[RFC 22/55] KVM: arm64: Handle PSCI call from the guest

Jintack Lim
2017-01-09T06:24:18Z

VMs used to execute hvc #0 for the psci call. However, when we come to
provide virtual EL2 to the VM, the host OS inside the VM also calls
kvm_call_hyp which is also hvc #0. So, it's hard to differentiate
between them from the host hypervisor's point of view.

So, let the VM execute smc for the psci call. On ARMv8.3, even if EL3 is
not implemented, a smc instruction executed at non-secure EL1 is trapped
to EL2 if HCR_EL2.TSC==1, rather than being treated as UNDEFINED. So,
the host hypervisor can handle this psci call without any confusion.

Signed-off-by: Jintack Lim <jintack@cs.columbia.edu>
---
arch/arm64/kvm/handle_exit.c | 23 +++++++++++++++++++++--
1 file changed, 21 insertions(+), 2 deletions(-)

diff --git a/arch/arm64/kvm/handle_exit.c b/arch/arm64/kvm/handle_exit.c
index 208be16..ce6d2ef 100644
--- a/arch/arm64/kvm/handle_exit.c
+++ b/arch/arm64/kvm/handle_exit.c
@@ -64,8 +64,27 @@ static int handle_hvc(struct kvm_vcpu *vcpu, struct kvm_run *run)

static int handle_smc(struct kvm_vcpu *vcpu, struct kvm_run *run)
{
- kvm_inject_undefined(vcpu);
- return 1;
+ int ret;
+
+ /* If imm is non-zero, it's not defined */
+ if (kvm_vcpu_hvc_get_imm(vcpu)) {
+ kvm_inject_undefined(vcpu);
+ return 1;
+ }
+
+ /*
+ * If imm is zero, it's a psci call.
+ * Note that on ARMv8.3, even if EL3 is not implemented, SMC executed
+ * at Non-secure EL1 is trapped to EL2 if HCR_EL2.TSC==1, rather than
+ * being treated as UNDEFINED.
+ */
+ ret = kvm_psci_call(vcpu);
+ if (ret < 0) {
+ kvm_inject_undefined(vcpu);
+ return 1;
+ }
+
+ return ret;
}

/**
--
1.9.1