Re: [PATCH v6 1/6] firmware/psci: Add definitions for PSCI v1.3 specification

Re: [PATCH v6 1/6] firmware/psci: Add definitions for PSCI v1.3 specification

[Miguel Luis]

> On 19 Oct 2024, at 17:15, David Woodhouse <dwmw2@infradead.org> wrote:
> 
> From: David Woodhouse <dwmw@amazon.co.uk>
> 
> The v1.3 PSCI spec (https://developer.arm.com/documentation/den0022) adds
> the SYSTEM_OFF2 function. Add definitions for it and its hibernation type
> parameter.
> 
> Signed-off-by: David Woodhouse <dwmw@amazon.co.uk>
> ---
> include/uapi/linux/psci.h | 5 +++++
> 1 file changed, 5 insertions(+)
> 
> diff --git a/include/uapi/linux/psci.h b/include/uapi/linux/psci.h
> index 42a40ad3fb62..81759ff385e6 100644
> --- a/include/uapi/linux/psci.h
> +++ b/include/uapi/linux/psci.h
> @@ -59,6 +59,7 @@
> #define PSCI_1_1_FN_SYSTEM_RESET2 PSCI_0_2_FN(18)
> #define PSCI_1_1_FN_MEM_PROTECT PSCI_0_2_FN(19)
> #define PSCI_1_1_FN_MEM_PROTECT_CHECK_RANGE PSCI_0_2_FN(20)
> +#define PSCI_1_3_FN_SYSTEM_OFF2 PSCI_0_2_FN(21)
> 
> #define PSCI_1_0_FN64_CPU_DEFAULT_SUSPEND PSCI_0_2_FN64(12)
> #define PSCI_1_0_FN64_NODE_HW_STATE PSCI_0_2_FN64(13)
> @@ -68,6 +69,7 @@
> 
> #define PSCI_1_1_FN64_SYSTEM_RESET2 PSCI_0_2_FN64(18)
> #define PSCI_1_1_FN64_MEM_PROTECT_CHECK_RANGE PSCI_0_2_FN64(20)
> +#define PSCI_1_3_FN64_SYSTEM_OFF2 PSCI_0_2_FN64(21)
> 
> /* PSCI v0.2 power state encoding for CPU_SUSPEND function */
> #define PSCI_0_2_POWER_STATE_ID_MASK 0xffff
> @@ -100,6 +102,9 @@
> #define PSCI_1_1_RESET_TYPE_SYSTEM_WARM_RESET 0
> #define PSCI_1_1_RESET_TYPE_VENDOR_START 0x80000000U
> 
> +/* PSCI v1.3 hibernate type for SYSTEM_OFF2 */
> +#define PSCI_1_3_OFF_TYPE_HIBERNATE_OFF BIT(0)
> +

Reviewed-by: Miguel Luis <miguel.luis@oracle.com>

> /* PSCI version decoding (independent of PSCI version) */
> #define PSCI_VERSION_MAJOR_SHIFT 16
> #define PSCI_VERSION_MINOR_MASK \
> -- 
> 2.44.0
> 

Re: [PATCH v6 2/6] KVM: arm64: Add PSCI v1.3 SYSTEM_OFF2 function for hibernation

[Miguel Luis]

Hi David,

> On 19 Oct 2024, at 17:15, David Woodhouse <dwmw2@infradead.org> wrote:
> 
> From: David Woodhouse <dwmw@amazon.co.uk>
> 
> 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>
> ---
> 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).

I don’t think that ‘0x0’ adds something to what’s already explained
before, IMO.

> +
> ::
> 
> /* 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;

Other than that it looks good to me:

Reviewed-by: Miguel Luis <miguel.luis@oracle.com>

Thanks,
Miguel

> default:
> return kvm_psci_0_2_call(vcpu);
> }
> -- 
> 2.44.0
> 

Re: [PATCH v6 3/6] KVM: arm64: Add support for PSCI v1.2 and v1.3

[Miguel Luis]

> On 19 Oct 2024, at 17:15, David Woodhouse <dwmw2@infradead.org> wrote:
> 
> From: David Woodhouse <dwmw@amazon.co.uk>
> 
> As with PSCI v1.1 in commit 512865d83fd9 ("KVM: arm64: Bump guest PSCI
> version to 1.1"), expose v1.3 to the guest by default. The SYSTEM_OFF2
> call which is exposed by doing so is compatible for userspace because
> it's just a new flag in the event that KVM raises, in precisely the same
> way that SYSTEM_RESET2 was compatible when v1.1 was enabled by default.
> 
> Signed-off-by: David Woodhouse <dwmw@amazon.co.uk>
> ---
> arch/arm64/kvm/hypercalls.c | 2 ++
> arch/arm64/kvm/psci.c       | 6 +++++-
> include/kvm/arm_psci.h      | 4 +++-
> 3 files changed, 10 insertions(+), 2 deletions(-)
> 
> diff --git a/arch/arm64/kvm/hypercalls.c b/arch/arm64/kvm/hypercalls.c
> index 5763d979d8ca..9c6267ca2b82 100644
> --- a/arch/arm64/kvm/hypercalls.c
> +++ b/arch/arm64/kvm/hypercalls.c
> @@ -575,6 +575,8 @@ int kvm_arm_set_fw_reg(struct kvm_vcpu *vcpu, const struct kvm_one_reg *reg)
> case KVM_ARM_PSCI_0_2:
> case KVM_ARM_PSCI_1_0:
> case KVM_ARM_PSCI_1_1:
> + case KVM_ARM_PSCI_1_2:
> + case KVM_ARM_PSCI_1_3:
> if (!wants_02)
> return -EINVAL;
> vcpu->kvm->arch.psci_version = val;
> diff --git a/arch/arm64/kvm/psci.c b/arch/arm64/kvm/psci.c
> index df834f2e928e..6c24a9252fa3 100644
> --- a/arch/arm64/kvm/psci.c
> +++ b/arch/arm64/kvm/psci.c
> @@ -328,7 +328,7 @@ static int kvm_psci_1_x_call(struct kvm_vcpu *vcpu, u32 minor)
> 
> switch(psci_fn) {
> case PSCI_0_2_FN_PSCI_VERSION:
> - val = minor == 0 ? KVM_ARM_PSCI_1_0 : KVM_ARM_PSCI_1_1;
> + val = PSCI_VERSION(1, minor);
> break;
> case PSCI_1_0_FN_PSCI_FEATURES:
> arg = smccc_get_arg1(vcpu);
> @@ -493,6 +493,10 @@ int kvm_psci_call(struct kvm_vcpu *vcpu)
> }
> 
> switch (version) {
> + case KVM_ARM_PSCI_1_3:
> + return kvm_psci_1_x_call(vcpu, 3);
> + case KVM_ARM_PSCI_1_2:
> + return kvm_psci_1_x_call(vcpu, 2);
> case KVM_ARM_PSCI_1_1:
> return kvm_psci_1_x_call(vcpu, 1);
> case KVM_ARM_PSCI_1_0:
> diff --git a/include/kvm/arm_psci.h b/include/kvm/arm_psci.h
> index e8fb624013d1..cbaec804eb83 100644
> --- a/include/kvm/arm_psci.h
> +++ b/include/kvm/arm_psci.h
> @@ -14,8 +14,10 @@
> #define KVM_ARM_PSCI_0_2 PSCI_VERSION(0, 2)
> #define KVM_ARM_PSCI_1_0 PSCI_VERSION(1, 0)
> #define KVM_ARM_PSCI_1_1 PSCI_VERSION(1, 1)
> +#define KVM_ARM_PSCI_1_2 PSCI_VERSION(1, 2)
> +#define KVM_ARM_PSCI_1_3 PSCI_VERSION(1, 3)
> 
> -#define KVM_ARM_PSCI_LATEST KVM_ARM_PSCI_1_1
> +#define KVM_ARM_PSCI_LATEST KVM_ARM_PSCI_1_3
> 

