[PATCH v1 2/4] KVM: s390: vsie: Disable some bits when in ESA mode

Eric Farman
2026-04-01T02:09:28Z

In the event that a nested guest is put in ESA mode,
ensure that some bits are scrubbed from the shadow SCB.

Signed-off-by: Eric Farman <farman@linux.ibm.com>
---
arch/s390/kvm/vsie.c | 14 ++++++++++++++
1 file changed, 14 insertions(+)

diff --git a/arch/s390/kvm/vsie.c b/arch/s390/kvm/vsie.c
index 888370a02ef7..584fc7803632 100644
--- a/arch/s390/kvm/vsie.c
+++ b/arch/s390/kvm/vsie.c
@@ -387,6 +387,17 @@ static int shadow_crycb(struct kvm_vcpu *vcpu, struct vsie_page *vsie_page)
return 0;
}

+static void shadow_esa(struct kvm_vcpu *vcpu, struct vsie_page *vsie_page)
+{
+ struct kvm_s390_sie_block *scb_s = &vsie_page->scb_s;
+
+ /* Ensure these bits are indeed turned off */
+ scb_s->eca &= ~ECA_VX;
+ scb_s->ecb &= ~ECB_GS;
+ scb_s->ecb3 &= ~ECB3_RI;
+ scb_s->ecd &= ~ECD_HOSTREGMGMT;
+}
+
/* shadow (round up/down) the ibc to avoid validity icpt */
static void prepare_ibc(struct kvm_vcpu *vcpu, struct vsie_page *vsie_page)
{
@@ -590,6 +601,9 @@ static int shadow_scb(struct kvm_vcpu *vcpu, struct vsie_page *vsie_page)
scb_s->hpid = HPID_VSIE;
scb_s->cpnc = scb_o->cpnc;

+ if (!(atomic_read(&scb_s->cpuflags) & CPUSTAT_ZARCH))
+ shadow_esa(vcpu, vsie_page);
+
prepare_ibc(vcpu, vsie_page);
rc = shadow_crycb(vcpu, vsie_page);
out:
--
2.51.0