Re: [PATCH v4 12/34] KVM: arm64: Introduce a Hyp buddy page allocator

On Wed, Mar 10, 2021 at 05:57:29PM +0000, Quentin Perret wrote:

When memory protection is enabled, the hyp code will require a basic
form of memory management in order to allocate and free memory pages at
EL2. This is needed for various use-cases, including the creation of hyp
mappings or the allocation of stage 2 page tables.

To address these use-case, introduce a simple memory allocator in the
hyp code. The allocator is designed as a conventional 'buddy allocator',
working with a page granularity. It allows to allocate and free
physically contiguous pages from memory 'pools', with a guaranteed order
alignment in the PA space. Each page in a memory pool is associated
with a struct hyp_page which holds the page's metadata, including its
refcount, as well as its current order, hence mimicking the kernel's
buddy system in the GFP infrastructure. The hyp_page metadata are made
accessible through a hyp_vmemmap, following the concept of
SPARSE_VMEMMAP in the kernel.

Signed-off-by: Quentin Perret <redacted>
---
 arch/arm64/kvm/hyp/include/nvhe/gfp.h    |  68 ++++++++
 arch/arm64/kvm/hyp/include/nvhe/memory.h |  28 ++++
 arch/arm64/kvm/hyp/nvhe/Makefile         |   2 +-
 arch/arm64/kvm/hyp/nvhe/page_alloc.c     | 195 +++++++++++++++++++++++
 4 files changed, 292 insertions(+), 1 deletion(-)
 create mode 100644 arch/arm64/kvm/hyp/include/nvhe/gfp.h
 create mode 100644 arch/arm64/kvm/hyp/nvhe/page_alloc.c

Eventually, we can replace the refcount with refcount_t, but for now this
looks pretty good:

Acked-by: Will Deacon <will@kernel.org>

Will

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