Reviewed-by: Miguel Luis <miguel.luis@oracle.com>

> static inline int kvm_psci_version(struct kvm_vcpu *vcpu)
> {
> -- 
> 2.44.0
> 

Re: [PATCH v6 5/6] KVM: arm64: nvhe: Pass through PSCI v1.3 SYSTEM_OFF2 call

[Miguel Luis]

> On 19 Oct 2024, at 17:15, David Woodhouse <dwmw2@infradead.org> wrote:
> 
> From: David Woodhouse <dwmw@amazon.co.uk>
> 
> Pass through the SYSTEM_OFF2 function for hibernation, just like SYSTEM_OFF.
> 
> Signed-off-by: David Woodhouse <dwmw@amazon.co.uk>
> ---
> arch/arm64/kvm/hyp/nvhe/psci-relay.c | 2 ++
> 1 file changed, 2 insertions(+)
> 
> diff --git a/arch/arm64/kvm/hyp/nvhe/psci-relay.c b/arch/arm64/kvm/hyp/nvhe/psci-relay.c
> index dfe8fe0f7eaf..9c2ce1e0e99a 100644
> --- a/arch/arm64/kvm/hyp/nvhe/psci-relay.c
> +++ b/arch/arm64/kvm/hyp/nvhe/psci-relay.c
> @@ -265,6 +265,8 @@ static unsigned long psci_1_0_handler(u64 func_id, struct kvm_cpu_context *host_
> case PSCI_1_0_FN_PSCI_FEATURES:
> case PSCI_1_0_FN_SET_SUSPEND_MODE:
> case PSCI_1_1_FN64_SYSTEM_RESET2:
> + case PSCI_1_3_FN_SYSTEM_OFF2:
> + case PSCI_1_3_FN64_SYSTEM_OFF2:

Reviewed-by: Miguel Luis <miguel.luis@oracle.com>

> return psci_forward(host_ctxt);
> case PSCI_1_0_FN64_SYSTEM_SUSPEND:
> return psci_system_suspend(func_id, host_ctxt);
> -- 
> 2.44.0
> 
> 

Re: (subset) [PATCH v6 0/6] Add PSCI v1.3 SYSTEM_OFF2 support for hibernation

[Oliver Upton]

On Sat, 19 Oct 2024 18:15:41 +0100, David Woodhouse wrote:
> The PSCI v1.3 spec (https://developer.arm.com/documentation/den0022)
> adds support for a SYSTEM_OFF2 function enabling a HIBERNATE_OFF state
> which is analogous to ACPI S4. 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).
> 
> [...]

I grabbed the KVM portions of this series, as they look ready to go. Happy
to take the last one through kvmarm tree w/ acks, and can toss it on top.

Applied to kvmarm/next, thanks!

[1/6] firmware/psci: Add definitions for PSCI v1.3 specification
      https://git.kernel.org/kvmarm/kvmarm/c/2f2d46959808
[2/6] KVM: arm64: Add PSCI v1.3 SYSTEM_OFF2 function for hibernation
      https://git.kernel.org/kvmarm/kvmarm/c/97413cea1c48
[3/6] KVM: arm64: Add support for PSCI v1.2 and v1.3
      https://git.kernel.org/kvmarm/kvmarm/c/8be82d536a9f
[4/6] KVM: selftests: Add test for PSCI SYSTEM_OFF2
      https://git.kernel.org/kvmarm/kvmarm/c/72be5aa6be4a
[5/6] KVM: arm64: nvhe: Pass through PSCI v1.3 SYSTEM_OFF2 call
      https://git.kernel.org/kvmarm/kvmarm/c/94f985c39a1e

--
Best,
Oliver

Re: (subset) [PATCH v6 0/6] Add PSCI v1.3 SYSTEM_OFF2 support for hibernation

[Catalin Marinas]

On Fri, Oct 25, 2024 at 10:12:41PM +0000, Oliver Upton wrote:
> On Sat, 19 Oct 2024 18:15:41 +0100, David Woodhouse wrote:
> > The PSCI v1.3 spec (https://developer.arm.com/documentation/den0022)
> > adds support for a SYSTEM_OFF2 function enabling a HIBERNATE_OFF state
> > which is analogous to ACPI S4. 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).
> > 
> > [...]
> 
> I grabbed the KVM portions of this series, as they look ready to go. Happy
> to take the last one through kvmarm tree w/ acks, and can toss it on top.

Happy for you to take the last patch as well through the KVM tree. Feel
free to adjust the code comment as you see fit.

