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authorMarc Zyngier <marc.zyngier@arm.com>2017-04-19 12:15:26 +0100
committerChristoffer Dall <cdall@linaro.org>2017-04-19 17:28:38 +0200
commitff567614d58551b650a2375b50be368fbfed5cd5 (patch)
tree0c94982d34a072e6654e177b1ce39522b4c6f6a6 /virt
parent6c7a5dce22b3f3cc44be098e2837fa6797edb8b8 (diff)
downloadlinux-ff567614d58551b650a2375b50be368fbfed5cd5.tar.bz2
KVM: arm/arm64: vgic-v3: De-optimize VMCR save/restore when emulating a GICv2
When emulating a GICv2-on-GICv3, special care must be taken to only save/restore VMCR_EL2 when ICC_SRE_EL1.SRE is cleared. Otherwise, all Group-0 interrupts end-up being delivered as FIQ, which is probably not what the guest expects, as demonstrated here with an unhappy EFI: FIQ Exception at 0x000000013BD21CC4 This means that we cannot perform the load/put trick when dealing with VMCR_EL2 (because the host has SRE set), and we have to deal with it in the world-switch. Fortunately, this is not the most common case (modern guests should be able to deal with GICv3 directly), and the performance is not worse than what it was before the VMCR optimization. Reviewed-by: Christoffer Dall <cdall@linaro.org> Signed-off-by: Marc Zyngier <marc.zyngier@arm.com> Signed-off-by: Christoffer Dall <cdall@linaro.org>
Diffstat (limited to 'virt')
-rw-r--r--virt/kvm/arm/hyp/vgic-v3-sr.c8
-rw-r--r--virt/kvm/arm/vgic/vgic-v3.c11
2 files changed, 15 insertions, 4 deletions
diff --git a/virt/kvm/arm/hyp/vgic-v3-sr.c b/virt/kvm/arm/hyp/vgic-v3-sr.c
index 3d0b1ddb6929..91922c1eddc8 100644
--- a/virt/kvm/arm/hyp/vgic-v3-sr.c
+++ b/virt/kvm/arm/hyp/vgic-v3-sr.c
@@ -128,8 +128,10 @@ 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.
*/
- if (!cpu_if->vgic_sre)
+ if (!cpu_if->vgic_sre) {
dsb(st);
+ cpu_if->vgic_vmcr = read_gicreg(ICH_VMCR_EL2);
+ }
if (used_lrs) {
int i;
@@ -205,11 +207,13 @@ void __hyp_text __vgic_v3_restore_state(struct kvm_vcpu *vcpu)
* delivered as a FIQ to the guest, with potentially fatal
* consequences. So we must make sure that ICC_SRE_EL1 has
* been actually programmed with the value we want before
- * starting to mess with the rest of the GIC.
+ * starting to mess with the rest of the GIC, and VMCR_EL2 in
+ * particular.
*/
if (!cpu_if->vgic_sre) {
write_gicreg(0, ICC_SRE_EL1);
isb();
+ write_gicreg(cpu_if->vgic_vmcr, ICH_VMCR_EL2);
}
val = read_gicreg(ICH_VTR_EL2);
diff --git a/virt/kvm/arm/vgic/vgic-v3.c b/virt/kvm/arm/vgic/vgic-v3.c
index bc7010db9f4d..df1503650300 100644
--- a/virt/kvm/arm/vgic/vgic-v3.c
+++ b/virt/kvm/arm/vgic/vgic-v3.c
@@ -373,12 +373,19 @@ void vgic_v3_load(struct kvm_vcpu *vcpu)
{
struct vgic_v3_cpu_if *cpu_if = &vcpu->arch.vgic_cpu.vgic_v3;
- kvm_call_hyp(__vgic_v3_write_vmcr, cpu_if->vgic_vmcr);
+ /*
+ * If dealing with a GICv2 emulation on GICv3, VMCR_EL2.VFIQen
+ * is dependent on ICC_SRE_EL1.SRE, and we have to perform the
+ * VMCR_EL2 save/restore in the world switch.
+ */
+ if (likely(cpu_if->vgic_sre))
+ kvm_call_hyp(__vgic_v3_write_vmcr, cpu_if->vgic_vmcr);
}
void vgic_v3_put(struct kvm_vcpu *vcpu)
{
struct vgic_v3_cpu_if *cpu_if = &vcpu->arch.vgic_cpu.vgic_v3;
- cpu_if->vgic_vmcr = kvm_call_hyp(__vgic_v3_read_vmcr);
+ if (likely(cpu_if->vgic_sre))
+ cpu_if->vgic_vmcr = kvm_call_hyp(__vgic_v3_read_vmcr);
}