On Thu, 27 May 2021 13:51:34 +0100,
Quentin Perret <qperret@xxxxxxxxxx> 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@xxxxxxxxxx>
> ---
> 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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