-- 
Catalin

Re: (subset) [PATCH v6 0/6] Add PSCI v1.3 SYSTEM_OFF2 support for hibernation

[David Woodhouse]

[-- Attachment #1: Type: text/plain, Size: 1108 bytes --]

On Thu, 2024-10-31 at 12:15 +0000, Catalin Marinas wrote:
> On Fri, Oct 25, 2024 at 10:12:41PM +0000, Oliver Upton wrote:
> > On Sat, 19 Oct 2024 18:15:41 +0100, David Woodhouse wrote:
> > > The PSCI v1.3 spec (https://developer.arm.com/documentation/den0022)
> > > adds support for a SYSTEM_OFF2 function enabling a HIBERNATE_OFF state
> > > which is analogous to ACPI S4. 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).
> > > 
> > > [...]
> > 
> > I grabbed the KVM portions of this series, as they look ready to go. Happy
> > to take the last one through kvmarm tree w/ acks, and can toss it on top.
> 
> Happy for you to take the last patch as well through the KVM tree. Feel
> free to adjust the code comment as you see fit.

Thanks. that's probably the best option, as it depends on the
definitions in psci.h.



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Re: [PATCH v6 6/6] arm64: Use SYSTEM_OFF2 PSCI call to power off for hibernate

[Miguel Luis]

Hi David,

> On 19 Oct 2024, at 17:15, David Woodhouse <dwmw2@infradead.org> wrote:
> 
> From: David Woodhouse <dwmw@amazon.co.uk>
> 
> 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 handle that state appropriately on subsequent launches.
> 
> Since commit 60c0d45a7f7a ("efi/arm64: use UEFI for system reset and
> poweroff") the EFI shutdown method is deliberately preferred over PSCI
> or other methods. So register a SYS_OFF_MODE_POWER_OFF handler which
> *only* handles the hibernation, leaving the original PSCI SYSTEM_OFF as
> a last resort via the legacy pm_power_off function pointer.
> 
> The hibernation code already exports a system_entering_hibernation()
> function which is be used by the higher-priority handler to check for
> hibernation. That existing function just returns the value of a static
> boolean variable from hibernate.c, which was previously only set in the
> hibernation_platform_enter() code path. Set the same flag in the simpler
> code path around the call to kernel_power_off() too.
> 
> An alternative way to hook SYSTEM_OFF2 into the hibernation code would
> be to register a platform_hibernation_ops structure with an ->enter()
> method which makes the new SYSTEM_OFF2 call. But that would have the
> unwanted side-effect of making hibernation take a completely different
> code path in hibernation_platform_enter(), invoking a lot of special dpm
> callbacks.
> 
> Another option might be to add a new SYS_OFF_MODE_HIBERNATE mode, with
> fallback to SYS_OFF_MODE_POWER_OFF. Or to use the sys_off_data to
> indicate whether the power off is for hibernation.
> 
> But this version works and is relatively simple.
> 
> Signed-off-by: David Woodhouse <dwmw@amazon.co.uk>
> Acked-by: Rafael J. Wysocki <rafael@kernel.org>
> ---
> drivers/firmware/psci/psci.c | 42 ++++++++++++++++++++++++++++++++++++
> kernel/power/hibernate.c     |  5 ++++-
> 2 files changed, 46 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/firmware/psci/psci.c b/drivers/firmware/psci/psci.c
> index 2328ca58bba6..8809455a61a6 100644
> --- a/drivers/firmware/psci/psci.c
> +++ b/drivers/firmware/psci/psci.c
> @@ -78,6 +78,7 @@ struct psci_0_1_function_ids get_psci_0_1_function_ids(void)
> 
> static u32 psci_cpu_suspend_feature;
> static bool psci_system_reset2_supported;
> +static bool psci_system_off2_hibernate_supported;
> 
> static inline bool psci_has_ext_power_state(void)
> {
> @@ -333,6 +334,33 @@ static void psci_sys_poweroff(void)
> invoke_psci_fn(PSCI_0_2_FN_SYSTEM_OFF, 0, 0, 0);
> }
> 
> +#ifdef CONFIG_HIBERNATION
> +static int psci_sys_hibernate(struct sys_off_data *data)
> +{
> + /*
> + * Zero is an acceptable alternative to PSCI_1_3_OFF_TYPE_HIBERNATE_OFF
> + * and is supported by hypervisors implementing an earlier version
> + * of the pSCI v1.3 spec.

s/pSCI/PSCI

> + */
> + if (system_entering_hibernation())
> + invoke_psci_fn(PSCI_FN_NATIVE(1_3, SYSTEM_OFF2),
> +       0 /*PSCI_1_3_OFF_TYPE_HIBERNATE_OFF*/, 0, 0);

Perhaps spec. F.b. could be accommodated by first invoking SYSTEM_OFF2 with
PSCI_1_3_OFF_TYPE_HIBERNATE_OFF and checking its return value in case of a
fallback to an invocation with 0x0 ?

Thanks.
Miguel

> + return NOTIFY_DONE;
> +}
> +
> +static int __init psci_hibernate_init(void)
> +{
> + if (psci_system_off2_hibernate_supported) {
> + /* Higher priority than EFI shutdown, but only for hibernate */
> + register_sys_off_handler(SYS_OFF_MODE_POWER_OFF,
> + SYS_OFF_PRIO_FIRMWARE + 2,
> + psci_sys_hibernate, NULL);
> + }
> + return 0;
> +}
> +subsys_initcall(psci_hibernate_init);
> +#endif
> +
> static int psci_features(u32 psci_func_id)
> {
> return invoke_psci_fn(PSCI_1_0_FN_PSCI_FEATURES,
> @@ -364,6 +392,7 @@ static const struct {
> PSCI_ID_NATIVE(1_1, SYSTEM_RESET2),
> PSCI_ID(1_1, MEM_PROTECT),
> PSCI_ID_NATIVE(1_1, MEM_PROTECT_CHECK_RANGE),
> + PSCI_ID_NATIVE(1_3, SYSTEM_OFF2),
> };
> 
> static int psci_debugfs_read(struct seq_file *s, void *data)
> @@ -525,6 +554,18 @@ static void __init psci_init_system_reset2(void)
> psci_system_reset2_supported = true;
> }
> 
> +static void __init psci_init_system_off2(void)
> +{
> + int ret;
> +
> + ret = psci_features(PSCI_FN_NATIVE(1_3, SYSTEM_OFF2));
> + if (ret < 0)
> + return;
> +
> + if (ret & PSCI_1_3_OFF_TYPE_HIBERNATE_OFF)
> + psci_system_off2_hibernate_supported = true;
> +}
> +
> static void __init psci_init_system_suspend(void)
> {
> int ret;
> @@ -655,6 +696,7 @@ static int __init psci_probe(void)
> psci_init_cpu_suspend();
> psci_init_system_suspend();
> psci_init_system_reset2();
> + psci_init_system_off2();
> kvm_init_hyp_services();
> }
> 
> diff --git a/kernel/power/hibernate.c b/kernel/power/hibernate.c
> index e35829d36039..1f87aa01ba44 100644
> --- a/kernel/power/hibernate.c
> +++ b/kernel/power/hibernate.c
> @@ -685,8 +685,11 @@ static void power_down(void)
> }
> fallthrough;
> case HIBERNATION_SHUTDOWN:
> - if (kernel_can_power_off())
> + if (kernel_can_power_off()) {
> + entering_platform_hibernation = true;
> kernel_power_off();
> + entering_platform_hibernation = false;
> + }
> break;
> }
> kernel_halt();
> -- 
> 2.44.0
> 

