[PATCH v6 20/21] KVM: s390: vsie: Create minimal scb shadows for not running g3 blocks

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

Instead of creating a full shadow for vSIE control blocks only create a
minimal shadow for SIGP purposes for currently not running guest-3
control blocks. This reduces the overhead to shadow the whole guest-3
configuration.
The minimal shadow only contains the information needed for SIGPI and
SRSI. The shadow will still be recreated fully when a vSIE is entered
with that SCB later.

Signed-off-by: Christoph Schlameuss <schlameuss@linux.ibm.com>
---
 arch/s390/kvm/s390/vsie.c | 54 ++++++++++++++++++++++++++++++++---------------
 1 file changed, 37 insertions(+), 17 deletions(-)

diff --git a/arch/s390/kvm/s390/vsie.c b/arch/s390/kvm/s390/vsie.c
index f8dff6846fb3..67b68f4302b7 100644
--- a/arch/s390/kvm/s390/vsie.c
+++ b/arch/s390/kvm/s390/vsie.c
@@ -368,8 +368,7 @@ static void update_intervention_requests(struct vsie_page *vsie_page)
 static int prepare_cpuflags(struct kvm_vcpu *vcpu, struct vsie_page *vsie_page)
 {
 	struct kvm_s390_sie_block *scb_s = &vsie_page->scb_s;
-	struct kvm_s390_sie_block *scb_o = vsie_page->scb_o;
-	int newflags, cpuflags = atomic_read(&scb_o->cpuflags);
+	int newflags, cpuflags = atomic_read(&vsie_page->scb_o->cpuflags);
 
 	/* we don't allow ESA/390 guests unless explicitly enabled */
 	if (!(cpuflags & CPUSTAT_ZARCH) && !vcpu->kvm->arch.allow_vsie_esamode)
@@ -722,6 +721,39 @@ static void unshadow_scb(struct kvm_vcpu *vcpu, struct vsie_page *vsie_page)
 		scb_o->ihcpu = scb_s->ihcpu;
 }
 
+static int shadow_scb_minimal(struct kvm_vcpu *vcpu, struct vsie_page *vsie_page)
+{
+	struct kvm_s390_sie_block *scb_s = &vsie_page->scb_s;
+	struct kvm_s390_sie_block *scb_o = vsie_page->scb_o;
+	int rc;
+
+	/* make sure we don't have any leftovers when reusing the scb */
+	scb_s->icptcode = 0;
+	scb_s->eca = 0;
+	scb_s->ecb = 0;
+	scb_s->ecb2 = 0;
+	scb_s->ecb3 = 0;
+	scb_s->ecd = 0;
+	scb_s->fac = 0;
+	scb_s->fpf = 0;
+
+	rc = prepare_cpuflags(vcpu, vsie_page);
+	if (rc)
+		return rc;
+
+	scb_s->icpua = scb_o->icpua;
+	scb_s->ecb2 |= scb_o->ecb2 & ECB2_ESCA;
+
+	if (vsie_page->vsie_sca) {
+		scb_s->eca |= scb_o->eca & ECA_SIGPI;
+		scb_s->ecb |= scb_o->ecb & ECB_SRSI;
+		write_scao(scb_s, virt_to_phys(&vsie_page->vsie_sca->ssca));
+		scb_s->osda = virt_to_phys(scb_o);
+	}
+
+	return 0;
+}
+
 /*
  * Setup the shadow scb by copying and checking the relevant parts of the g2
  * provided scb.
@@ -741,17 +773,7 @@ static int shadow_scb(struct kvm_vcpu *vcpu, struct vsie_page *vsie_page)
 	unsigned long new_mso = 0;
 	int rc;
 
-	/* make sure we don't have any leftovers when reusing the scb */
-	scb_s->icptcode = 0;
-	scb_s->eca = 0;
-	scb_s->ecb = 0;
-	scb_s->ecb2 = 0;
-	scb_s->ecb3 = 0;
-	scb_s->ecd = 0;
-	scb_s->fac = 0;
-	scb_s->fpf = 0;
-
-	rc = prepare_cpuflags(vcpu, vsie_page);
+	rc = shadow_scb_minimal(vcpu, vsie_page);
 	if (rc)
 		goto out_validity;
 
@@ -781,8 +803,6 @@ static int shadow_scb(struct kvm_vcpu *vcpu, struct vsie_page *vsie_page)
 	if (!(atomic_read(&scb_s->cpuflags) & CPUSTAT_KSS))
 		scb_s->ictl |= ICTL_ISKE | ICTL_SSKE | ICTL_RRBE;
 
-	scb_s->icpua = scb_o->icpua;
-
 	if (!(atomic_read(&scb_s->cpuflags) & CPUSTAT_ZARCH))
 		new_prefix &= GUEST_PREFIX_MASK_ESA;
 	else
@@ -2182,7 +2202,7 @@ static int _shadow_sca_cpu(struct kvm_vcpu *vcpu, struct vsie_page *vsie_page,
 	if (rc)
 		return rc;
 
-	rc = shadow_scb(vcpu, vsie_page_n);
+	rc = shadow_scb_minimal(vcpu, vsie_page_n);
 	update_vsie_sca(vsie_sca, cpu_nr, vsie_page_n, sca_o_entry_hpa);
 	if (rc) {
 		/* copy intercept to primary scb_o, no unshadow_scb() on exit */
@@ -2209,7 +2229,7 @@ static int _shadow_sca(struct kvm_vcpu *vcpu, struct vsie_page *vsie_page,
 		clear_bit(VSIE_SCA_ESCA, &vsie_sca->flags);
 	sca_mcn_copy(vsie_sca, phys_to_virt(sca_o_hpa(vsie_sca)));
 
-	/* pin and make shadow for ALL scb in the sca */
+	/* pin and make minimal shadow for ALL scb in the sca */
 	cpu_slots = is_esca ? KVM_S390_MAX_VSIE_VCPUS : KVM_S390_BSCA_CPU_SLOTS;
 	for_each_set_bit_inv(cpu_nr, (unsigned long *)&vsie_sca->mcn, cpu_slots) {
 		rc = get_sca_entry_addr(vcpu->kvm, vsie_sca, cpu_nr, NULL, &sca_o_entry_hpa);

-- 
2.55.0