Messages in this thread | | | Date | Mon, 4 Jul 2022 13:02:16 +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 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.
> >> + do { >> + old = READ_ONCE(sca->utility); >> + new = old; >> + new.mtcr = val; >> + } while (cmpxchg(&sca->utility.val, old.val, new.val) != old.val); >> + read_unlock(&kvm->arch.sca_lock); >> +} >> + >> static int kvm_s390_vm_set_attr(struct kvm *kvm, struct kvm_device_attr *attr) >> { >> int ret; >> @@ -2877,6 +2902,7 @@ void kvm_arch_vcpu_destroy(struct kvm_vcpu *vcpu) >> kvm_clear_async_pf_completion_queue(vcpu); >> if (!kvm_is_ucontrol(vcpu->kvm)) >> sca_del_vcpu(vcpu); >> + kvm_s390_update_topology_change_report(vcpu->kvm, 1); >> >> if (kvm_is_ucontrol(vcpu->kvm)) >> gmap_remove(vcpu->arch.gmap); >> @@ -3272,6 +3298,14 @@ static int kvm_s390_vcpu_setup(struct kvm_vcpu *vcpu) >> vcpu->arch.sie_block->ecb |= ECB_HOSTPROTINT; >> if (test_kvm_facility(vcpu->kvm, 9)) >> vcpu->arch.sie_block->ecb |= ECB_SRSI; >> + /* >> + * CPU Topology >> + * This facility only uses the utility field of the SCA and none >> + * of the cpu entries that are problematic with the other >> + * interpretation facilities so we can pass it through. >> + */ > > This is the comment for vsie.c
right
>> + if (test_kvm_facility(vcpu->kvm, 11)) >> + vcpu->arch.sie_block->ecb |= ECB_PTF; >> if (test_kvm_facility(vcpu->kvm, 73)) >> vcpu->arch.sie_block->ecb |= ECB_TE; >> if (!kvm_is_ucontrol(vcpu->kvm)) >> @@ -3403,6 +3437,8 @@ int kvm_arch_vcpu_create(struct kvm_vcpu *vcpu) >> rc = kvm_s390_vcpu_setup(vcpu); >> if (rc) >> goto out_ucontrol_uninit; >> + >> + kvm_s390_update_topology_change_report(vcpu->kvm, 1); >> return 0; >> >> out_ucontrol_uninit: >> diff --git a/arch/s390/kvm/priv.c b/arch/s390/kvm/priv.c >> index 12c464c7cddf..046afee1be94 100644 >> --- a/arch/s390/kvm/priv.c >> +++ b/arch/s390/kvm/priv.c >> @@ -873,10 +873,13 @@ static int handle_stsi(struct kvm_vcpu *vcpu) >> if (vcpu->arch.sie_block->gpsw.mask & PSW_MASK_PSTATE) >> return kvm_s390_inject_program_int(vcpu, PGM_PRIVILEGED_OP); >> >> - if (fc > 3) { >> - kvm_s390_set_psw_cc(vcpu, 3); >> - return 0; >> - } >> + /* Bailout forbidden function codes */ >> + if (fc > 3 && (fc != 15 || kvm_s390_pv_cpu_is_protected(vcpu))) >> + goto out_no_data; >> + >> + /* fc 15 is provided with PTF/CPU topology support */ >> + if (fc == 15 && !test_kvm_facility(vcpu->kvm, 11)) >> + goto out_no_data; >> >> if (vcpu->run->s.regs.gprs[0] & 0x0fffff00 >> || vcpu->run->s.regs.gprs[1] & 0xffff0000) >> @@ -910,6 +913,11 @@ static int handle_stsi(struct kvm_vcpu *vcpu) >> goto out_no_data; >> handle_stsi_3_2_2(vcpu, (void *) mem); >> break; >> + case 15: /* fc 15 is fully handled in userspace */ >> + if (vcpu->kvm->arch.user_stsi) >> + insert_stsi_usr_data(vcpu, operand2, ar, fc, sel1, sel2); >> + trace_kvm_s390_handle_stsi(vcpu, fc, sel1, sel2, operand2); >> + return -EREMOTE; > > This doesn't look right to me, you still return -EREMOTE if user_stsi is false. > The way I read the PoP here is that it is ok to set condition code 3 for the else case
Yes it is what I wanted to do. I do not understand what I did here is stupid.
-- Pierre Morel IBM Lab Boeblingen
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