Re: [PATCH v6 6/6] arm64: Use SYSTEM_OFF2 PSCI call to power off for hibernate

[David Woodhouse]

On 24 October 2024 14:54:41 CEST, Miguel Luis <miguel.luis@oracle.com> wrote:
>Perhaps spec. F.b. could be accommodated by first invoking SYSTEM_OFF2 with
>PSCI_1_3_OFF_TYPE_HIBERNATE_OFF and checking its return value in case of a
>fallback to an invocation with 0x0 ?

I wasn't aware there was any point. Are there any hypervisors which actually implemented it that way? Amazon Linux and Ubuntu guests already just use zero.

We could add it later if such a hypervisor (now in violation of F.b) turns up, I suppose?

Re: [PATCH v6 6/6] arm64: Use SYSTEM_OFF2 PSCI call to power off for hibernate

[Oliver Upton]

Hi,

On Thu, Oct 24, 2024 at 03:48:26PM +0200, David Woodhouse wrote:
> On 24 October 2024 14:54:41 CEST, Miguel Luis <miguel.luis@oracle.com> wrote:
> >Perhaps spec. F.b. could be accommodated by first invoking SYSTEM_OFF2 with
> >PSCI_1_3_OFF_TYPE_HIBERNATE_OFF and checking its return value in case of a
> >fallback to an invocation with 0x0 ?

This already complies with F.b.

The PSCI implementation is required to accept either 0 or 1 for
HIBERNATE_OFF. Using 0 seems like a good choice for compatibility since ...

> I wasn't aware there was any point. Are there any hypervisors which actually implemented it that way? Amazon Linux and Ubuntu guests already just use zero.
> 
> We could add it later if such a hypervisor (now in violation of F.b) turns up, I suppose?

IIUC, you're really wanting to 0x0 because there are hypervisors out
there that violate the final spec and *only* accept this value.

That's perfectly fine, but it'd help avoid confusion if the supporting
comment was a bit more direct:

	/*
	 * If no hibernate type is specified SYSTEM_OFF2 defaults to
	 * selecting HIBERNATE_OFF.
	 *
	 * There are hypervisors in the wild that violate the spec and
	 * reject calls that explicitly provide a hibernate type. For
	 * compatibility with these nonstandard implementations, pass 0
	 * as the type.
	 */
	 if (system_entering_hibernation())
		invoke_psci_fn(PSCI_FN_NATIVE(1_3, SYSTEM_OFF2), 0 , 0, 0);

Thoughts?

-- 
Thanks,
Oliver

Re: [PATCH v6 6/6] arm64: Use SYSTEM_OFF2 PSCI call to power off for hibernate

[David Woodhouse]

On 24 October 2024 17:44:49 CEST, Oliver Upton <oliver.upton@linux.dev> wrote:
>Hi,
>
>On Thu, Oct 24, 2024 at 03:48:26PM +0200, David Woodhouse wrote:
>> On 24 October 2024 14:54:41 CEST, Miguel Luis <miguel.luis@oracle.com> wrote:
>> >Perhaps spec. F.b. could be accommodated by first invoking SYSTEM_OFF2 with
>> >PSCI_1_3_OFF_TYPE_HIBERNATE_OFF and checking its return value in case of a
>> >fallback to an invocation with 0x0 ?
>
>This already complies with F.b.
>
>The PSCI implementation is required to accept either 0 or 1 for
>HIBERNATE_OFF. Using 0 seems like a good choice for compatibility since ...
>
>> I wasn't aware there was any point. Are there any hypervisors which actually implemented it that way? Amazon Linux and Ubuntu guests already just use zero.
>> 
>> We could add it later if such a hypervisor (now in violation of F.b) turns up, I suppose?
>
>IIUC, you're really wanting to 0x0 because there are hypervisors out
>there that violate the final spec and *only* accept this value.
>
>That's perfectly fine, but it'd help avoid confusion if the supporting
>comment was a bit more direct:
>
>	/*
>	 * If no hibernate type is specified SYSTEM_OFF2 defaults to
>	 * selecting HIBERNATE_OFF.
>	 *
>	 * There are hypervisors in the wild that violate the spec and
>	 * reject calls that explicitly provide a hibernate type. For
>	 * compatibility with these nonstandard implementations, pass 0
>	 * as the type.
>	 */
>	 if (system_entering_hibernation())
>		invoke_psci_fn(PSCI_FN_NATIVE(1_3, SYSTEM_OFF2), 0 , 0, 0);

By the time this makes it into released versions of the guest Linux kernel, that comment won't be true any more.

