On 9/6/21 8:37 PM, David Hildenbrand wrote:
On 03.08.21 10:26, Pierre Morel wrote:
We let the userland hypervisor know if the machine support the CPU
topology facility using a new KVM capability: KVM_CAP_S390_CPU_TOPOLOGY.
The PTF instruction will report a topology change if there is any change
with a previous STSI_15_2 SYSIB.
Changes inside a STSI_15_2 SYSIB occur if CPU bits are set or clear
inside the CPU Topology List Entry CPU mask field, which happens with
changes in CPU polarization, dedication, CPU types and adding or
removing CPUs in a socket.
The reporting to the guest is done using the Multiprocessor
Topology-Change-Report (MTCR) bit of the utility entry of the guest's
SCA which will be cleared during the interpretation of PTF.
To check if the topology has been modified we use a new field of the
arch vCPU to save the previous real CPU ID at the end of a schedule
and verify on next schedule that the CPU used is in the same socket.
We deliberatly ignore:
- polarization: only horizontal polarization is currently used in linux.
- CPU Type: only IFL Type are supported in Linux
- Dedication: we consider that only a complete dedicated CPU stack can
take benefit of the CPU Topology.
Signed-off-by: Pierre Morel <pmorel@xxxxxxxxxxxxx>
@@ -228,7 +232,7 @@ struct kvm_s390_sie_block {
__u8 icptcode; /* 0x0050 */
__u8 icptstatus; /* 0x0051 */
__u16 ihcpu; /* 0x0052 */
- __u8 reserved54; /* 0x0054 */
+ __u8 mtcr; /* 0x0054 */
#define IICTL_CODE_NONE 0x00
#define IICTL_CODE_MCHK 0x01
#define IICTL_CODE_EXT 0x02
@@ -246,6 +250,7 @@ struct kvm_s390_sie_block {
#define ECB_TE 0x10
#define ECB_SRSI 0x04
#define ECB_HOSTPROTINT 0x02
+#define ECB_PTF 0x01
From below I understand, that ECB_PTF can be used with stfl(11) in the
hypervisor.
What is to happen if the hypervisor doesn't support stfl(11) and we
consequently cannot use ECB_PTF? Will QEMU be able to emulate PTF fully?
__u8 ecb; /* 0x0061 */
#define ECB2_CMMA 0x80
#define ECB2_IEP 0x20
@@ -747,6 +752,7 @@ struct kvm_vcpu_arch {
bool skey_enabled;
struct kvm_s390_pv_vcpu pv;
union diag318_info diag318_info;
+ int prev_cpu;
};
struct kvm_vm_stat {
diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c
index b655a7d82bf0..ff6d8a2b511c 100644
--- a/arch/s390/kvm/kvm-s390.c
+++ b/arch/s390/kvm/kvm-s390.c
@@ -568,6 +568,7 @@ int kvm_vm_ioctl_check_extension(struct kvm *kvm,
long ext)
case KVM_CAP_S390_VCPU_RESETS:
case KVM_CAP_SET_GUEST_DEBUG:
case KVM_CAP_S390_DIAG318:
+ case KVM_CAP_S390_CPU_TOPOLOGY:
I would have expected instead
r = test_facility(11);
break
I will change to this as we decided not to support emulation if the hist
does not support facility 11.
...
r = 1;
break;
case KVM_CAP_SET_GUEST_DEBUG2:
@@ -819,6 +820,23 @@ 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:
+ mutex_lock(&kvm->lock);
+ if (kvm->created_vcpus) {
+ r = -EBUSY;
+ } else {
...
} 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;
} else {
r = -EINVAL;
}
similar to how we handle KVM_CAP_S390_VECTOR_REGISTERS.
But I assume you want to be able to support hosts without ECB_PTF, correct?
No more, after Christian comments we do not want to support emulation at
all.
...snip...
+
+ /* PTF needs both host and guest facilities to enable
interpretation */
+ if (test_kvm_facility(vcpu->kvm, 11) && test_facility(11))
+ vcpu->arch.sie_block->ecb |= ECB_PTF;
Here you say we need both ...
+
if (test_kvm_facility(vcpu->kvm, 73))
vcpu->arch.sie_block->ecb |= ECB_TE;
diff --git a/arch/s390/kvm/vsie.c b/arch/s390/kvm/vsie.c
index 4002a24bc43a..50d67190bf65 100644
--- a/arch/s390/kvm/vsie.c
+++ b/arch/s390/kvm/vsie.c
@@ -503,6 +503,9 @@ static int shadow_scb(struct kvm_vcpu *vcpu,
struct vsie_page *vsie_page)
/* Host-protection-interruption introduced with ESOP */
if (test_kvm_cpu_feat(vcpu->kvm, KVM_S390_VM_CPU_FEAT_ESOP))
scb_s->ecb |= scb_o->ecb & ECB_HOSTPROTINT;
+ /* CPU Topology */
+ if (test_kvm_facility(vcpu->kvm, 11))
+ scb_s->ecb |= scb_o->ecb & ECB_PTF;
but here you don't check?
do we really need to check at all, even for test_kvm_facility() ?
as facilities do not change during a guest session and we checked for
setting it at first time.
Regards,
Pierre
--
Pierre Morel
IBM Lab Boeblingen
