Messages in this thread | | | Date | Mon, 4 Jul 2022 15:51:48 +0200 | Subject | Re: [PATCH v11 2/3] KVM: s390: guest support for topology function | From | Pierre Morel <> |
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On 7/4/22 13:17, Janosch Frank wrote: > On 7/4/22 13:02, Pierre Morel wrote: >> >> >> On 7/4/22 11:08, Janis Schoetterl-Glausch wrote: >>> On 7/1/22 18:25, 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 >>> s/he/it (twice) >>>> 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.And the user STSI capability. >>> Also: supportS. >>>> >>>> Signed-off-by: Pierre Morel <pmorel@linux.ibm.com> >>>> Reviewed-by: Nico Boehr <nrb@linux.ibm.com> >>>> --- >>>> arch/s390/include/asm/kvm_host.h | 18 +++++++++++++--- >>>> arch/s390/kvm/kvm-s390.c | 36 >>>> ++++++++++++++++++++++++++++++++ >>>> arch/s390/kvm/priv.c | 16 ++++++++++---- >>>> arch/s390/kvm/vsie.c | 8 +++++++ >>>> 4 files changed, 71 insertions(+), 7 deletions(-) >>>> >>>> diff --git a/arch/s390/include/asm/kvm_host.h >>>> b/arch/s390/include/asm/kvm_host.h >>>> index 766028d54a3e..ae6bd3d607de 100644 >>>> --- a/arch/s390/include/asm/kvm_host.h >>>> +++ b/arch/s390/include/asm/kvm_host.h >>>> @@ -93,19 +93,30 @@ union ipte_control { >>>> }; >>>> }; >>> [...] >>> >>>> diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c >>>> index 8fcb56141689..ee59b03f2e45 100644 >>>> --- a/arch/s390/kvm/kvm-s390.c >>>> +++ b/arch/s390/kvm/kvm-s390.c >>>> @@ -1691,6 +1691,31 @@ static int kvm_s390_get_cpu_model(struct kvm >>>> *kvm, struct kvm_device_attr *attr) >>>> return ret; >>>> } >>>> +/** >>>> + * kvm_s390_update_topology_change_report - update CPU topology >>>> change report >>>> + * @kvm: guest KVM description >>>> + * @val: set or clear the MTCR bit >>>> + * >>>> + * Updates the Multiprocessor Topology-Change-Report bit to signal >>>> + * the guest with a topology change. >>>> + * This is only relevant if the topology facility is present. >>>> + * >>>> + * The SCA version, bsca or esca, doesn't matter as offset is the >>>> same. >>>> + */ >>>> +static void kvm_s390_update_topology_change_report(struct kvm *kvm, >>>> bool val) >>>> +{ >>>> + struct bsca_block *sca = kvm->arch.sca; >>>> + union sca_utility new, old; >>>> + >>>> + read_lock(&kvm->arch.sca_lock); >>> >>> You forgot to put the assignment of sca under the lock. >> >> Should I really? >> What we want to protect here is the content of the sca. >> The sca itself does not change during the life of the KVM AFAIK. > > The SCA origin as well as the SCA contents can change within the > lifetime of a KVM VM. > > When we switch from bsca to esca we'll use new pages. > When we add/remove cpus we'll update the MCN and the CPU entry. > >
Oh! then Yes, right. thanks
-- Pierre Morel IBM Lab Boeblingen
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