From: David Woodhouse <dwmw@xxxxxxxxxxxx>
The PSCI v1.3 specification adds support for a SYSTEM_OFF2 function
which is analogous to ACPI S4 state. This will allow hosting
environments to determine that a guest is hibernated rather than just
powered off, and ensure that they preserve the virtual environment
appropriately to allow the guest to resume safely (or bump the
hardware_signature in the FACS to trigger a clean reboot instead).
This feature is safe to enable unconditionally (in a subsequent commit)
because it is exposed to userspace through the existing
KVM_SYSTEM_EVENT_SHUTDOWN event, just with an additional flag which
userspace can use to know that the instance intended hibernation instead
of a plain power-off.
As with SYSTEM_RESET2, there is only one type available (in this case
HIBERNATE_OFF), and it is not explicitly reported to userspace through
the event; userspace can get it from the registers if it cares).
Signed-off-by: David Woodhouse <dwmw@xxxxxxxxxxxx>
---
Documentation/virt/kvm/api.rst | 11 ++++++++
arch/arm64/include/uapi/asm/kvm.h | 6 +++++
arch/arm64/kvm/psci.c | 44 +++++++++++++++++++++++++++++++
3 files changed, 61 insertions(+)
diff --git a/Documentation/virt/kvm/api.rst b/Documentation/virt/kvm/api.rst
index e32471977d0a..1ec076d806e6 100644
--- a/Documentation/virt/kvm/api.rst
+++ b/Documentation/virt/kvm/api.rst
@@ -6855,6 +6855,10 @@ the first `ndata` items (possibly zero) of the data array are valid.
the guest issued a SYSTEM_RESET2 call according to v1.1 of the PSCI
specification.
+ - for arm64, data[0] is set to KVM_SYSTEM_EVENT_SHUTDOWN_FLAG_PSCI_OFF2
+ if the guest issued a SYSTEM_OFF2 call according to v1.3 of the PSCI
+ specification.
+
- for RISC-V, data[0] is set to the value of the second argument of the
``sbi_system_reset`` call.
@@ -6888,6 +6892,13 @@ either:
- Deny the guest request to suspend the VM. See ARM DEN0022D.b 5.19.2
"Caller responsibilities" for possible return values.
+Hibernation using the PSCI SYSTEM_OFF2 call is enabled when PSCI v1.3
+is enabled. If a guest invokes the PSCI SYSTEM_OFF2 function, KVM will
+exit to userspace with the KVM_SYSTEM_EVENT_SHUTDOWN event type and with
+data[0] set to KVM_SYSTEM_EVENT_SHUTDOWN_FLAG_PSCI_OFF2. The only
+supported hibernate type for the SYSTEM_OFF2 function is HIBERNATE_OFF
+0x0).
+
::
/* KVM_EXIT_IOAPIC_EOI */
diff --git a/arch/arm64/include/uapi/asm/kvm.h b/arch/arm64/include/uapi/asm/kvm.h
index 964df31da975..66736ff04011 100644
--- a/arch/arm64/include/uapi/asm/kvm.h
+++ b/arch/arm64/include/uapi/asm/kvm.h
@@ -484,6 +484,12 @@ enum {
*/
#define KVM_SYSTEM_EVENT_RESET_FLAG_PSCI_RESET2 (1ULL << 0)
+/*
+ * Shutdown caused by a PSCI v1.3 SYSTEM_OFF2 call.
+ * Valid only when the system event has a type of KVM_SYSTEM_EVENT_SHUTDOWN.
+ */
+#define KVM_SYSTEM_EVENT_SHUTDOWN_FLAG_PSCI_OFF2 (1ULL << 0)
+
/* run->fail_entry.hardware_entry_failure_reason codes. */
#define KVM_EXIT_FAIL_ENTRY_CPU_UNSUPPORTED (1ULL << 0)
diff --git a/arch/arm64/kvm/psci.c b/arch/arm64/kvm/psci.c
index 1f69b667332b..df834f2e928e 100644
--- a/arch/arm64/kvm/psci.c
+++ b/arch/arm64/kvm/psci.c
@@ -194,6 +194,12 @@ static void kvm_psci_system_off(struct kvm_vcpu *vcpu)
kvm_prepare_system_event(vcpu, KVM_SYSTEM_EVENT_SHUTDOWN, 0);
}
+static void kvm_psci_system_off2(struct kvm_vcpu *vcpu)
+{
+ kvm_prepare_system_event(vcpu, KVM_SYSTEM_EVENT_SHUTDOWN,
+ KVM_SYSTEM_EVENT_SHUTDOWN_FLAG_PSCI_OFF2);
+}
+
static void kvm_psci_system_reset(struct kvm_vcpu *vcpu)
{
kvm_prepare_system_event(vcpu, KVM_SYSTEM_EVENT_RESET, 0);
@@ -358,6 +364,11 @@ static int kvm_psci_1_x_call(struct kvm_vcpu *vcpu, u32 minor)
if (minor >= 1)
val = 0;
break;
+ case PSCI_1_3_FN_SYSTEM_OFF2:
+ case PSCI_1_3_FN64_SYSTEM_OFF2:
+ if (minor >= 3)
+ val = PSCI_1_3_OFF_TYPE_HIBERNATE_OFF;
+ break;
}
break;
case PSCI_1_0_FN_SYSTEM_SUSPEND:
@@ -392,6 +403,39 @@ static int kvm_psci_1_x_call(struct kvm_vcpu *vcpu, u32 minor)
break;
}
break;
+ case PSCI_1_3_FN_SYSTEM_OFF2:
+ kvm_psci_narrow_to_32bit(vcpu);
+ fallthrough;
+ case PSCI_1_3_FN64_SYSTEM_OFF2:
+ if (minor < 3)
+ break;
+
+ arg = smccc_get_arg1(vcpu);
+ /*
+ * PSCI v1.3 issue F.b requires that zero be accepted to mean
+ * HIBERNATE_OFF (in line with pre-publication versions of the
+ * spec, and thus some actual implementations in the wild).
+ * The second argument must be zero.
+ */
+ if ((arg && arg != PSCI_1_3_OFF_TYPE_HIBERNATE_OFF) ||
+ smccc_get_arg2(vcpu) != 0) {
+ val = PSCI_RET_INVALID_PARAMS;
+ break;
+ }
+ kvm_psci_system_off2(vcpu);
+ /*
+ * We shouldn't be going back to guest VCPU after
+ * receiving SYSTEM_OFF2 request.
+ *
+ * If user space accidentally/deliberately resumes
+ * guest VCPU after SYSTEM_OFF2 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;
default:
return kvm_psci_0_2_call(vcpu);
}
--
2.44.0
