[PATCH 7/7] KVM: arm64: Use less bits for hyp_page refcount
From: Quentin Perret <hidden>
Date: 2021-05-27 12:52:09
Also in:
kvmarm, lkml
Subsystem:
arm64 port (aarch64 architecture), kernel virtual machine for arm64 (kvm/arm64), the rest · Maintainers:
Catalin Marinas, Will Deacon, Marc Zyngier, Oliver Upton, Linus Torvalds
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 <redacted> --- 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(); 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
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