Re: [PATCH v6 6/6] arm64: Use SYSTEM_OFF2 PSCI call to power off for hibernate

[Oliver Upton]

On Thu, Oct 24, 2024 at 05:56:09PM +0200, David Woodhouse wrote:
> On 24 October 2024 17:44:49 CEST, Oliver Upton <oliver.upton@linux.dev> wrote:
> >IIUC, you're really wanting to 0x0 because there are hypervisors out
> >there that violate the final spec and *only* accept this value.
> >
> >That's perfectly fine, but it'd help avoid confusion if the supporting
> >comment was a bit more direct:
> >
> >	/*
> >	 * If no hibernate type is specified SYSTEM_OFF2 defaults to
> >	 * selecting HIBERNATE_OFF.
> >	 *
> >	 * There are hypervisors in the wild that violate the spec and
> >	 * reject calls that explicitly provide a hibernate type. For
> >	 * compatibility with these nonstandard implementations, pass 0
> >	 * as the type.
> >	 */
> >	 if (system_entering_hibernation())
> >		invoke_psci_fn(PSCI_FN_NATIVE(1_3, SYSTEM_OFF2), 0 , 0, 0);
> 
> By the time this makes it into released versions of the guest Linux kernel, that comment won't be true any more.

Then does it even matter? What is the problem you're trying to solve
with using a particular value for the hibernate type?

Either the goal of this is to make the PSCI client code compatible with
your hypervisor today (and any other implementation based on 'F ALP1') or
we don't care and go with whatever value we want.

Even if the comment eventually becomes stale, there is a ton of value in
documenting the exact implementation decision being made.

-- 
Thanks,
Oliver

Re: [PATCH v6 6/6] arm64: Use SYSTEM_OFF2 PSCI call to power off for hibernate

[David Woodhouse]

On 24 October 2024 21:57:38 CEST, Oliver Upton <oliver.upton@linux.dev> wrote:
>On Thu, Oct 24, 2024 at 05:56:09PM +0200, David Woodhouse wrote:
>> On 24 October 2024 17:44:49 CEST, Oliver Upton <oliver.upton@linux.dev> wrote:
>> >IIUC, you're really wanting to 0x0 because there are hypervisors out
>> >there that violate the final spec and *only* accept this value.
>> >
>> >That's perfectly fine, but it'd help avoid confusion if the supporting
>> >comment was a bit more direct:
>> >
>> >	/*
>> >	 * If no hibernate type is specified SYSTEM_OFF2 defaults to
>> >	 * selecting HIBERNATE_OFF.
>> >	 *
>> >	 * There are hypervisors in the wild that violate the spec and
>> >	 * reject calls that explicitly provide a hibernate type. For
>> >	 * compatibility with these nonstandard implementations, pass 0
>> >	 * as the type.
>> >	 */
>> >	 if (system_entering_hibernation())
>> >		invoke_psci_fn(PSCI_FN_NATIVE(1_3, SYSTEM_OFF2), 0 , 0, 0);
>> 
>> By the time this makes it into released versions of the guest Linux kernel, that comment won't be true any more.
>
>Then does it even matter? What is the problem you're trying to solve
>with using a particular value for the hibernate type?
>
>Either the goal of this is to make the PSCI client code compatible with
>your hypervisor today (and any other implementation based on 'F ALP1') or
>we don't care and go with whatever value we want.
>
>Even if the comment eventually becomes stale, there is a ton of value in
>documenting the exact implementation decision being made.
>

Eventually it won't matter and we can go with whatever value we want. But yes, the goal is to be compatible with the hypervisor *today* until it catches up the changes to the final versions of the spec. I didn't spend much time overthinking the comment. What was it....

	/*
	 * Zero is an acceptable alternative to PSCI_1_3_OFF_TYPE_HIBERNATE_OFF
	 * and is supported by hypervisors implementing an earlier version
	 * of the pSCI v1.3 spec.
	 */

That seems to cover it just fine, I think.

Re: [PATCH v6 6/6] arm64: Use SYSTEM_OFF2 PSCI call to power off for hibernate

[Oliver Upton]

On Fri, Oct 25, 2024 at 08:13:03AM +0200, David Woodhouse wrote:
> On 24 October 2024 21:57:38 CEST, Oliver Upton <oliver.upton@linux.dev> wrote:
> >On Thu, Oct 24, 2024 at 05:56:09PM +0200, David Woodhouse wrote:
> >> On 24 October 2024 17:44:49 CEST, Oliver Upton <oliver.upton@linux.dev> wrote:
> >> >IIUC, you're really wanting to 0x0 because there are hypervisors out
> >> >there that violate the final spec and *only* accept this value.
> >> >
> >> >That's perfectly fine, but it'd help avoid confusion if the supporting
> >> >comment was a bit more direct:
> >> >
> >> >	/*
> >> >	 * If no hibernate type is specified SYSTEM_OFF2 defaults to
> >> >	 * selecting HIBERNATE_OFF.
> >> >	 *
> >> >	 * There are hypervisors in the wild that violate the spec and
> >> >	 * reject calls that explicitly provide a hibernate type. For
> >> >	 * compatibility with these nonstandard implementations, pass 0
> >> >	 * as the type.
> >> >	 */
> >> >	 if (system_entering_hibernation())
> >> >		invoke_psci_fn(PSCI_FN_NATIVE(1_3, SYSTEM_OFF2), 0 , 0, 0);
> >> 
> >> By the time this makes it into released versions of the guest Linux kernel, that comment won't be true any more.
> >
> >Then does it even matter? What is the problem you're trying to solve
> >with using a particular value for the hibernate type?
> >
> >Either the goal of this is to make the PSCI client code compatible with
> >your hypervisor today (and any other implementation based on 'F ALP1') or
> >we don't care and go with whatever value we want.
> >
> >Even if the comment eventually becomes stale, there is a ton of value in
> >documenting the exact implementation decision being made.
> >
> 
> Eventually it won't matter and we can go with whatever value we want. But yes, the goal is to be compatible with the hypervisor *today* until it catches up the changes to the final versions of the spec. I didn't spend much time overthinking the comment. What was it....
> 
> 	/*
> 	 * Zero is an acceptable alternative to PSCI_1_3_OFF_TYPE_HIBERNATE_OFF
> 	 * and is supported by hypervisors implementing an earlier version
> 	 * of the pSCI v1.3 spec.
> 	 */
> 
> That seems to cover it just fine, I think.

No. You're leaving the work for the reader to:

 (1) Figure out what you're talking about
 (2) Go dig up an "earlier version" of the spec
 (3) Realise that it means certain hypervisors only take 0x0 as an
     argument

If you speak *directly* about the problem you're trying to address then
reviewers are less likely to get hung up on what you're trying to do.

