From: Cornelia Huck <cohuck@redhat.com>
To: Collin Walling <walling@linux.ibm.com>
Cc: thuth@redhat.com, frankja@linux.ibm.com, 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, pbonzini@redhat.com, mihajlov@linux.ibm.com,
rth@twiddle.net
Subject: Re: [PATCH v4 6/8] s390/sclp: add extended-length sccb support for kvm guest
Date: Wed, 15 Jul 2020 18:05:48 +0200 [thread overview]
Message-ID: <20200715180548.5ce11fcc.cohuck@redhat.com> (raw)
In-Reply-To: <e04f99e1-8f9e-84f6-6aa6-fdae2f6088a9@linux.ibm.com>
On Wed, 15 Jul 2020 11:35:06 -0400
Collin Walling <walling@linux.ibm.com> wrote:
> On 6/26/20 6:01 AM, Cornelia Huck wrote:
> > On Wed, 24 Jun 2020 16:23:10 -0400
> > Collin Walling <walling@linux.ibm.com> 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.
> >>
> >> 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.
> >>
> >> 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.
> >>
> >> This facility also enables an extended SCCB for the Read CPU Info
> >> (RCPUI) command.
> >>
> >> When this facility is enabled, the boundary violation response cannot
> >> be a result from the RSCPI, RSCPI Forced, or RCPUI commands.
> >>
> >> 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.
> >>
> >> 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).
> >>
> >> Signed-off-by: Collin Walling <walling@linux.ibm.com>
> >> ---
> >> hw/s390x/sclp.c | 24 +++++++++++++++++++++++-
> >> include/hw/s390x/sclp.h | 1 +
> >> target/s390x/cpu_features_def.inc.h | 1 +
> >> target/s390x/gen-features.c | 1 +
> >> target/s390x/kvm.c | 8 ++++++++
> >> 5 files changed, 34 insertions(+), 1 deletion(-)
> >>
> >
> > (...)
> >
> >> @@ -111,6 +131,8 @@ static void read_SCP_info(SCLPDevice *sclp, SCCB *sccb)
> >> CPUEntry *entries_start = (void *)sccb + offset_cpu;
> >>
> >> if (!sccb_verify_length(sccb, machine->possible_cpus->len, offset_cpu)) {
> >> + qemu_log_mask(LOG_GUEST_ERROR, "insufficient sccb size to store "
> >> + "read scp info response\n");
> >
> > Not sure if logging needed/provided length would be helpful here.
> >
>
> I had the thought that it may be beneficial for kernel development -- it
> gives a response if an SCCB size needs to be larger.
If we have the info, we might as well log it, I guess.
next prev parent reply other threads:[~2020-07-15 16:07 UTC|newest]
Thread overview: 32+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-06-24 20:23 [PATCH v4 0/8] s390: Extended-Length SCCB & DIAGNOSE 0x318 Collin Walling
2020-06-24 20:23 ` [PATCH v4 1/8] s390/sclp: get machine once during read scp/cpu info Collin Walling
2020-06-24 20:23 ` [PATCH v4 2/8] s390/sclp: check sccb len before filling in data Collin Walling
2020-06-24 20:23 ` [PATCH v4 3/8] s390/sclp: rework sclp boundary and length checks Collin Walling
2020-06-25 6:29 ` Thomas Huth
2020-07-20 8:17 ` David Hildenbrand
2020-07-20 20:06 ` Collin Walling
2020-07-21 8:41 ` David Hildenbrand
2020-07-21 18:40 ` Collin Walling
2020-07-23 6:26 ` Cornelia Huck
2020-07-24 15:06 ` Collin Walling
2020-06-24 20:23 ` [PATCH v4 4/8] s390/sclp: read sccb from mem based on sccb length Collin Walling
2020-07-20 8:19 ` David Hildenbrand
2020-07-20 20:06 ` Collin Walling
2020-06-24 20:23 ` [PATCH v4 5/8] s390/sclp: use cpu offset to locate cpu entries Collin Walling
2020-06-24 20:23 ` [PATCH v4 6/8] s390/sclp: add extended-length sccb support for kvm guest Collin Walling
2020-06-26 10:01 ` Cornelia Huck
2020-07-15 15:35 ` Collin Walling
2020-07-15 16:05 ` Cornelia Huck [this message]
2020-06-24 20:23 ` [PATCH v4 7/8] s390/kvm: header sync for diag318 Collin Walling
2020-06-24 20:23 ` [PATCH v4 8/8] s390: guest support for diagnose 0x318 Collin Walling
2020-06-26 10:03 ` Cornelia Huck
2020-07-15 15:36 ` [PATCH v4 0/8] s390: Extended-Length SCCB & DIAGNOSE 0x318 Collin Walling
2020-07-15 16:04 ` Cornelia Huck
2020-07-15 16:26 ` Collin Walling
2020-07-16 12:02 ` Cornelia Huck
2020-09-09 7:54 ` Christian Borntraeger
2020-09-09 8:46 ` Cornelia Huck
2020-09-09 9:43 ` Cornelia Huck
2020-09-09 18:13 ` Collin Walling
2020-09-10 6:38 ` Cornelia Huck
2020-09-10 6:49 ` Collin Walling
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