[PATCH] KVM: arm64: Filter out HCR_EL2.VSE when running in hypervisor context

[Marc Zyngier]

HCR_EL2.VSE is delivering a virtual SError to the guest, and does not
affect EL2 itself. However, when computing the host's HCR_EL2 value,
we take the guest's view of HCR_EL2.VSE at face value, and apply it
irrespective of the guest's exception level we are returning to.

The result is that a L1 hypervisor injecting a virtual SError to an L2
by setting its HCR_EL2.VSE to 1 results in itself getting the SError
as if it was a physical one if it traps for any reason before returning
to L2.

Fix it by filtering HCR_EL2.VSE out when entering the L1 host context.

Fixes: 04ab519bb86df ("KVM: arm64: nv: Configure HCR_EL2 for FEAT_NV2")
Signed-off-by: Marc Zyngier <maz at kernel.org>
Cc: stable at vger.kernel.org
---
 arch/arm64/kvm/hyp/vhe/switch.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/arch/arm64/kvm/hyp/vhe/switch.c b/arch/arm64/kvm/hyp/vhe/switch.c
index 477f1580ffeaa..eddda649d9ee1 100644
--- a/arch/arm64/kvm/hyp/vhe/switch.c
+++ b/arch/arm64/kvm/hyp/vhe/switch.c
@@ -68,6 +68,9 @@ static u64 __compute_hcr(struct kvm_vcpu *vcpu)
 		if (!vcpu_el2_e2h_is_set(vcpu))
 			hcr |= HCR_NV1;
 
+		/* Virtual SErrors only apply to L2, not L1 */
+		guest_hcr &= ~HCR_VSE;
+
 		write_sysreg_s(vcpu->arch.ctxt.vncr_array, SYS_VNCR_EL2);
 	} else {
 		host_data_clear_flag(VCPU_IN_HYP_CONTEXT);
-- 
2.39.2