core/machine.c
+++ b/hw/core/machine.c
@@ -832,6 +832,20 @@ static void machine_set_smp(Object *obj, Visitor *v, c= onst char *name,
=C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0return;
=C2=A0 =C2=A0 =C2=A0}

+=C2=A0 =C2=A0 /*
+=C2=A0 =C2=A0 =C2=A0* A specified topology parameter must be greater than = zero,
+=C2=A0 =C2=A0 =C2=A0* explicit configuration like "cpus=3D0" is = not allowed.
+=C2=A0 =C2=A0 =C2=A0*/
+=C2=A0 =C2=A0 if ((config->has_cpus && config->cpus =3D=3D 0= ) ||
+=C2=A0 =C2=A0 =C2=A0 =C2=A0 (config->has_sockets && config->= sockets =3D=3D 0) ||
+=C2=A0 =C2=A0 =C2=A0 =C2=A0 (config->has_dies && config->die= s =3D=3D 0) ||
+=C2=A0 =C2=A0 =C2=A0 =C2=A0 (config->has_cores && config->co= res =3D=3D 0) ||
+=C2=A0 =C2=A0 =C2=A0 =C2=A0 (config->has_threads && config->= threads =3D=3D 0) ||
+=C2=A0 =C2=A0 =C2=A0 =C2=A0 (config->has_maxcpus && config->= maxcpus =3D=3D 0)) {
+=C2=A0 =C2=A0 =C2=A0 =C2=A0 error_setg(errp, "CPU topology parameters= must be greater than zero");
+=C2=A0 =C2=A0 =C2=A0 =C2=A0 goto out_free;
+=C2=A0 =C2=A0 }
+
=C2=A0 =C2=A0 =C2=A0mc->smp_parse(ms, config, errp);
=C2=A0 =C2=A0 =C2=A0if (*errp) {
=C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0goto out_free;
diff --git a/qapi/machine.json b/qapi/machine.json
index c3210ee1fb2..9272cb3cf8b 100644
--- a/qapi/machine.json
+++ b/qapi/machine.json
@@ -1288,8 +1288,8 @@
=C2=A0##
=C2=A0# @SMPConfiguration:
=C2=A0#
-# Schema for CPU topology configuration.=C2=A0 "0" or a missing = value lets
-# QEMU figure out a suitable value based on the ones that are provided. +# Schema for CPU topology configuration. A missing value lets QEMU
+# figure out a suitable value based on the ones that are provided.
=C2=A0#
=C2=A0# @cpus: number of virtual CPUs in the virtual machine
=C2=A0#
@@ -1297,7 +1297,7 @@
=C2=A0#
=C2=A0# @dies: number of dies per socket in the CPU topology
=C2=A0#
-# @cores: number of cores per thread in the CPU topology
+# @cores: number of cores per die in the CPU topology
=C2=A0#
=C2=A0# @threads: number of threads per core in the CPU topology
=C2=A0#
diff --git a/qemu-options.hx b/qemu-options.hx
index 83aa59a920f..aee622f577d 100644
--- a/qemu-options.hx
+++ b/qemu-options.hx
@@ -227,11 +227,13 @@ SRST
=C2=A0 =C2=A0 =C2=A0of computing the CPU maximum count.

=C2=A0 =C2=A0 =C2=A0Either the initial CPU count, or at least one of the to= pology parameters
-=C2=A0 =C2=A0 must be specified. Values for any omitted parameters will be= computed
-=C2=A0 =C2=A0 from those which are given. Historically preference was give= n to the
-=C2=A0 =C2=A0 coarsest topology parameters when computing missing values (= ie sockets
-=C2=A0 =C2=A0 preferred over cores, which were preferred over threads), ho= wever, this
-=C2=A0 =C2=A0 behaviour is considered liable to change.
+=C2=A0 =C2=A0 must be specified. The specified parameters must be greater = than zero,
+=C2=A0 =C2=A0 explicit configuration like "cpus=3D0" is not allo= wed. Values for any
+=C2=A0 =C2=A0 omitted parameters will be computed from those which are giv= en.
+=C2=A0 =C2=A0 Historically preference was given to the coarsest topology p= arameters
+=C2=A0 =C2=A0 when computing missing values (ie sockets preferred over cor= es, which
+=C2=A0 =C2=A0 were preferred over threads), however, this behaviour is con= sidered
+=C2=A0 =C2=A0 liable to change.
=C2=A0ERST

=C2=A0DEF("numa", HAS_ARG, QEMU_OPTION_numa,
--
2.31.1

--00000000000053c2c305c9b402ae--