linux-kernel - Re: [RFC PATCH v2 2/4] KVM: arm64: Add PSCI SYSTEM

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Message-ID: <6a2107864d45bd6ac403c218d68bf97025eca971.camel@infradead.org>
Date: Mon, 18 Mar 2024 17:54:06 +0000
From: David Woodhouse <dwmw2@...radead.org>
To: Marc Zyngier <maz@...nel.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>, 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 v2 2/4] KVM: arm64: Add PSCI SYSTEM_OFF2 function
 for hibernation

On Mon, 2024-03-18 at 17:29 +0000, Marc Zyngier wrote:
> 
> Again, I really oppose this way of doing things. We already have an
> infrastructure for selecting PSCI levels. You may not like it, but it
> exists, and I'm not going entertain supporting yet another bike-shed
> model. Adding an orthogonal cap for a feature that is specific to a
> new PSCI version is just awful.

Huh? This isn't a "new bike-shed model". This is a straight copy of
what we *already* have for SYSTEM_RESET2.

If I were bike-shedding, I wouldn't do separate caps for them; I'd have
done it as a *bitmask* of the optional PSCI calls that should be
enabled.

The *mandatory* ones should obviously come from the PSCI version alone,
but I can't see how that makes sense for the optional ones...

> Please make PSCI 1.3 the only version of PSCI supporting suspend in a
> non-optional way, and be done with it.

SYSTEM_OFF2 is an *optional* feature in PSCI v1.3. As are
CLEAR_INV_MEMREGION and CLEAR_INV_MEMREGION_ATTRIBUTES.

Are you suggesting that enabling v1.3 should automatically enable *all*
of the optional features that were defined in that version (and
previous versions) of the spec?

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