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

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>

1 files changed, 4 insertions, 0 deletions

diff --git a/arch/s390/kvm/interrupt.c b/arch/s390/kvm/interrupt.c
index 353e0b78e667..be4db07f70d3 100644
--- a/arch/s390/kvm/interrupt.c
+++ b/arch/s390/kvm/interrupt.c
@@ -42,6 +42,7 @@ static int sca_ext_call_pending(struct kvm_vcpu *vcpu, int *src_id)
         if (!(atomic_read(&vcpu->arch.sie_block->cpuflags) & CPUSTAT_ECALL_PEND))
                 return 0;
 
+        BUG_ON(!kvm_s390_use_sca_entries());
         read_lock(&vcpu->kvm->arch.sca_lock);
         if (vcpu->kvm->arch.use_esca) {
                 struct esca_block *sca = vcpu->kvm->arch.sca;
@@ -70,6 +71,7 @@ static int sca_inject_ext_call(struct kvm_vcpu *vcpu, int src_id)
 {
         int expect, rc;
 
+        BUG_ON(!kvm_s390_use_sca_entries());
         read_lock(&vcpu->kvm->arch.sca_lock);
         if (vcpu->kvm->arch.use_esca) {
                 struct esca_block *sca = vcpu->kvm->arch.sca;
@@ -111,6 +113,8 @@ static void sca_clear_ext_call(struct kvm_vcpu *vcpu)
         struct kvm_s390_local_interrupt *li = &vcpu->arch.local_int;
         int rc, expect;
 
+        if (!kvm_s390_use_sca_entries())
+                return;
         atomic_andnot(CPUSTAT_ECALL_PEND, li->cpuflags);
         read_lock(&vcpu->kvm->arch.sca_lock);
         if (vcpu->kvm->arch.use_esca) {