I'm genuinely at a loss for why you would want to present this as an
"acceptable alterantive" rather than a functional requirement for this
driver to run on your hypervisor.

-- 
Thanks,
Oliver

Re: [PATCH v6 6/6] arm64: Use SYSTEM_OFF2 PSCI call to power off for hibernate

[David Woodhouse]

[-- Attachment #1: Type: text/plain, Size: 2271 bytes --]

On Fri, 2024-10-25 at 13:40 -0700, Oliver Upton wrote:
> 
> No. You're leaving the work for the reader to:
> 
>  (1) Figure out what you're talking about
>  (2) Go dig up an "earlier version" of the spec
>  (3) Realise that it means certain hypervisors only take 0x0 as an
>      argument

No. There's no need to dig up an 'earlier version' of the spec. The
current F.b release says, "if the value of this parameter is 0x0, the
implementation defaults to selecting HIBERNATE_OFF". That's what makes
it an acceptable alternative.

> If you speak *directly* about the problem you're trying to address then
> reviewers are less likely to get hung up on what you're trying to do.

The "problem" this comment addresses is a reader who looks at this code
and wonders why it uses zero instead of HIBERNATE_OFF.

Firstly, that reader needs to spot the text, in the *current* version
of the spec as cited above, which makes it clear that it's a perfectly
acceptable alternative.

Secondly, that reader needs to know why we chose zero over
HIBERNATE_OFF, which is also explained fairly succinctly: because it's
compatible with hypervisors implementing an earlier version of the
spec.

> I'm genuinely at a loss for why you would want to present this as an
> "acceptable alterantive" rather than a functional requirement for this
> driver to run on your hypervisor.

Because "my" hypervisor is a live product which actually gets security
fixes and updates. If it wasn't for the silly season of "thou shalt not
ship *anything* except security fixes and stuff that's going to be
announced at a big conference at the end of the month", the change to
make it accept the new value of HIBERNATE_OFF would already have been
deployed.

And *even* with the silly season delaying non-critical hypervisor
changes, your suggested wording will *still* probably not be true by
the time the comment is included in an actual release of the Linux
kernel.

But honestly, it isn't a hill I'm prepared to die on. If you insist on
changing the comment to your 'There are hypervisors in the wile that
violate the spec...' version, by all means go ahead and do so. I'll
follow up with a patch to correct it in a few weeks when it becomes
obsolete.

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Re: [PATCH v6 6/6] arm64: Use SYSTEM_OFF2 PSCI call to power off for hibernate

[Catalin Marinas]

On Sat, Oct 19, 2024 at 06:15:47PM +0100, David Woodhouse wrote:
> From: David Woodhouse <dwmw@amazon.co.uk>
> 
> 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 handle that state appropriately on subsequent launches.
> 
> Since commit 60c0d45a7f7a ("efi/arm64: use UEFI for system reset and
> poweroff") the EFI shutdown method is deliberately preferred over PSCI
> or other methods. So register a SYS_OFF_MODE_POWER_OFF handler which
> *only* handles the hibernation, leaving the original PSCI SYSTEM_OFF as
> a last resort via the legacy pm_power_off function pointer.
> 
> The hibernation code already exports a system_entering_hibernation()
> function which is be used by the higher-priority handler to check for
> hibernation. That existing function just returns the value of a static
> boolean variable from hibernate.c, which was previously only set in the
> hibernation_platform_enter() code path. Set the same flag in the simpler
> code path around the call to kernel_power_off() too.
> 
> An alternative way to hook SYSTEM_OFF2 into the hibernation code would
> be to register a platform_hibernation_ops structure with an ->enter()
> method which makes the new SYSTEM_OFF2 call. But that would have the
> unwanted side-effect of making hibernation take a completely different
> code path in hibernation_platform_enter(), invoking a lot of special dpm
> callbacks.
> 
> Another option might be to add a new SYS_OFF_MODE_HIBERNATE mode, with
> fallback to SYS_OFF_MODE_POWER_OFF. Or to use the sys_off_data to
> indicate whether the power off is for hibernation.
> 
> But this version works and is relatively simple.
> 
> Signed-off-by: David Woodhouse <dwmw@amazon.co.uk>
> Acked-by: Rafael J. Wysocki <rafael@kernel.org>

Acked-by: Catalin Marinas <catalin.marinas@arm.com>

Re: [PATCH v6 6/6] arm64: Use SYSTEM_OFF2 PSCI call to power off for hibernate

[Lorenzo Pieralisi]

On Sat, Oct 19, 2024 at 06:15:47PM +0100, David Woodhouse wrote:

[...]

> +#ifdef CONFIG_HIBERNATION
> +static int psci_sys_hibernate(struct sys_off_data *data)
> +{
> +	/*
> +	 * Zero is an acceptable alternative to PSCI_1_3_OFF_TYPE_HIBERNATE_OFF
> +	 * and is supported by hypervisors implementing an earlier version
> +	 * of the pSCI v1.3 spec.
> +	 */

It is obvious but with this patch applied a host kernel would start executing
SYSTEM_OFF2 too if supported in firmware to hibernate, it is not a hypervisor
only code path.

Related to that: is it now always safe to override

commit 60c0d45a7f7a ("efi/arm64: use UEFI for system reset and poweroff")

for hibernation ? It is not very clear to me why overriding PSCI for
poweroff was the right thing to do - tried to follow that patch history but
the question remains (it is related to UpdateCapsule() but I don't know
how that applies to the hibernation use case).

As far as type == 0 is concerned:

I don't think the issue here is really PSCI 1.3 ALP1 vs PSCI 1.3 Issue
F.b, by reading the PSCI 1.3 Issue F.b specs (note (e) page 96) it looks
like there was a (superseded) PSCI 1.3 Issue F (september 2024 -
superseded in October 2024 - just reading the specs timeline) that allowed an
implementation to return INVALID_PARAMETERS if type == 0 - there should
be no firwmare out there that followed it - it was short lived.

