On 5/12/22 11:31, David Hildenbrand wrote:
On 06.05.22 11:24, 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, let's give userland the possibility to
query the MTCR state.
Signed-off-by: Pierre Morel <pmorel@xxxxxxxxxxxxx>
---
arch/s390/include/uapi/asm/kvm.h | 5 ++
arch/s390/kvm/kvm-s390.c | 79 ++++++++++++++++++++++++++++++++
2 files changed, 84 insertions(+)
diff --git a/arch/s390/include/uapi/asm/kvm.h b/arch/s390/include/uapi/asm/kvm.h
index 7a6b14874d65..abdcf4069343 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 +172,10 @@ 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_MTR_CLEAR 0
+#define KVM_S390_VM_CPU_TOPO_MTR_SET 1
+
/* 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 c8bdce31464f..80a1244f0ead 100644
--- a/arch/s390/kvm/kvm-s390.c
+++ b/arch/s390/kvm/kvm-s390.c
@@ -1731,6 +1731,76 @@ static void kvm_s390_sca_set_mtcr(struct kvm *kvm)
ipte_unlock(kvm);
}
+/**
+ * kvm_s390_sca_clear_mtcr
+ * @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_clear_mtcr(struct kvm *kvm)
+{
+ struct bsca_block *sca = kvm->arch.sca; /* SCA version doesn't matter */
+
+ ipte_lock(kvm);
+ sca->utility &= ~SCA_UTILITY_MTCR;
One space too much.
sca->utility &= ~SCA_UTILITY_MTCR;
+ ipte_unlock(kvm);
+}
+
+static int kvm_s390_set_topology(struct kvm *kvm, struct kvm_device_attr *attr)
+{
+ if (!test_kvm_facility(kvm, 11))
+ return -ENXIO;
+
+ switch (attr->attr) {
+ case KVM_S390_VM_CPU_TOPO_MTR_SET:
+ kvm_s390_sca_set_mtcr(kvm);
+ break;
+ case KVM_S390_VM_CPU_TOPO_MTR_CLEAR:
+ kvm_s390_sca_clear_mtcr(kvm);
+ break;
+ }
+ return 0;
+}
+
+/**
+ * kvm_s390_sca_get_mtcr
+ * @kvm: guest KVM description
+ *
+ * Is only relevant if the topology facility is present,
+ * the caller should check KVM facility 11
+ *
+ * reports to QEMU the Multiprocessor Topology-Change-Report.
+ */
+static int kvm_s390_sca_get_mtcr(struct kvm *kvm)
+{
+ struct bsca_block *sca = kvm->arch.sca; /* SCA version doesn't matter */
+ int val;
+
+ ipte_lock(kvm);
+ val = !!(sca->utility & SCA_UTILITY_MTCR);
+ ipte_unlock(kvm);
+
+ return val;
+}
+
+static int kvm_s390_get_topology(struct kvm *kvm, struct kvm_device_attr *attr)
+{
+ int mtcr;
I think we prefer something like u16 when copying to user space.
I come back here.
I think I prefer to keep the int.
the u16 is more than the MTCR but the entire utility field, so what
should I do:
rename the function to kvm_s390_get_sca_utility() ?
and then should I modify the KVM_S390_VM_CPU_TOPOLOGY
to KVM_S390_VM_SCA_UTILITY ?
I do not like that, I do not think we should report/handle more
information than expected/needed.
I can mask the MTCR bit and return a u16 with bit 0 (0x8000) set
but I find this a little weird
I admit an int is may be not optimal.
logically I should report a bool but I do not like to report a bool
through the UAPI.
The more I think about it the more I think an int is OK.
Or in the case we want to spare memory space I can create a flag in a
u16 but it should theoretically be different than the firmware MTCR bit.
Could be 0x0001.
But still, it is only to leave during the copy_to_user where the copy of
an int may be as good or better than the copy of a u16.
So any more opinion on this?
Regards,
Pierre
+
+ if (!test_kvm_facility(kvm, 11))
+ return -ENXIO;
+
+ mtcr = kvm_s390_sca_get_mtcr(kvm);
+ if (copy_to_user((void __user *)attr->addr, &mtcr, sizeof(mtcr)))
+ return -EFAULT;
+
+ return 0;
+}
You should probably add documentation, and document that only the last
bit (0x1) has a meaning.
Apart from that LGTM.
--
Pierre Morel
IBM Lab Boeblingen
