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Message-ID: <86h6gyz1x6.wl-maz@kernel.org>
Date: Fri, 22 Mar 2024 16:06:29 +0000
From: Marc Zyngier <maz@...nel.org>
To: David Woodhouse <dwmw2@...radead.org>
Cc: linux-arm-kernel@...ts.infradead.org,
kvm@...r.kernel.org,
Paolo Bonzini <pbonzini@...hat.com>,
Jonathan Corbet <corbet@....net>,
Oliver Upton <oliver.upton@...ux.dev>,
James Morse <james.morse@....com>,
Suzuki K Poulose <suzuki.poulose@....com>,
Zenghui Yu <yuzenghui@...wei.com>,
Catalin Marinas <catalin.marinas@....com>,
Will Deacon <will@...nel.org>,
Mark Rutland <mark.rutland@....com>,
Lorenzo Pieralisi <lpieralisi@...nel.org>,
"Rafael J. Wysocki" <rafael@...nel.org>,
Len Brown <len.brown@...el.com>,
Pavel Machek <pavel@....cz>,
David Woodhouse <dwmw@...zon.co.uk>,
Mostafa Saleh <smostafa@...gle.com>,
Jean-Philippe Brucker <jean-philippe@...aro.org>,
linux-doc@...r.kernel.org,
linux-kernel@...r.kernel.org,
kvmarm@...ts.linux.dev,
linux-pm@...r.kernel.org
Subject: Re: [RFC PATCH v3 3/5] KVM: arm64: Add PSCI v1.3 SYSTEM_OFF2 function for hibernation
On Tue, 19 Mar 2024 12:59:04 +0000,
David Woodhouse <dwmw2@...radead.org> wrote:
>
> From: David Woodhouse <dwmw@...zon.co.uk>
>
> The PSCI v1.3 specification (alpha) 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).
>
> The beta version will be changed to say that PSCI_FEATURES returns a bit
> mask of the supported hibernate types, which is implemented here.
>
> Although this new feature is inflicted unconditionally on unexpecting
> userspace, it ought to be mostly OK because it still results in the same
> KVM_SYSTEM_EVENT_SHUTDOWN event, just with a new flag which hopefully
> won't cause userspace to get unhappy.
>
> Signed-off-by: David Woodhouse <dwmw@...zon.co.uk>
> ---
> Documentation/virt/kvm/api.rst | 11 +++++++++
> arch/arm64/include/uapi/asm/kvm.h | 6 +++++
> arch/arm64/kvm/psci.c | 37 +++++++++++++++++++++++++++++++
> 3 files changed, 54 insertions(+)
>
> diff --git a/Documentation/virt/kvm/api.rst b/Documentation/virt/kvm/api.rst
> index 0b5a33ee71ee..ba4ddb13e253 100644
> --- a/Documentation/virt/kvm/api.rst
> +++ b/Documentation/virt/kvm/api.rst
> @@ -6761,6 +6761,10 @@ 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.
>
> @@ -6794,6 +6798,13 @@ 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 f689ef3f2f10..7acf07900c08 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);
> @@ -353,6 +359,11 @@ static int kvm_psci_1_x_call(struct kvm_vcpu *vcpu, u32 minor)
> if (test_bit(KVM_ARCH_FLAG_SYSTEM_SUSPEND_ENABLED, &kvm->arch.flags))
> val = 0;
> break;
> + case PSCI_1_3_FN_SYSTEM_OFF2:
> + case PSCI_1_3_FN64_SYSTEM_OFF2:
> + if (minor >= 3)
> + val = 1UL << PSCI_1_3_HIBERNATE_TYPE_OFF;
> + break;
> case PSCI_1_1_FN_SYSTEM_RESET2:
> case PSCI_1_1_FN64_SYSTEM_RESET2:
nit: please keep the switch ordered by version number.
> if (minor >= 1)
> @@ -374,6 +385,32 @@ static int kvm_psci_1_x_call(struct kvm_vcpu *vcpu, u32 minor)
> return 0;
> }
> 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);
> + if (arg != PSCI_1_3_HIBERNATE_TYPE_OFF) {
> + 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;
> case PSCI_1_1_FN_SYSTEM_RESET2:
> kvm_psci_narrow_to_32bit(vcpu);
> fallthrough;
Same thing here.
Thanks,
M.
--
Without deviation from the norm, progress is not possible.
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