Lorenzo

> +	if (system_entering_hibernation())
> +		invoke_psci_fn(PSCI_FN_NATIVE(1_3, SYSTEM_OFF2),
> +			       0 /*PSCI_1_3_OFF_TYPE_HIBERNATE_OFF*/, 0, 0);
> +	return NOTIFY_DONE;
> +}
> +
> +static int __init psci_hibernate_init(void)
> +{
> +	if (psci_system_off2_hibernate_supported) {
> +		/* Higher priority than EFI shutdown, but only for hibernate */
> +		register_sys_off_handler(SYS_OFF_MODE_POWER_OFF,
> +					 SYS_OFF_PRIO_FIRMWARE + 2,
> +					 psci_sys_hibernate, NULL);
> +	}
> +	return 0;
> +}
> +subsys_initcall(psci_hibernate_init);
> +#endif
> +
>  static int psci_features(u32 psci_func_id)
>  {
>  	return invoke_psci_fn(PSCI_1_0_FN_PSCI_FEATURES,
> @@ -364,6 +392,7 @@ static const struct {
>  	PSCI_ID_NATIVE(1_1, SYSTEM_RESET2),
>  	PSCI_ID(1_1, MEM_PROTECT),
>  	PSCI_ID_NATIVE(1_1, MEM_PROTECT_CHECK_RANGE),
> +	PSCI_ID_NATIVE(1_3, SYSTEM_OFF2),
>  };
>  
>  static int psci_debugfs_read(struct seq_file *s, void *data)
> @@ -525,6 +554,18 @@ static void __init psci_init_system_reset2(void)
>  		psci_system_reset2_supported = true;
>  }
>  
> +static void __init psci_init_system_off2(void)
> +{
> +	int ret;
> +
> +	ret = psci_features(PSCI_FN_NATIVE(1_3, SYSTEM_OFF2));
> +	if (ret < 0)
> +		return;
> +
> +	if (ret & PSCI_1_3_OFF_TYPE_HIBERNATE_OFF)
> +		psci_system_off2_hibernate_supported = true;
> +}
> +
>  static void __init psci_init_system_suspend(void)
>  {
>  	int ret;
> @@ -655,6 +696,7 @@ static int __init psci_probe(void)
>  		psci_init_cpu_suspend();
>  		psci_init_system_suspend();
>  		psci_init_system_reset2();
> +		psci_init_system_off2();
>  		kvm_init_hyp_services();
>  	}
>  
> diff --git a/kernel/power/hibernate.c b/kernel/power/hibernate.c
> index e35829d36039..1f87aa01ba44 100644
> --- a/kernel/power/hibernate.c
> +++ b/kernel/power/hibernate.c
> @@ -685,8 +685,11 @@ static void power_down(void)
>  		}
>  		fallthrough;
>  	case HIBERNATION_SHUTDOWN:
> -		if (kernel_can_power_off())
> +		if (kernel_can_power_off()) {
> +			entering_platform_hibernation = true;
>  			kernel_power_off();
> +			entering_platform_hibernation = false;
> +		}
>  		break;
>  	}
>  	kernel_halt();
> -- 
> 2.44.0
> 

Re: [PATCH v6 6/6] arm64: Use SYSTEM_OFF2 PSCI call to power off for hibernate

[Lorenzo Pieralisi]

[+Ard, Sami, for EFI]

On Thu, Oct 31, 2024 at 06:55:43PM +0100, Lorenzo Pieralisi wrote:
> On Sat, Oct 19, 2024 at 06:15:47PM +0100, David Woodhouse wrote:
> 
> [...]
> 
> > +#ifdef CONFIG_HIBERNATION
> > +static int psci_sys_hibernate(struct sys_off_data *data)
> > +{
> > +	/*
> > +	 * Zero is an acceptable alternative to PSCI_1_3_OFF_TYPE_HIBERNATE_OFF
> > +	 * and is supported by hypervisors implementing an earlier version
> > +	 * of the pSCI v1.3 spec.
> > +	 */
> 
> It is obvious but with this patch applied a host kernel would start executing
> SYSTEM_OFF2 too if supported in firmware to hibernate, it is not a hypervisor
> only code path.
> 
> Related to that: is it now always safe to override
> 
> commit 60c0d45a7f7a ("efi/arm64: use UEFI for system reset and poweroff")
> 
> for hibernation ? It is not very clear to me why overriding PSCI for
> poweroff was the right thing to do - tried to follow that patch history but
> the question remains (it is related to UpdateCapsule() but I don't know
> how that applies to the hibernation use case).

RFC: It is unclear to me what happens in current mainline if we try to
hibernate with EFI runtime services enabled and a capsule update pending (we
issue EFI ResetSystem(EFI_RESET_SHUTDOWN,..) which might not be compatible
with the reset required by the pending capsule update request) what happens
in this case I don't know but at least the choice is all contained in
EFI firmware.

Then if in the same scenario now we are switching to PSCI SYSTEM_OFF2 for the
hibernate reset I suspect that what happens to the in-flight capsule
update requests strictly depends on what "reset" PSCI SYSTEM_OFF2 will
end up doing ?

I think this is just a corner case and it is unlikely it has been ever
tested (is it even possible ? Looking at EFI folks) - it would be good
to clarify it at least to make sure we understand this code path.

Thanks,
Lorenzo

Re: [PATCH v6 6/6] arm64: Use SYSTEM_OFF2 PSCI call to power off for hibernate

[Ard Biesheuvel]

On Fri, 1 Nov 2024 at 18:49, Lorenzo Pieralisi <lpieralisi@kernel.org> wrote:
>
> [+Ard, Sami, for EFI]
>
> On Thu, Oct 31, 2024 at 06:55:43PM +0100, Lorenzo Pieralisi wrote:
> > On Sat, Oct 19, 2024 at 06:15:47PM +0100, David Woodhouse wrote:
> >
> > [...]
> >
> > > +#ifdef CONFIG_HIBERNATION
> > > +static int psci_sys_hibernate(struct sys_off_data *data)
> > > +{
> > > +   /*
> > > +    * Zero is an acceptable alternative to PSCI_1_3_OFF_TYPE_HIBERNATE_OFF
> > > +    * and is supported by hypervisors implementing an earlier version
> > > +    * of the pSCI v1.3 spec.
> > > +    */
> >
> > It is obvious but with this patch applied a host kernel would start executing
> > SYSTEM_OFF2 too if supported in firmware to hibernate, it is not a hypervisor
> > only code path.
> >
> > Related to that: is it now always safe to override
> >
> > commit 60c0d45a7f7a ("efi/arm64: use UEFI for system reset and poweroff")
> >
> > for hibernation ? It is not very clear to me why overriding PSCI for
> > poweroff was the right thing to do - tried to follow that patch history but
> > the question remains (it is related to UpdateCapsule() but I don't know
> > how that applies to the hibernation use case).
>
> RFC: It is unclear to me what happens in current mainline if we try to
> hibernate with EFI runtime services enabled and a capsule update pending (we
> issue EFI ResetSystem(EFI_RESET_SHUTDOWN,..) which might not be compatible
> with the reset required by the pending capsule update request) what happens
> in this case I don't know but at least the choice is all contained in
> EFI firmware.
>
> Then if in the same scenario now we are switching to PSCI SYSTEM_OFF2 for the
> hibernate reset I suspect that what happens to the in-flight capsule
> update requests strictly depends on what "reset" PSCI SYSTEM_OFF2 will
> end up doing ?
>
> I think this is just a corner case and it is unlikely it has been ever
> tested (is it even possible ? Looking at EFI folks) - it would be good
> to clarify it at least to make sure we understand this code path.
>

