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

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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>
This commit is contained in:
David Woodhouse 2024-10-19 18:15:43 +01:00 committed by Oliver Upton
parent 2f2d469598
commit 97413cea1c
3 changed files with 54 additions and 0 deletions
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10
Documentation/virt/kvm/api.rst
View File

@ -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 */

6
arch/arm64/include/uapi/asm/kvm.h
View File

@ -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)

38
arch/arm64/kvm/psci.c
View File

@ -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);
}