[PATCH v3 2/5] KVM: arm64: GICv3: Completely disable trapping on vcpu exit

[Marc Zyngier <maz@kernel.org>]

Fuad reports that on QEMU, the DIR trapping is still effective after
a vcpu exit and that the host is running nVHE, resulting in a BUG()
(we only expect DIR to be trapped for the guest, and never the host).

As it turns out, this is an implementation-dependent behaviour, which
the architecture allows, but that seem to be relatively uncommon across
implementations.

Fix this by completely zeroing the ICH_HCR_EL2 register when the
vcpu exits.

Reported-by: Fuad Tabba <tabba@google.com>
Fixes: ca30799f7c2d0 ("KVM: arm64: Turn vgic-v3 errata traps into a patched-in constant")
Closes: https://lore.kernel.org/r/CA+EHjTzRwswNq+hZQDD5tXj+-0nr04OmR201mHmi82FJ0VHuJA@mail.gmail.com
Signed-off-by: Marc Zyngier <maz@kernel.org>
---
 arch/arm64/kvm/hyp/vgic-v3-sr.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/arm64/kvm/hyp/vgic-v3-sr.c b/arch/arm64/kvm/hyp/vgic-v3-sr.c
index e950efa225478..71199e1a92940 100644
--- a/arch/arm64/kvm/hyp/vgic-v3-sr.c
+++ b/arch/arm64/kvm/hyp/vgic-v3-sr.c
@@ -243,7 +243,7 @@ void __vgic_v3_save_state(struct vgic_v3_cpu_if *cpu_if)
 		cpu_if->vgic_hcr |= val & ICH_HCR_EL2_EOIcount;
 	}
 
-	write_gicreg(compute_ich_hcr(cpu_if) & ~ICH_HCR_EL2_En, ICH_HCR_EL2);
+	write_gicreg(0, ICH_HCR_EL2);
 }
 
 void __vgic_v3_restore_state(struct vgic_v3_cpu_if *cpu_if)
-- 
2.47.3