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Tue, 19 May 2020 13:47:50 +0000 (UTC) Date: Tue, 19 May 2020 15:47:38 +0200 From: Cornelia Huck To: Janosch Frank Subject: Re: [PATCH v2 6/8] s390/sclp: add extended-length sccb support for kvm guest Message-ID: <20200519154739.0cd48192.cohuck@redhat.com> In-Reply-To: References: <20200515222032.18838-1-walling@linux.ibm.com> <20200515222032.18838-7-walling@linux.ibm.com> Organization: Red Hat GmbH MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.79 on 10.5.11.15 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: multipart/signed; boundary="Sig_/+BTsv7=p11yznsl7hpVUNDx"; protocol="application/pgp-signature"; micalg=pgp-sha256 Received-SPF: pass client-ip=207.211.31.81; envelope-from=cohuck@redhat.com; helo=us-smtp-delivery-1.mimecast.com X-detected-operating-system: by eggs.gnu.org: First seen = 2020/05/19 00:34:39 X-ACL-Warn: Detected OS = Linux 2.2.x-3.x [generic] [fuzzy] X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=0.001, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H4=0.001, RCVD_IN_MSPIKE_WL=0.001, SPF_PASS=-0.001 autolearn=_AUTOLEARN 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: Collin Walling , mst@redhat.com, david@redhat.com, qemu-devel@nongnu.org, pasic@linux.ibm.com, borntraeger@de.ibm.com, qemu-s390x@nongnu.org, svens@linux.ibm.com, thuth@redhat.com, pbonzini@redhat.com, mihajlov@linux.ibm.com, rth@twiddle.net Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" --Sig_/+BTsv7=p11yznsl7hpVUNDx Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: quoted-printable On Mon, 18 May 2020 10:55:24 +0200 Janosch Frank wrote: > On 5/16/20 12:20 AM, Collin Walling wrote: > > As more features and facilities are added to the Read SCP Info (RSCPI) > > response, more space is required to store them. The space used to store > > these new features intrudes on the space originally used to store CPU > > entries. This means as more features and facilities are added to the > > RSCPI response, less space can be used to store CPU entries. > >=20 > > With the Extended-Length SCCB (ELS) facility, a KVM guest can execute > > the RSCPI command and determine if the SCCB is large enough to store a > > complete reponse. If it is not large enough, then the required length > > will be set in the SCCB header. > >=20 > > The caller of the SCLP command is responsible for creating a > > large-enough SCCB to store a complete response. Proper checking should > > be in place, and the caller should execute the command once-more with > > the large-enough SCCB. > >=20 > > This facility also enables an extended SCCB for the Read CPU Info > > (RCPUI) command. > >=20 > > When this facility is enabled, the boundary violation response cannot > > be a result from the RSCPI, RSCPI Forced, or RCPUI commands. > >=20 > > In order to tolerate kernels that do not yet have full support for this > > feature, a "fixed" offset to the start of the CPU Entries within the > > Read SCP Info struct is set to allow for the original 248 max entries > > when this feature is disabled. > >=20 > > Additionally, this is introduced as a CPU feature to protect the guest > > from migrating to a machine that does not support storing an extended > > SCCB. This could otherwise hinder the VM from being able to read all > > available CPU entries after migration (such as during re-ipl). > >=20 > > Signed-off-by: Collin Walling > > --- > > hw/s390x/sclp.c | 21 ++++++++++++++++++++- > > include/hw/s390x/sclp.h | 1 + > > target/s390x/cpu_features_def.inc.h | 1 + > > target/s390x/gen-features.c | 1 + > > target/s390x/kvm.c | 4 ++++ > > 5 files changed, 27 insertions(+), 1 deletion(-) > >=20 > > diff --git a/hw/s390x/sclp.c b/hw/s390x/sclp.c > > index 755f5f3fab..bde4c5420e 100644 > > --- a/hw/s390x/sclp.c > > +++ b/hw/s390x/sclp.c > > @@ -56,6 +56,18 @@ static bool sccb_has_valid_boundary(uint64_t sccb_ad= dr, uint32_t code, > > uint64_t allowed_len =3D (sccb_addr & PAGE_MASK) + PAGE_SIZE; > > =20 > > switch (code & SCLP_CMD_CODE_MASK) { > > + case SCLP_CMDW_READ_SCP_INFO: > > + case SCLP_CMDW_READ_SCP_INFO_FORCED: > > + case SCLP_CMDW_READ_CPU_INFO: > > + /* > > + * An extended-length SCCB is only allowed for RSCPI and RSCPU= and is Nit: I had to stare at this for a bit before I figured out what the acronyms refer to. > > + * allowed to exceed the 4k boundary. The respective commands = will > > + * set the length field to the required length if an insuffici= ent > > + * SCCB length is provided. > > + */ > > + if (s390_has_feat(S390_FEAT_EXTENDED_LENGTH_SCCB)) { > > + return true; > > + } > > default: > > if (current_len <=3D allowed_len) { > > return true; (...) > > diff --git a/target/s390x/gen-features.c b/target/s390x/gen-features.c > > index 8ddeebc544..6857f657fb 100644 > > --- a/target/s390x/gen-features.c > > +++ b/target/s390x/gen-features.c > > @@ -522,6 +522,7 @@ static uint16_t full_GEN12_GA1[] =3D { > > S390_FEAT_AP_QUEUE_INTERRUPT_CONTROL, > > S390_FEAT_AP_FACILITIES_TEST, > > S390_FEAT_AP, > > + S390_FEAT_EXTENDED_LENGTH_SCCB, > > }; > > =20 > > static uint16_t full_GEN12_GA2[] =3D { > > diff --git a/target/s390x/kvm.c b/target/s390x/kvm.c > > index 69881a0da0..380fb81822 100644 > > --- a/target/s390x/kvm.c > > +++ b/target/s390x/kvm.c > > @@ -2456,6 +2456,10 @@ void kvm_s390_get_host_cpu_model(S390CPUModel *m= odel, Error **errp) > > KVM_S390_VM_CRYPTO_ENABLE_APIE)) { > > set_bit(S390_FEAT_AP, model->features); > > } > > + > > + /* Extended-Length SCCB is handled entirely within QEMU */ > > + set_bit(S390_FEAT_EXTENDED_LENGTH_SCCB, model->features); > > + =20 >=20 > We need to fence this for secure guests as the SIDA is only 4k at the > moment. >=20 > Do we need to take extra steps for migration safety? > I guess this is only available with host-passthrough or -model? What do you mean with '-model'? I think it can be added manually everywhere? But I'm always a bit confused by cpu models. >=20 > > /* strip of features that are not part of the maximum model */ > > bitmap_and(model->features, model->features, model->def->full_feat= , > > S390_FEAT_MAX); > > =20 >=20 >=20 --Sig_/+BTsv7=p11yznsl7hpVUNDx Content-Type: application/pgp-signature Content-Description: OpenPGP digital signature -----BEGIN PGP SIGNATURE----- iQIzBAEBCAAdFiEEw9DWbcNiT/aowBjO3s9rk8bwL68FAl7D43sACgkQ3s9rk8bw L69LTw/+LR9+ujJTuWh0vtYN+HBDUjbVF78aFgv0KiL1XOViEPDSAaPAgOvEJS70 ucJB+3Z5U2W4m8tCKax6cUQELuZ088z6ZeAltXUFzI7aifBD9fOMAAljqK6ACgyv DnZ8JME0y8fE2kj07VBAtsek/GGrLZwYRfe9lTVsPttYNAn36LfcCtmkN73wwLnV lT+lfmwgaFldZNZk5SiAQrEAn6Ywfk0gJ5YVXKpoYQO99e3N9sGdv0HHVNDeA81Y CWyAwuRZf/0SwF0Rf4nGWPdE4awQcgaA1fCfiaNZyM5UofFhQCWrhCQRKhhfIm8z sI2gahaSgAGKbZVe5LRBbjc3zXHconVJmuolfd8Z6LWAn/X8NfOtSBmX1JaBKv1W QOFLMX0B9Mrs6Nw4vCkoDBcujYk9P99hj7r/V9nrbXZmRYqwZklIviAOBAD+NlXX eXQpyQVUbG9oYnWxUToec8iQ3A8dE3vuFV1ZuK0AFy0v/8ooXtURgRMYP5pTxLff O4FFk+nhLRxr2WT93AIm2bbkWxnZWqMNPbShEK/6tgc7ioEOUa2PEuMb+xKz3gRs ydMqe502CsSkjkqKhNb1gRuKMz1OnrtUs4PcN5k51jC9I2E/vi/Bqu1DYaIvGuU9 0jFIVAQjs7DIdYtucTYxFQ6cgHY/duuTXstTjx6qVHSX27F2jbo= =Sw2j -----END PGP SIGNATURE----- --Sig_/+BTsv7=p11yznsl7hpVUNDx--