linux-kernel - Re: [PATCH 0/3] KVM: arm64: Simplify pKVM memory transitions

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Message-Id: <173667852147.882737.8982373220700597868.b4-ty@kernel.org>
Date: Sun, 12 Jan 2025 10:42:07 +0000
From: Marc Zyngier <maz@...nel.org>
To: Oliver Upton <oliver.upton@...ux.dev>,
	Joey Gouly <joey.gouly@....com>,
	Suzuki K Poulose <suzuki.poulose@....com>,
	Zenghui Yu <yuzenghui@...wei.com>,
	Catalin Marinas <catalin.marinas@....com>,
	Will Deacon <will@...nel.org>,
	Quentin Perret <qperret@...gle.com>
Cc: Fuad Tabba <tabba@...gle.com>,
	Vincent Donnefort <vdonnefort@...gle.com>,
	linux-arm-kernel@...ts.infradead.org,
	kvmarm@...ts.linux.dev,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 0/3] KVM: arm64: Simplify pKVM memory transitions

On Fri, 10 Jan 2025 12:19:33 +0000, Quentin Perret wrote:
> Since its early days, pKVM has formalized memory 'transitions' (shares
> and donations) using 'struct pkvm_mem_transition' and bunch of helpers
> to manipulate it. The intention was for all transitions to use this
> machinery to ensure we're checking things consistently. However, as
> development progressed, it became clear that the rigidity of this model
> made it really difficult to use in some use-cases which ended-up
> side-stepping it entirely. That is the case for the
> hyp_{un}pin_shared_mem() and host_{un}share_guest() paths upstream which
> use lower level helpers directly, as well as for several other pKVM
> features that should land upstream in the future (ex: when a guest
> relinquishes a page during ballooning, when annotating a page that is
> being DMA'd to, ...). On top of this, the pkvm_mem_transition machinery
> requires a lot of boilerplate which makes the code hard to read, but
> also adds layers of indirection that no compilers seems to see through,
> hence leading to suboptimal generated code.
> 
> [...]

Applied to next, thanks!

[1/3] KVM: arm64: Drop pkvm_mem_transition for FF-A
      commit: ed2f80fd76bd2c6e00d2e90f78d21a3055ee3562
[2/3] KVM: arm64: Drop pkvm_mem_transition for host/hyp sharing
      commit: d3b3473c15e4391673d8dca9c36dd5e9c3a8a4ac
[3/3] KVM: arm64: Drop pkvm_mem_transition for host/hyp donations
      commit: 2d2aa2eb275fa6f80d68ed442c3328273bbbecba

Cheers,

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