linux-kernel - Re: [PATCH 6.12 3/8] KVM: arm64: Remove host FPSIMD saving for non-protected KVM

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Message-ID: <Z9Q_zW_mM-v2iPHC@arm.com>
Date: Fri, 14 Mar 2025 14:40:13 +0000
From: Catalin Marinas <catalin.marinas@....com>
To: Greg KH <gregkh@...uxfoundation.org>
Cc: Mark Brown <broonie@...nel.org>, Marc Zyngier <maz@...nel.org>,
	Oliver Upton <oliver.upton@...ux.dev>,
	Joey Gouly <joey.gouly@....com>,
	Suzuki K Poulose <suzuki.poulose@....com>,
	Will Deacon <will@...nel.org>, linux-arm-kernel@...ts.infradead.org,
	kvmarm@...ts.linux.dev, linux-kernel@...r.kernel.org,
	stable@...r.kernel.org, Mark Rutland <mark.rutland@....com>,
	Fuad Tabba <tabba@...gle.com>
Subject: Re: [PATCH 6.12 3/8] KVM: arm64: Remove host FPSIMD saving for
 non-protected KVM

On Fri, Mar 14, 2025 at 06:32:45AM +0100, Greg Kroah-Hartman wrote:
> On Fri, Mar 14, 2025 at 12:35:15AM +0000, Mark Brown wrote:
> > From: Mark Rutland <mark.rutland@....com>
> > 
> > Now that the host eagerly saves its own FPSIMD/SVE/SME state,
> > non-protected KVM never needs to save the host FPSIMD/SVE/SME state,
> > and the code to do this is never used. Protected KVM still needs to
> > save/restore the host FPSIMD/SVE state to avoid leaking guest state to
> > the host (and to avoid revealing to the host whether the guest used
> > FPSIMD/SVE/SME), and that code needs to be retained.
> > 
> > Remove the unused code and data structures.
> > 
> > To avoid the need for a stub copy of kvm_hyp_save_fpsimd_host() in the
> > VHE hyp code, the nVHE/hVHE version is moved into the shared switch
> > header, where it is only invoked when KVM is in protected mode.
> > 
> > Signed-off-by: Mark Rutland <mark.rutland@....com>
> > Reviewed-by: Mark Brown <broonie@...nel.org>
> > Tested-by: Mark Brown <broonie@...nel.org>
> > Acked-by: Will Deacon <will@...nel.org>
> > Cc: Catalin Marinas <catalin.marinas@....com>
> > Cc: Fuad Tabba <tabba@...gle.com>
> > Cc: Marc Zyngier <maz@...nel.org>
> > Cc: Oliver Upton <oliver.upton@...ux.dev>
> > Reviewed-by: Oliver Upton <oliver.upton@...ux.dev>
> > Link: https://lore.kernel.org/r/20250210195226.1215254-3-mark.rutland@arm.com
> > Signed-off-by: Marc Zyngier <maz@...nel.org>
> > Signed-off-by: Mark Brown <broonie@...nel.org>
> > ---
> 
> What is the upstream git id for this on?

It seems to be 8eca7f6d5100 ("KVM: arm64: Remove host FPSIMD saving for
non-protected KVM").

-- 
Catalin