[PATCH RFC v2 08/11] KVM: s390: Allow guest-3 cpu add and remove with vsie sigpif

[Christoph Schlameuss <schlameuss@linux.ibm.com>]

As we are shadowing the SCA we need to add and remove the pointers to
the shadowed control blocks and sca entries whenever the mcn changes.

It is not expected that the mcn changes frequently for a already running
guest-3 configuration. So we can simply re-init the ssca whenever the
mcn changes.
To detect the mcn change we store the expected mcn in the struct
vsie_sca when running the ssca init.

Signed-off-by: Christoph Schlameuss <schlameuss@linux.ibm.com>
---
 arch/s390/kvm/vsie.c | 20 ++++++++++++++++++--
 1 file changed, 18 insertions(+), 2 deletions(-)

diff --git a/arch/s390/kvm/vsie.c b/arch/s390/kvm/vsie.c
index 72c794945be916cc107aba74e1609d3b4780d4b9..1e15220e1f1ecfd83b10aa0620ca84ff0ff3c1ac 100644
--- a/arch/s390/kvm/vsie.c
+++ b/arch/s390/kvm/vsie.c
@@ -1926,12 +1926,27 @@ static int init_ssca(struct kvm_vcpu *vcpu, struct vsie_page *vsie_page, struct
 	return PTR_ERR(vsie_page_n);
 }
 
+static bool sca_mcn_equals(struct vsie_sca *sca, u64 *mcn)
+{
+	bool is_esca = test_bit(VSIE_SCA_ESCA, &sca->flags);
+	int i;
+
+	if (!is_esca)
+		return ((struct bsca_block *)phys_to_virt(sca->ssca->osca))->mcn == *mcn;
+
+	for (i = 0; i < 4; i++)
+		if (((struct esca_block *)phys_to_virt(sca->ssca->osca))->mcn[i] != sca->mcn[i])
+			return false;
+	return true;
+}
+
 /*
  * Shadow the sca on vsie enter.
  */
 static int shadow_sca(struct kvm_vcpu *vcpu, struct vsie_page *vsie_page, struct vsie_sca *sca)
 {
 	struct kvm_s390_sie_block *scb_s = &vsie_page->scb_s;
+	bool do_init_ssca;
 	int rc;
 
 	vsie_page->sca = sca;
@@ -1947,8 +1962,9 @@ static int shadow_sca(struct kvm_vcpu *vcpu, struct vsie_page *vsie_page, struct
 	if (!use_vsie_sigpif_for(vcpu->kvm, vsie_page))
 		return false;
 
-	/* skip if the guest does not have an usable sca */
-	if (!sca->ssca->osca) {
+	do_init_ssca = !sca->ssca->osca;
+	do_init_ssca = do_init_ssca || !sca_mcn_equals(sca, sca->mcn);
+	if (do_init_ssca) {
 		rc = init_ssca(vcpu, vsie_page, sca);
 		if (rc)
 			return rc;

-- 
2.51.1