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KVM: s390: allow 255 VCPUs when sca entries aren't used

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If the SCA entries aren't used by the hardware (no SIGPIF), we
can simply not set the entries, stick to the basic sca and allow more
than 64 VCPUs.

To hinder any other facility from using these entries, let's properly
provoke intercepts by not setting the MCN and keeping the entries
unset.

This effectively allows when running KVM under KVM (vSIE) or under z/VM to
provide more than 64 VCPUs to a guest. Let's limit it to 255 for now, to
not run into problems if the CPU numbers are limited somewhere else.

Signed-off-by: David Hildenbrand <dahi@linux.vnet.ibm.com>
Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
This commit is contained in:
David Hildenbrand
2016-08-08 22:39:32 +02:00
committed by Christian Borntraeger
parent 80cd876338
commit a6940674c3
4 changed files with 32 additions and 2 deletions
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18
arch/s390/kvm/kvm-s390.c
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@@ -376,7 +376,9 @@ int kvm_vm_ioctl_check_extension(struct kvm *kvm, long ext)
case KVM_CAP_NR_VCPUS:
case KVM_CAP_MAX_VCPUS:
r = KVM_S390_BSCA_CPU_SLOTS;
if (sclp.has_esca && sclp.has_64bscao)
if (!kvm_s390_use_sca_entries())
r = KVM_MAX_VCPUS;
else if (sclp.has_esca && sclp.has_64bscao)
r = KVM_S390_ESCA_CPU_SLOTS;
break;
case KVM_CAP_NR_MEMSLOTS:
@@ -1553,6 +1555,8 @@ static int __kvm_ucontrol_vcpu_init(struct kvm_vcpu *vcpu)
static void sca_del_vcpu(struct kvm_vcpu *vcpu)
{
if (!kvm_s390_use_sca_entries())
return;
read_lock(&vcpu->kvm->arch.sca_lock);
if (vcpu->kvm->arch.use_esca) {
struct esca_block *sca = vcpu->kvm->arch.sca;
@@ -1570,6 +1574,13 @@ static void sca_del_vcpu(struct kvm_vcpu *vcpu)
static void sca_add_vcpu(struct kvm_vcpu *vcpu)
{
if (!kvm_s390_use_sca_entries()) {
struct bsca_block *sca = vcpu->kvm->arch.sca;
/* we still need the basic sca for the ipte control */
vcpu->arch.sie_block->scaoh = (__u32)(((__u64)sca) >> 32);
vcpu->arch.sie_block->scaol = (__u32)(__u64)sca;
}
read_lock(&vcpu->kvm->arch.sca_lock);
if (vcpu->kvm->arch.use_esca) {
struct esca_block *sca = vcpu->kvm->arch.sca;
@@ -1650,6 +1661,11 @@ static int sca_can_add_vcpu(struct kvm *kvm, unsigned int id)
{
int rc;
if (!kvm_s390_use_sca_entries()) {
if (id < KVM_MAX_VCPUS)
return true;
return false;
}
if (id < KVM_S390_BSCA_CPU_SLOTS)
return true;
if (!sclp.has_esca || !sclp.has_64bscao)