From a057001e9e446f2195c34bc55c57e5cf353c99d6 Mon Sep 17 00:00:00 2001 From: Marc Zyngier Date: Wed, 25 May 2016 15:26:38 +0100 Subject: [PATCH] arm64: KVM: vgic-v3: Prevent the guest from messing with ICC_SRE_EL1 Both our GIC emulations are "strict", in the sense that we either emulate a GICv2 or a GICv3, and not a GICv3 with GICv2 legacy support. But when running on a GICv3 host, we still allow the guest to tinker with the ICC_SRE_EL1 register during its time slice: it can switch SRE off, observe that it is off, and yet on the next world switch, find the SRE bit to be set again. Not very nice. An obvious solution is to always trap accesses to ICC_SRE_EL1 (by clearing ICC_SRE_EL2.Enable), and to let the handler return the programmed value on a read, or ignore the write. That way, the guest can always observe that our GICv3 is SRE==1 only. Reviewed-by: Christoffer Dall Signed-off-by: Marc Zyngier Signed-off-by: Christoffer Dall --- arch/arm64/kvm/hyp/vgic-v3-sr.c | 6 ++---- 1 file changed, 2 insertions(+), 4 deletions(-) diff --git a/arch/arm64/kvm/hyp/vgic-v3-sr.c b/arch/arm64/kvm/hyp/vgic-v3-sr.c index 3129df9d3a73..40c3b4c3d125 100644 --- a/arch/arm64/kvm/hyp/vgic-v3-sr.c +++ b/arch/arm64/kvm/hyp/vgic-v3-sr.c @@ -313,10 +313,8 @@ void __hyp_text __vgic_v3_restore_state(struct kvm_vcpu *vcpu) * Prevent the guest from touching the GIC system registers if * SRE isn't enabled for GICv3 emulation. */ - if (!cpu_if->vgic_sre) { - write_gicreg(read_gicreg(ICC_SRE_EL2) & ~ICC_SRE_EL2_ENABLE, - ICC_SRE_EL2); - } + write_gicreg(read_gicreg(ICC_SRE_EL2) & ~ICC_SRE_EL2_ENABLE, + ICC_SRE_EL2); } void __hyp_text __vgic_v3_init_lrs(void) -- 2.20.1