Re: [RFC PATCH 0/2] Add PSCI v1.3 SYSTEM_OFF2 support for hibernation

Marc Zyngier
2024-03-12T15:24:33Z

On Tue, 12 Mar 2024 13:51:27 +0000,
David Woodhouse <dwmw2@infradead.org> wrote:
>
> The upcoming PSCI v1.3 specification adds support for a SYSTEM_OFF2

Pointer to the spec? Crucially, this is in the Alpha state, meaning
that it is still subject to change [1].

> 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 adds support for it to KVM, and to the guest hibernate code.
>
> Strictly, we should perhaps also allow the guest to detect PSCI v1.3,
> but when v1.1 was added in commit 512865d83fd9 it was done
> unconditionally, which seems wrong. Shouldn't we have a way for
> userspace to control what gets exposed, rather than silently changing
> the guest behaviour with newer host kernels? Should I add a
> KVM_CAP_ARM_PSCI_VERSION?

Do you mean something like 85bd0ba1ff98?

M.

[1] https://documentation-service.arm.com/static/65e59325837c4d065f6556a6

--
Without deviation from the norm, progress is not possible.