From c58513284029229842844929ddeaca44d013c128 Mon Sep 17 00:00:00 2001 From: Marc Zyngier Date: Wed, 25 May 2016 15:26:39 +0100 Subject: [PATCH] arm64: KVM: vgic-v3: Relax synchronization when SRE==1 The GICv3 backend of the vgic is quite barrier heavy, in order to ensure synchronization of the system registers and the memory mapped view for a potential GICv2 guest. But when the guest is using a GICv3 model, there is absolutely no need to execute all these heavy barriers, and it is actually beneficial to avoid them altogether. This patch makes the synchonization conditional, and ensures that we do not change the EL1 SRE settings if we do not need to. Reviewed-by: Christoffer Dall Signed-off-by: Marc Zyngier Signed-off-by: Christoffer Dall --- arch/arm64/kvm/hyp/vgic-v3-sr.c | 23 ++++++++++++++++------- 1 file changed, 16 insertions(+), 7 deletions(-) diff --git a/arch/arm64/kvm/hyp/vgic-v3-sr.c b/arch/arm64/kvm/hyp/vgic-v3-sr.c index 40c3b4c3d125..5f8f80b4a224 100644 --- a/arch/arm64/kvm/hyp/vgic-v3-sr.c +++ b/arch/arm64/kvm/hyp/vgic-v3-sr.c @@ -169,7 +169,8 @@ void __hyp_text __vgic_v3_save_state(struct kvm_vcpu *vcpu) * Make sure stores to the GIC via the memory mapped interface * are now visible to the system register interface. */ - dsb(st); + if (!cpu_if->vgic_sre) + dsb(st); cpu_if->vgic_vmcr = read_gicreg(ICH_VMCR_EL2); @@ -235,8 +236,12 @@ void __hyp_text __vgic_v3_save_state(struct kvm_vcpu *vcpu) val = read_gicreg(ICC_SRE_EL2); write_gicreg(val | ICC_SRE_EL2_ENABLE, ICC_SRE_EL2); - isb(); /* Make sure ENABLE is set at EL2 before setting SRE at EL1 */ - write_gicreg(1, ICC_SRE_EL1); + + if (!cpu_if->vgic_sre) { + /* Make sure ENABLE is set at EL2 before setting SRE at EL1 */ + isb(); + write_gicreg(1, ICC_SRE_EL1); + } } void __hyp_text __vgic_v3_restore_state(struct kvm_vcpu *vcpu) @@ -255,8 +260,10 @@ void __hyp_text __vgic_v3_restore_state(struct kvm_vcpu *vcpu) * been actually programmed with the value we want before * starting to mess with the rest of the GIC. */ - write_gicreg(cpu_if->vgic_sre, ICC_SRE_EL1); - isb(); + if (!cpu_if->vgic_sre) { + write_gicreg(0, ICC_SRE_EL1); + isb(); + } val = read_gicreg(ICH_VTR_EL2); max_lr_idx = vtr_to_max_lr_idx(val); @@ -305,8 +312,10 @@ void __hyp_text __vgic_v3_restore_state(struct kvm_vcpu *vcpu) * (re)distributors. This ensure the guest will read the * correct values from the memory-mapped interface. */ - isb(); - dsb(sy); + if (!cpu_if->vgic_sre) { + isb(); + dsb(sy); + } vcpu->arch.vgic_cpu.live_lrs = live_lrs; /*