Messages in this thread | | | Date | Tue, 28 Jun 2022 12:58:06 +0200 | Subject | Re: [PATCH v10 2/3] KVM: s390: guest support for topology function | From | Pierre Morel <> |
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On 6/28/22 10:59, Janis Schoetterl-Glausch wrote: > On 6/20/22 14:54, Pierre Morel wrote: >> We report a topology change to the guest for any CPU hotplug. >> >> The reporting to the guest is done using the Multiprocessor >> Topology-Change-Report (MTCR) bit of the utility entry in the guest's >> SCA which will be cleared during the interpretation of PTF. >> >> On every vCPU creation we set the MCTR bit to let the guest know the >> next time he uses the PTF with command 2 instruction that the >> topology changed and that he should use the STSI(15.1.x) instruction >> to get the topology details. >> >> STSI(15.1.x) gives information on the CPU configuration topology. >> Let's accept the interception of STSI with the function code 15 and >> let the userland part of the hypervisor handle it when userland >> support the CPU Topology facility. >> >> Signed-off-by: Pierre Morel <pmorel@linux.ibm.com> >> --- >> arch/s390/include/asm/kvm_host.h | 11 ++++++++--- >> arch/s390/kvm/kvm-s390.c | 27 ++++++++++++++++++++++++++- >> arch/s390/kvm/priv.c | 15 +++++++++++---- >> arch/s390/kvm/vsie.c | 3 +++ >> 4 files changed, 48 insertions(+), 8 deletions(-) >> > [...] > >> diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c >> index 8fcb56141689..95b96019ca8e 100644 >> --- a/arch/s390/kvm/kvm-s390.c >> +++ b/arch/s390/kvm/kvm-s390.c >> @@ -1691,6 +1691,25 @@ static int kvm_s390_get_cpu_model(struct kvm *kvm, struct kvm_device_attr *attr) >> return ret; >> } >> >> +/** >> + * kvm_s390_sca_set_mtcr > > I wonder if there is a better name, kvm_s390_report_topology_change maybe? > >> + * @kvm: guest KVM description >> + * >> + * Is only relevant if the topology facility is present, >> + * the caller should check KVM facility 11 >> + * >> + * Updates the Multiprocessor Topology-Change-Report to signal >> + * the guest with a topology change. >> + */ >> +static void kvm_s390_sca_set_mtcr(struct kvm *kvm) >> +{ > > Do we need a sca_lock read_section here? If we don't why not? > Did not see one up the stack, but I might have overlooked something.
Yes we do. As I said about your well justified comment in a previous mail, ipte_lock is not the right thing to use here and I will replace with an inter locked update.
> >> + struct bsca_block *sca = kvm->arch.sca; /* SCA version doesn't matter */ >> + >> + ipte_lock(kvm); >> + sca->utility |= SCA_UTILITY_MTCR; >> + ipte_unlock(kvm); >> +} >> + > > [...] >
-- Pierre Morel IBM Lab Boeblingen
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