KVM: arm64: Add PSCI v1.3 SYSTEM_OFF2 function for hibernation

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@amazon.co.uk>
Reviewed-by: Miguel Luis <miguel.luis@oracle.com>
Link: https://lore.kernel.org/r/20241019172459.2241939-3-dwmw2@infradead.org
[oliver: slight cleanup of comments]
Signed-off-by: Oliver Upton <oliver.upton@linux.dev>

diff --git a/Documentation/virt/kvm/api.rst b/Documentation/virt/kvm/api.rst
index e32471977d0a23933698952ae3d9057fa6aeea3b..206cd0bc4ef4386ae5cfd59cf6c11dc8dea8b6ae 100644 (file)
--- 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 +6892,12 @@ 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.
+
 ::
 
                /* KVM_EXIT_IOAPIC_EOI */

diff --git a/arch/arm64/include/uapi/asm/kvm.h b/arch/arm64/include/uapi/asm/kvm.h
index 964df31da9751c96c984358c66d6f73c8519b2e7..66736ff04011e0fa9fcfb74154d5613bf4ee89f7 100644 (file)
--- 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 1f69b667332b2ba9f9560dd6cfec0d8ce580104e..5d5fb3743b1c9beca65868b814177dec80873f02 100644 (file)
--- 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 +403,33 @@ 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);
+               /*
+                * SYSTEM_OFF2 defaults to HIBERNATE_OFF if arg1 is zero. arg2
+                * 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 the guest after receiving a
+                * SYSTEM_OFF2 request. Preload a return value of
+                * INTERNAL_FAILURE should userspace ignore the exit and resume
+                * the vCPU.
+                */
+               val = PSCI_RET_INTERNAL_FAILURE;
+               ret = 0;
+               break;
        default:
                return kvm_psci_0_2_call(vcpu);
        }