linux-kernel - Re: [RFC PATCH v2 12/26] KVM: arm64: Introduce a Hyp buddy page allocator

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Message-ID: <YBw6uInyY+AlE7D3@google.com>
Date:   Thu, 4 Feb 2021 18:19:36 +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 12/26] KVM: arm64: Introduce a Hyp buddy page
 allocator

On Thursday 04 Feb 2021 at 14:31:08 (+0000), Will Deacon wrote:
> Just feels a bit backwards having __find_buddy() take an order parameter,
> yet then return a page of the wrong order! __hyp_extract_page() always
> passes the p->order as the order,

Gotcha, so maybe this is just a naming problem. __find_buddy() is simply
a helper to lookup/index the vmemmap, but it's perfectly possible that
the 'destination' page that is being indexed has already been allocated,
and split up multiple time (and so at a different order), etc ... And
that is the caller's job to decide.

How about __lookup_potential_buddy() ? Any suggestion?