Re: [PATCH v11 2/3] KVM: s390: guest support for topology function
From: Pierre Morel
Date: Mon Jul 04 2022 - 06:57:56 EST
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@xxxxxxxxxxxxx>
Reviewed-by: Nico Boehr <nrb@xxxxxxxxxxxxx>
---
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