[PATCH 1/2] KVM: arm64: Sync HCR_EL2.VSE back to the host vCPU under pKVM

[Fuad Tabba <fuad.tabba@linux.dev>]

flush_hyp_vcpu() copies HCR_EL2.VSE from the host vCPU into the hyp
vCPU on every entry, and nothing copies it back. Once the guest takes
the vSError the hyp vCPU's copy clears with the hardware bit while the
host's stays set, so the next entry pends the same SError again,
KVM_GET_VCPU_EVENTS keeps reporting it, and kvm_arch_vcpu_runnable()
never lets the vCPU block in WFI.

Reflect VSE back on every exit, which the flush-side comment already
promises.

Fixes: 734dc8c01c838 ("KVM: arm64: Implement lazy vCPU state sync for non-protected guests")
Signed-off-by: Fuad Tabba <fuad.tabba@linux.dev>
---
 arch/arm64/kvm/hyp/nvhe/hyp-main.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/arch/arm64/kvm/hyp/nvhe/hyp-main.c b/arch/arm64/kvm/hyp/nvhe/hyp-main.c
index 65a7c735aa398..be35ff5958c82 100644
--- a/arch/arm64/kvm/hyp/nvhe/hyp-main.c
+++ b/arch/arm64/kvm/hyp/nvhe/hyp-main.c
@@ -276,6 +276,10 @@ static void sync_hyp_vcpu(struct pkvm_hyp_vcpu *hyp_vcpu)
 
 	host_vcpu->arch.iflags		= hyp_vcpu->vcpu.arch.iflags;
 
+	/* Cleared by hardware once the guest takes the vSError. */
+	host_vcpu->arch.hcr_el2 &= ~HCR_VSE;
+	host_vcpu->arch.hcr_el2 |= hyp_vcpu->vcpu.arch.hcr_el2 & HCR_VSE;
+
 	sync_hyp_vgic_state(hyp_vcpu);
 }
 

base-commit: aa8e5dc6a7a2a1141ab40706a51010adcd0e57d2
-- 
2.39.5