Re: [PATCH v11 3/3] KVM: s390: resetting the Topology-Change-Report
From: Pierre Morel
Date: Mon Jul 04 2022 - 09:54:26 EST
On 7/4/22 11:35, Janis Schoetterl-Glausch wrote:
On 7/1/22 18:25, Pierre Morel wrote:
During a subsystem reset the Topology-Change-Report is cleared.
Let's give userland the possibility to clear the MTCR in the case
of a subsystem reset.
To migrate the MTCR, we give userland the possibility to
query the MTCR state.
We indicate KVM support for the CPU topology facility with a new
KVM capability: KVM_CAP_S390_CPU_TOPOLOGY.
Signed-off-by: Pierre Morel <pmorel@xxxxxxxxxxxxx>
---
Documentation/virt/kvm/api.rst | 25 +++++++++++++++
arch/s390/include/uapi/asm/kvm.h | 10 ++++++
arch/s390/kvm/kvm-s390.c | 53 ++++++++++++++++++++++++++++++++
include/uapi/linux/kvm.h | 1 +
4 files changed, 89 insertions(+)
diff --git a/Documentation/virt/kvm/api.rst b/Documentation/virt/kvm/api.rst
index 11e00a46c610..5e086125d8ad 100644
--- a/Documentation/virt/kvm/api.rst
+++ b/Documentation/virt/kvm/api.rst
@@ -7956,6 +7956,31 @@ should adjust CPUID leaf 0xA to reflect that the PMU is disabled.
When enabled, KVM will exit to userspace with KVM_EXIT_SYSTEM_EVENT of
type KVM_SYSTEM_EVENT_SUSPEND to process the guest suspend request.
+8.37 KVM_CAP_S390_CPU_TOPOLOGY
+------------------------------
+
+:Capability: KVM_CAP_S390_CPU_TOPOLOGY
+:Architectures: s390
+:Type: vm
+
+This capability indicates that KVM will provide the S390 CPU Topology
+facility which consist of the interpretation of the PTF instruction for
+the function code 2 along with interception and forwarding of both the
+PTF instruction with function codes 0 or 1 and the STSI(15,1,x)
+instruction to the userland hypervisor.
The latter only if the user STSI capability is also enabled.
Hum, not sure about this.
we can not set facility 11 and return 3 to STSI(15) for valid selectors.
I think that it was right before, KVM_CAP_S390_CPU_TOPOLOGY and
KVM_CAP_S390_USER_STSI are independent in KVM, userland can turn on one
and not the other.
But KVM proposes both.
Of course it is stupid to turn on only KVM_CAP_S390_CPU_TOPOLOGY but KVM
is not responsible for this userland is.
Otherwise, we need to check on KVM_CAP_S390_USER_STSI before authorizing
KVM_CAP_S390_CPU_TOPOLOGY and that looks even more complicated for me,
or we suppress the KVM_CAP_S390_CPU_TOPOLOGY and implement the all
stsi(15) in the kernel what I really do not think is good because of the
complexity of the userland API
+
+The stfle facility 11, CPU Topology facility, should not be indicated
+to the guest without this capability.
+
+When this capability is present, KVM provides a new attribute group
+on vm fd, KVM_S390_VM_CPU_TOPOLOGY.
+This new attribute allows to get, set or clear the Modified Change
+Topology Report (MTCR) bit of the SCA through the kvm_device_attr
+structure.
+
+When getting the Modified Change Topology Report value, the attr->addr
+must point to a byte where the value will be stored.
