linux-kernel - Re: [RFC PATCH 09/27] KVM: arm64: Allow using kvm_nvhe

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Message-ID: <20201123140250.GB490744@google.com>
Date:   Mon, 23 Nov 2020 14:02:50 +0000
From:   Quentin Perret <qperret@...gle.com>
To:     David Brazdil <dbrazdil@...gle.com>
Cc:     Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will@...nel.org>, 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>,
        "moderated list:ARM64 PORT (AARCH64 ARCHITECTURE)" 
        <linux-arm-kernel@...ts.infradead.org>,
        open list <linux-kernel@...r.kernel.org>,
        "open list:KERNEL VIRTUAL MACHINE FOR ARM64 (KVM/arm64)" 
        <kvmarm@...ts.cs.columbia.edu>,
        "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE" 
        <devicetree@...r.kernel.org>, kernel-team@...roid.com,
        android-kvm@...gle.com
Subject: Re: [RFC PATCH 09/27] KVM: arm64: Allow using kvm_nvhe_sym() in hyp
 code

On Monday 23 Nov 2020 at 12:57:23 (+0000), David Brazdil wrote:
> > diff --git a/arch/arm64/kvm/arm.c b/arch/arm64/kvm/arm.c
> > index 882eb383bd75..391cf6753a13 100644
> > --- a/arch/arm64/kvm/arm.c
> > +++ b/arch/arm64/kvm/arm.c
> > @@ -1369,7 +1369,7 @@ static void cpu_prepare_hyp_mode(int cpu)
> >  
> >  	params->vector_hyp_va = kern_hyp_va((unsigned long)kvm_ksym_ref(__kvm_hyp_host_vector));
> >  	params->stack_hyp_va = kern_hyp_va(per_cpu(kvm_arm_hyp_stack_page, cpu) + PAGE_SIZE);
> > -	params->entry_hyp_va = kern_hyp_va((unsigned long)kvm_ksym_ref(__kvm_hyp_psci_cpu_entry));
> > +	params->entry_hyp_va = kern_hyp_va((unsigned long)kvm_ksym_ref_nvhe(__kvm_hyp_psci_cpu_entry));
> 
> Why is this change needed?

You mean this line specifically or the whole __kvm_hyp_psci_cpu_entry
thing?

For the latter, it is to avoid having the compiler complain about
__kvm_hyp_psci_cpu_entry being re-defined as a different symbol. If
there is a better way to solve this problem I'm happy to change it -- I
must admit I got a little confused with the namespacing along the way.

Thanks,
Quentin