I'm not aware of any OS that actually uses capsule update at runtime
(both Windows and Linux queue up the capsule and call the
UpdateCapsule() runtime service at boot time after a reboot).

So it is unlikely that this would break anything, and I'd actually be
inclined to disable capsule update at runtime altogether.

I will also note that hibernation with EFI is flaky in general, given
that EFI memory regions may move around

Re: [PATCH v6 6/6] arm64: Use SYSTEM_OFF2 PSCI call to power off for hibernate

[Lorenzo Pieralisi]

On Mon, Nov 04, 2024 at 02:54:12PM +0100, Ard Biesheuvel wrote:
> On Fri, 1 Nov 2024 at 18:49, Lorenzo Pieralisi <lpieralisi@kernel.org> wrote:
> >
> > [+Ard, Sami, for EFI]
> >
> > On Thu, Oct 31, 2024 at 06:55:43PM +0100, Lorenzo Pieralisi wrote:
> > > On Sat, Oct 19, 2024 at 06:15:47PM +0100, David Woodhouse wrote:
> > >
> > > [...]
> > >
> > > > +#ifdef CONFIG_HIBERNATION
> > > > +static int psci_sys_hibernate(struct sys_off_data *data)
> > > > +{
> > > > +   /*
> > > > +    * Zero is an acceptable alternative to PSCI_1_3_OFF_TYPE_HIBERNATE_OFF
> > > > +    * and is supported by hypervisors implementing an earlier version
> > > > +    * of the pSCI v1.3 spec.
> > > > +    */
> > >
> > > It is obvious but with this patch applied a host kernel would start executing
> > > SYSTEM_OFF2 too if supported in firmware to hibernate, it is not a hypervisor
> > > only code path.
> > >
> > > Related to that: is it now always safe to override
> > >
> > > commit 60c0d45a7f7a ("efi/arm64: use UEFI for system reset and poweroff")
> > >
> > > for hibernation ? It is not very clear to me why overriding PSCI for
> > > poweroff was the right thing to do - tried to follow that patch history but
> > > the question remains (it is related to UpdateCapsule() but I don't know
> > > how that applies to the hibernation use case).
> >
> > RFC: It is unclear to me what happens in current mainline if we try to
> > hibernate with EFI runtime services enabled and a capsule update pending (we
> > issue EFI ResetSystem(EFI_RESET_SHUTDOWN,..) which might not be compatible
> > with the reset required by the pending capsule update request) what happens
> > in this case I don't know but at least the choice is all contained in
> > EFI firmware.
> >
> > Then if in the same scenario now we are switching to PSCI SYSTEM_OFF2 for the
> > hibernate reset I suspect that what happens to the in-flight capsule
> > update requests strictly depends on what "reset" PSCI SYSTEM_OFF2 will
> > end up doing ?
> >
> > I think this is just a corner case and it is unlikely it has been ever
> > tested (is it even possible ? Looking at EFI folks) - it would be good
> > to clarify it at least to make sure we understand this code path.
> >
> 
> I'm not aware of any OS that actually uses capsule update at runtime
> (both Windows and Linux queue up the capsule and call the
> UpdateCapsule() runtime service at boot time after a reboot).
> 
> So it is unlikely that this would break anything, and I'd actually be
> inclined to disable capsule update at runtime altogether.
> 
> I will also note that hibernation with EFI is flaky in general, given
> that EFI memory regions may move around

Thank you for chiming in, I think we are OK (I don't think this patch
will create more issues than the ones that are already there for hibernate
anyway) - the reasoning behind the change is in the commit logs.

Lorenzo

Re: (subset) [PATCH v6 0/6] Add PSCI v1.3 SYSTEM_OFF2 support for hibernation

[Oliver Upton]

On Sat, 19 Oct 2024 18:15:41 +0100, David Woodhouse wrote:
> The PSCI v1.3 spec (https://developer.arm.com/documentation/den0022)
> adds support for a SYSTEM_OFF2 function enabling a HIBERNATE_OFF state
> which is analogous to ACPI S4. 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).
> 
> [...]

Thanks Catalin for the ack, as promised:

Applied to kvmarm/next, thanks!

[6/6] arm64: Use SYSTEM_OFF2 PSCI call to power off for hibernate
      https://git.kernel.org/kvmarm/kvmarm/c/3e251afaec9a

--
Best,
Oliver

Re: (subset) [PATCH v6 0/6] Add PSCI v1.3 SYSTEM_OFF2 support for hibernation

[David Woodhouse]

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On Thu, 2024-10-31 at 17:56 +0000, Oliver Upton wrote:
> On Sat, 19 Oct 2024 18:15:41 +0100, David Woodhouse wrote:
> > The PSCI v1.3 spec (https://developer.arm.com/documentation/den0022)
> > adds support for a SYSTEM_OFF2 function enabling a HIBERNATE_OFF state
> > which is analogous to ACPI S4. 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).
> > 
> > [...]
> 
> Thanks Catalin for the ack, as promised:
> 
> Applied to kvmarm/next, thanks!
> 
> [6/6] arm64: Use SYSTEM_OFF2 PSCI call to power off for hibernate
>       https://git.kernel.org/kvmarm/kvmarm/c/3e251afaec9a

Thank you.

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