| Message ID | 20210527125134.2116404-8-qperret@google.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | KVM: arm64: Reduce hyp_vmemmap overhead | expand |
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 > >
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(); 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; };
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(-)