+
9. Known KVM API problems
=========================
diff --git a/arch/s390/include/uapi/asm/kvm.h b/arch/s390/include/uapi/asm/kvm.h
index 7a6b14874d65..df5e8279ffd0 100644
--- a/arch/s390/include/uapi/asm/kvm.h
+++ b/arch/s390/include/uapi/asm/kvm.h
@@ -74,6 +74,7 @@ struct kvm_s390_io_adapter_req {
#define KVM_S390_VM_CRYPTO 2
#define KVM_S390_VM_CPU_MODEL 3
#define KVM_S390_VM_MIGRATION 4
+#define KVM_S390_VM_CPU_TOPOLOGY 5
/* kvm attributes for mem_ctrl */
#define KVM_S390_VM_MEM_ENABLE_CMMA 0
@@ -171,6 +172,15 @@ struct kvm_s390_vm_cpu_subfunc {
#define KVM_S390_VM_MIGRATION_START 1
#define KVM_S390_VM_MIGRATION_STATUS 2
+/* kvm attributes for cpu topology */
+#define KVM_S390_VM_CPU_TOPO_MTCR_CLEAR 0
+#define KVM_S390_VM_CPU_TOPO_MTCR_SET 1
+
+struct kvm_cpu_topology {
+ __u16 mtcr : 1;
+ __u16 reserved : 15;
+};
This is no longer used, is it?
No, I sent the wrong patch it seems!! Sorry for that.
There is nothing more in kvm.h now but the definition for
KVM_S390_VM_CPU_TOPOLOGY
+
/* for KVM_GET_REGS and KVM_SET_REGS */
struct kvm_regs {
/* general purpose regs for s390 */
diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c
index ee59b03f2e45..5029fe40adbd 100644
--- a/arch/s390/kvm/kvm-s390.c
+++ b/arch/s390/kvm/kvm-s390.c
@@ -606,6 +606,9 @@ int kvm_vm_ioctl_check_extension(struct kvm *kvm, long ext)
case KVM_CAP_S390_PROTECTED:
r = is_prot_virt_host();
break;
+ case KVM_CAP_S390_CPU_TOPOLOGY:
+ r = test_facility(11);
+ break;
default:
r = 0;
}
@@ -817,6 +820,20 @@ int kvm_vm_ioctl_enable_cap(struct kvm *kvm, struct kvm_enable_cap *cap)
icpt_operexc_on_all_vcpus(kvm);
r = 0;
break;
+ case KVM_CAP_S390_CPU_TOPOLOGY:
+ r = -EINVAL;
+ mutex_lock(&kvm->lock);
+ if (kvm->created_vcpus) {
+ r = -EBUSY;
+ } else if (test_facility(11)) {
+ set_kvm_facility(kvm->arch.model.fac_mask, 11);
+ set_kvm_facility(kvm->arch.model.fac_list, 11);
+ r = 0;
+ }
+ mutex_unlock(&kvm->lock);
+ VM_EVENT(kvm, 3, "ENABLE: CPU TOPOLOGY %s",
I still would go for consistency here, "ENABLE: CAP_S390_CPU_TOPOLOGY %s".
Yes, done.
+ r ? "(not available)" : "(success)");
+ break;
default:
r = -EINVAL;
break;
@@ -1716,6 +1733,33 @@ static void kvm_s390_update_topology_change_report(struct kvm *kvm, bool val)
read_unlock(&kvm->arch.sca_lock);
}
+static int kvm_s390_set_topology(struct kvm *kvm, struct kvm_device_attr *attr)
+{
+ if (!test_kvm_facility(kvm, 11))
+ return -ENXIO;
+
+ kvm_s390_update_topology_change_report(kvm, !!attr->attr);
Will this not be automatically clamped to 0,1 if the argument has type bool?
I do not know, anyway done like this is sure.
+ return 0;
+}
+
+static int kvm_s390_get_topology(struct kvm *kvm, struct kvm_device_attr *attr)
+{
+ union sca_utility utility;
+ struct bsca_block *sca = kvm->arch.sca;
+ __u8 topo;
+
+ if (!test_kvm_facility(kvm, 11))
+ return -ENXIO;
+
read_lock(&kvm->arch.sca_lock);
utility.val = READ_ONCE(kvm->arch.sca->utility.val);
read_unlock(&kvm->arch.sca_lock); >
And then get rid of the sca declaration.
OK
+ topo = utility.mtcr;
+
+ if (copy_to_user((void __user *)attr->addr, &topo, sizeof(topo)))
+ return -EFAULT;
+
+ return 0;
+}
+
[...]
--
Pierre Morel
IBM Lab Boeblingen