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

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Message-ID: <YBw72KeLQ5dzSoJi@google.com>
Date:   Thu, 4 Feb 2021 18:24:24 +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 18:13:18 (+0000), Will Deacon wrote:
> I was going from memory, but the loop in __hyp_alloc_pages() searches up to
> HYP_MAX_ORDER, whereas this is _never_ going to succeed beyond some per-pool
> order determined by the size of the pool. But I doubt it matters -- I
> thought we did more than just check a list.

Ah, I see -- I was looking at the __hyp_attach_page() loop.

I think it's a good point, I should be able to figure out a max order
based on the size and alignment of the pool, and cache that in struct
hyp_pool to optimize cases where this is < HYP_MAX_ORDER.
Should be easy enough, I'll see what I can do in v3.

Thanks!
Quentin