ARM/ARM64: KVM: Emulate PSCI v0.2 SYSTEM_OFF and SYSTEM_RESET

The PSCI v0.2 SYSTEM_OFF and SYSTEM_RESET functions are system-level
functions hence cannot be fully emulated by in-kernel PSCI emulation code.

To tackle this, we forward PSCI v0.2 SYSTEM_OFF and SYSTEM_RESET function
calls from vcpu to user space (i.e. QEMU or KVMTOOL) via kvm_run structure
using KVM_EXIT_SYSTEM_EVENT exit reasons.

Signed-off-by: Anup Patel <anup.patel@linaro.org>
Signed-off-by: Pranavkumar Sawargaonkar <pranavkumar@linaro.org>
Reviewed-by: Christoffer Dall <christoffer.dall@linaro.org>
Acked-by: Marc Zyngier <marc.zyngier@arm.com>
Signed-off-by: Christoffer Dall <christoffer.dall@linaro.org>

1 files changed, 43 insertions, 3 deletions

diff --git a/arch/arm/kvm/psci.c b/arch/arm/kvm/psci.c
index 14e6fa6c8e35..59362131b79f 100644
--- a/arch/arm/kvm/psci.c
+++ b/arch/arm/kvm/psci.c
@@ -85,6 +85,23 @@ static unsigned long kvm_psci_vcpu_on(struct kvm_vcpu *source_vcpu)
         return PSCI_RET_SUCCESS;
 }
 
+static void kvm_prepare_system_event(struct kvm_vcpu *vcpu, u32 type)
+{
+        memset(&vcpu->run->system_event, 0, sizeof(vcpu->run->system_event));
+        vcpu->run->system_event.type = type;
+        vcpu->run->exit_reason = KVM_EXIT_SYSTEM_EVENT;
+}
+
+static void kvm_psci_system_off(struct kvm_vcpu *vcpu)
+{
+        kvm_prepare_system_event(vcpu, KVM_SYSTEM_EVENT_SHUTDOWN);
+}
+
+static void kvm_psci_system_reset(struct kvm_vcpu *vcpu)
+{
+        kvm_prepare_system_event(vcpu, KVM_SYSTEM_EVENT_RESET);
+}
+
 int kvm_psci_version(struct kvm_vcpu *vcpu)
 {
         if (test_bit(KVM_ARM_VCPU_PSCI_0_2, vcpu->arch.features))
@@ -95,6 +112,7 @@ int kvm_psci_version(struct kvm_vcpu *vcpu)
 
 static int kvm_psci_0_2_call(struct kvm_vcpu *vcpu)
 {
+        int ret = 1;
         unsigned long psci_fn = *vcpu_reg(vcpu, 0) & ~((u32) 0);
         unsigned long val;
 
@@ -114,13 +132,35 @@ static int kvm_psci_0_2_call(struct kvm_vcpu *vcpu)
         case PSCI_0_2_FN64_CPU_ON:
                 val = kvm_psci_vcpu_on(vcpu);
                 break;
+        case PSCI_0_2_FN_SYSTEM_OFF:
+                kvm_psci_system_off(vcpu);
+                /*
+                 * We should'nt be going back to guest VCPU after
+                 * receiving SYSTEM_OFF request.
+                 *
+                 * If user space accidently/deliberately resumes
+                 * guest VCPU after SYSTEM_OFF request then guest
+                 * VCPU should see internal failure from PSCI return
+                 * value. To achieve this, we preload r0 (or x0) with
+                 * PSCI return value INTERNAL_FAILURE.
+                 */
+                val = PSCI_RET_INTERNAL_FAILURE;
+                ret = 0;
+                break;
+        case PSCI_0_2_FN_SYSTEM_RESET:
+                kvm_psci_system_reset(vcpu);
+                /*
+                 * Same reason as SYSTEM_OFF for preloading r0 (or x0)
+                 * with PSCI return value INTERNAL_FAILURE.
+                 */
+                val = PSCI_RET_INTERNAL_FAILURE;
+                ret = 0;
+                break;
         case PSCI_0_2_FN_CPU_SUSPEND:
         case PSCI_0_2_FN_AFFINITY_INFO:
         case PSCI_0_2_FN_MIGRATE:
         case PSCI_0_2_FN_MIGRATE_INFO_TYPE:
         case PSCI_0_2_FN_MIGRATE_INFO_UP_CPU:
-        case PSCI_0_2_FN_SYSTEM_OFF:
-        case PSCI_0_2_FN_SYSTEM_RESET:
         case PSCI_0_2_FN64_CPU_SUSPEND:
         case PSCI_0_2_FN64_AFFINITY_INFO:
         case PSCI_0_2_FN64_MIGRATE:
@@ -132,7 +172,7 @@ static int kvm_psci_0_2_call(struct kvm_vcpu *vcpu)
         }
 
         *vcpu_reg(vcpu, 0) = val;
-        return 1;
+        return ret;
 }
 
 static int kvm_psci_0_1_call(struct kvm_vcpu *vcpu)