KVM: arm64: Flush HCR_EL2.VSE to deliver SErrors to pKVM guests

KVM: arm64: Flush HCR_EL2.VSE to deliver SErrors to pKVM guests

With pKVM enabled, the host injects a virtual SError by setting
HCR_EL2.VSE on its vCPU copy, but flush_hyp_vcpu() only flows TWI/TWE
into the hyp vCPU that runs, so VSE never reaches it and a deferred
(masked) SError is never delivered. VSE is a host-owned injection
control, not a trap-configuration bit, so restricting the host's
trap-register values should not have dropped it.

Flow it on entry; sync_hyp_vcpu() already copies hcr_el2 back, so
delivery is reflected to the host. THis makes it consistent with
the existing forwarding of VSESR_EL2, which qualifies the Serror.

Fixes: b56680de9c648 ("KVM: arm64: Initialize trap register values in hyp in pKVM")
Reported-by: Sashiko (local):gemini-3.1-pro
Signed-off-by: Fuad Tabba <tabba@google.com>
Reviewed-by: Oliver Upton <oupton@kernel.org>
Link: https://patch.msgid.link/20260531154548.1505799-1-tabba@google.com
Signed-off-by: Marc Zyngier <maz@kernel.org>