linux-kernel - Re: [PATCH v3 01/15] KVM: arm64: Check if running in VHE from kvm_host_owns_hyp

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Message-ID: <YbNYCJOOARfUPKq1@google.com>
Date:   Fri, 10 Dec 2021 13:37:12 +0000
From:   Quentin Perret <qperret@...gle.com>
To:     Will Deacon <will@...nel.org>
Cc:     Marc Zyngier <maz@...nel.org>, James Morse <james.morse@....com>,
        Alexandru Elisei <alexandru.elisei@....com>,
        Suzuki K Poulose <suzuki.poulose@....com>,
        Catalin Marinas <catalin.marinas@....com>,
        linux-arm-kernel@...ts.infradead.org, kvmarm@...ts.cs.columbia.edu,
        linux-kernel@...r.kernel.org, kernel-team@...roid.com
Subject: Re: [PATCH v3 01/15] KVM: arm64: Check if running in VHE from
 kvm_host_owns_hyp_mappings()

On Thursday 09 Dec 2021 at 10:10:54 (+0000), Will Deacon wrote:
> On Wed, Dec 01, 2021 at 05:03:55PM +0000, Quentin Perret wrote:
> > The kvm_host_owns_hyp_mappings() function should return true if and only
> > if the host kernel is responsible for creating the hypervisor stage-1
> > mappings. That is only possible in standard non-VHE mode, or during boot
> > in protected nVHE mode. But either way, non of this makes sense in VHE,
> > so make sure to catch this case as well, hence making the function
> > return sensible values in any context (VHE or not).
> > 
> > Suggested-by: Marc Zyngier <maz@...nel.org>
> > Signed-off-by: Quentin Perret <qperret@...gle.com>
> > ---
> >  arch/arm64/kvm/mmu.c | 3 +++
> >  1 file changed, 3 insertions(+)
> > 
> > diff --git a/arch/arm64/kvm/mmu.c b/arch/arm64/kvm/mmu.c
> > index 326cdfec74a1..f8f1096a297f 100644
> > --- a/arch/arm64/kvm/mmu.c
> > +++ b/arch/arm64/kvm/mmu.c
> > @@ -239,6 +239,9 @@ void free_hyp_pgds(void)
> >  
> >  static bool kvm_host_owns_hyp_mappings(void)
> >  {
> > +	if (is_kernel_in_hyp_mode())
> > +		return false;
> 
> This looks identical to:
> 
> https://lore.kernel.org/r/20211208152300.2478542-7-qperret@google.com

Yep, I figured it made more sense in the other series as it's not
strictly related to this one, so ... :)

Cheers,
Quentin