From: Marc Zyngier <maz@kernel.org>
To: Quentin Perret <qperret@google.com>
Cc: will@kernel.org, james.morse@arm.com, alexandru.elisei@arm.com,
catalin.marinas@arm.com, suzuki.poulose@arm.com,
linux-arm-kernel@lists.infradead.org,
kvmarm@lists.cs.columbia.edu, kernel-team@android.com,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH 7/7] KVM: arm64: Use less bits for hyp_page refcount
Date: Tue, 01 Jun 2021 16:21:49 +0100 [thread overview]
Message-ID: <87h7ih1ugi.wl-maz@kernel.org> (raw)
In-Reply-To: <20210527125134.2116404-8-qperret@google.com>
On Thu, 27 May 2021 13:51:34 +0100,
Quentin Perret <qperret@google.com> wrote:
>
> The hyp_page refcount is currently encoded on 4 bytes even though we
> never need to count that many objects in a page. Make it 2 bytes to save
> some space in the vmemmap.
>
> As overflows are more likely to happen as well, make sure to catch those
> with a BUG in the increment function.
>
> Signed-off-by: Quentin Perret <qperret@google.com>
> ---
> arch/arm64/kvm/hyp/include/nvhe/gfp.h | 2 ++
> arch/arm64/kvm/hyp/include/nvhe/memory.h | 2 +-
> 2 files changed, 3 insertions(+), 1 deletion(-)
>
> diff --git a/arch/arm64/kvm/hyp/include/nvhe/gfp.h b/arch/arm64/kvm/hyp/include/nvhe/gfp.h
> index d420e5c0845f..a82f73faf41e 100644
> --- a/arch/arm64/kvm/hyp/include/nvhe/gfp.h
> +++ b/arch/arm64/kvm/hyp/include/nvhe/gfp.h
> @@ -24,6 +24,8 @@ struct hyp_pool {
>
> static inline void hyp_page_ref_inc(struct hyp_page *p)
> {
> + if (p->refcount == USHRT_MAX)
> + BUG();
nit: BUG_ON(p->refcount == USHRT_MAX);
> p->refcount++;
> }
>
> diff --git a/arch/arm64/kvm/hyp/include/nvhe/memory.h b/arch/arm64/kvm/hyp/include/nvhe/memory.h
> index 3fe34fa30ea4..592b7edb3edb 100644
> --- a/arch/arm64/kvm/hyp/include/nvhe/memory.h
> +++ b/arch/arm64/kvm/hyp/include/nvhe/memory.h
> @@ -8,7 +8,7 @@
> #include <linux/types.h>
>
> struct hyp_page {
> - unsigned int refcount;
> + unsigned short refcount;
> unsigned short order;
> };
>
> --
> 2.31.1.818.g46aad6cb9e-goog
>
>
--
Without deviation from the norm, progress is not possible.
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prev parent reply other threads:[~2021-06-01 15:23 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-05-27 12:51 [PATCH 0/7] KVM: arm64: Reduce hyp_vmemmap overhead Quentin Perret
2021-05-27 12:51 ` [PATCH 1/7] KVM: arm64: Move hyp_pool locking out of refcount helpers Quentin Perret
2021-06-01 12:02 ` Marc Zyngier
2021-06-01 13:31 ` Quentin Perret
2021-05-27 12:51 ` [PATCH 2/7] KVM: arm64: Use refcount at hyp to check page availability Quentin Perret
2021-05-27 12:51 ` [PATCH 3/7] KVM: arm64: Remove list_head from hyp_page Quentin Perret
2021-06-01 14:38 ` Marc Zyngier
2021-06-01 15:48 ` Quentin Perret
2021-06-01 17:41 ` Marc Zyngier
2021-06-02 9:23 ` Quentin Perret
2021-05-27 12:51 ` [PATCH 4/7] KVM: arm64: Unify MMIO and mem host stage-2 pools Quentin Perret
2021-05-27 12:51 ` [PATCH 5/7] KVM: arm64: Remove hyp_pool pointer from struct hyp_page Quentin Perret
2021-06-01 15:00 ` Marc Zyngier
2021-05-27 12:51 ` [PATCH 6/7] KVM: arm64: Use less bits for hyp_page order Quentin Perret
2021-05-27 12:51 ` [PATCH 7/7] KVM: arm64: Use less bits for hyp_page refcount Quentin Perret
2021-06-01 15:21 ` Marc Zyngier [this message]
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