linux-kernel - Re: [RFC PATCH v2 16/26] KVM: arm64: Prepare Hyp memory protection

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Date:   Tue, 9 Feb 2021 10:00:29 +0000
From:   Quentin Perret <qperret@...gle.com>
To:     Will Deacon <will@...nel.org>
Cc:     Catalin Marinas <catalin.marinas@....com>,
        Marc Zyngier <maz@...nel.org>,
        James Morse <james.morse@....com>,
        Julien Thierry <julien.thierry.kdev@...il.com>,
        Suzuki K Poulose <suzuki.poulose@....com>,
        Rob Herring <robh+dt@...nel.org>,
        Frank Rowand <frowand.list@...il.com>,
        devicetree@...r.kernel.org, android-kvm@...gle.com,
        linux-kernel@...r.kernel.org, kernel-team@...roid.com,
        kvmarm@...ts.cs.columbia.edu, linux-arm-kernel@...ts.infradead.org,
        Fuad Tabba <tabba@...gle.com>,
        Mark Rutland <mark.rutland@....com>,
        David Brazdil <dbrazdil@...gle.com>
Subject: Re: [RFC PATCH v2 16/26] KVM: arm64: Prepare Hyp memory protection

On Thursday 04 Feb 2021 at 10:47:08 (+0000), Quentin Perret wrote:
> On Wednesday 03 Feb 2021 at 14:37:10 (+0000), Will Deacon wrote:
> > > +static void handle___pkvm_init(struct kvm_cpu_context *host_ctxt)
> > > +{
> > > +	DECLARE_REG(phys_addr_t, phys, host_ctxt, 1);
> > > +	DECLARE_REG(unsigned long, size, host_ctxt, 2);
> > > +	DECLARE_REG(unsigned long, nr_cpus, host_ctxt, 3);
> > > +	DECLARE_REG(unsigned long *, per_cpu_base, host_ctxt, 4);
> > > +
> > > +	cpu_reg(host_ctxt, 1) = __pkvm_init(phys, size, nr_cpus, per_cpu_base);
> > 
> > __pkvm_init() doesn't return, so I think this assignment back into host_ctxt
> > is confusing.
> 
> Very good point, I'll get rid of this.

Actually not, I think I'll leave it like that. __pkvm_init can return an
error, which is why I did this in the first place And it is useful for
debugging to have it propagated back to the host.

Thanks,
Quentin