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Date:   Thu, 4 Feb 2021 14:36:19 +0000
From:   Will Deacon <will@kernel.org>
To:     Quentin Perret <qperret@google.com>
Cc:     Catalin Marinas <catalin.marinas@arm.com>,
        Marc Zyngier <maz@kernel.org>,
        James Morse <james.morse@arm.com>,
        Julien Thierry <julien.thierry.kdev@gmail.com>,
        Suzuki K Poulose <suzuki.poulose@arm.com>,
        Rob Herring <robh+dt@kernel.org>,
        Frank Rowand <frowand.list@gmail.com>,
        devicetree@vger.kernel.org, android-kvm@google.com,
        linux-kernel@vger.kernel.org, kernel-team@android.com,
        kvmarm@lists.cs.columbia.edu, linux-arm-kernel@lists.infradead.org,
        Fuad Tabba <tabba@google.com>,
        Mark Rutland <mark.rutland@arm.com>,
        David Brazdil <dbrazdil@google.com>
Subject: Re: [RFC PATCH v2 24/26] KVM: arm64: Make memcache anonymous in
 pgtable allocator
Message-ID: <20210204143618.GA20815@willie-the-truck>
References: <20210108121524.656872-1-qperret@google.com>
 <20210108121524.656872-25-qperret@google.com>
 <20210203155944.GH18974@willie-the-truck>
 <YBwDrBH8p0aEpKKC@google.com>
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On Thu, Feb 04, 2021 at 02:24:44PM +0000, Quentin Perret wrote:
> On Wednesday 03 Feb 2021 at 15:59:44 (+0000), Will Deacon wrote:
> > On Fri, Jan 08, 2021 at 12:15:22PM +0000, Quentin Perret wrote:
> > > The current stage2 page-table allocator uses a memcache to get
> > > pre-allocated pages when it needs any. To allow re-using this code at
> > > EL2 which uses a concept of memory pools, make the memcache argument to
> > > kvm_pgtable_stage2_map() anonymous. and let the mm_ops zalloc_page()
> > > callbacks use it the way they need to.
> > > 
> > > Signed-off-by: Quentin Perret <qperret@google.com>
> > > ---
> > >  arch/arm64/include/asm/kvm_pgtable.h | 6 +++---
> > >  arch/arm64/kvm/hyp/pgtable.c         | 4 ++--
> > >  2 files changed, 5 insertions(+), 5 deletions(-)
> > > 
> > > diff --git a/arch/arm64/include/asm/kvm_pgtable.h b/arch/arm64/include/asm/kvm_pgtable.h
> > > index 8e8f1d2c5e0e..d846bc3d3b77 100644
> > > --- a/arch/arm64/include/asm/kvm_pgtable.h
> > > +++ b/arch/arm64/include/asm/kvm_pgtable.h
> > > @@ -176,8 +176,8 @@ void kvm_pgtable_stage2_destroy(struct kvm_pgtable *pgt);
> > >   * @size:	Size of the mapping.
> > >   * @phys:	Physical address of the memory to map.
> > >   * @prot:	Permissions and attributes for the mapping.
> > > - * @mc:		Cache of pre-allocated GFP_PGTABLE_USER memory from which to
> > > - *		allocate page-table pages.
> > > + * @mc:		Cache of pre-allocated memory from which to allocate page-table
> > > + *		pages.
> > 
> > We should probably mention that this memory must be zeroed, since I don't
> > think the page-table code takes care of that.
> 
> OK, though I think this is unrelated to this change -- this is already
> true today I believe. Anyhow, I'll pile a change on top.

It is, but GFP_PGTABLE_USER implies __GFP_ZERO, so the existing comment
captures that.

Will