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SubjectRe: [PATCH v4 16/34] KVM: arm64: Prepare the creation of s1 mappings at EL2
On Wed, Mar 10, 2021 at 05:57:33PM +0000, Quentin Perret wrote:
> When memory protection is enabled, the EL2 code needs the ability to
> create and manage its own page-table. To do so, introduce a new set of
> hypercalls to bootstrap a memory management system at EL2.
>
> This leads to the following boot flow in nVHE Protected mode:
>
> 1. the host allocates memory for the hypervisor very early on, using
> the memblock API;
>
> 2. the host creates a set of stage 1 page-table for EL2, installs the
> EL2 vectors, and issues the __pkvm_init hypercall;
>
> 3. during __pkvm_init, the hypervisor re-creates its stage 1 page-table
> and stores it in the memory pool provided by the host;
>
> 4. the hypervisor then extends its stage 1 mappings to include a
> vmemmap in the EL2 VA space, hence allowing to use the buddy
> allocator introduced in a previous patch;
>
> 5. the hypervisor jumps back in the idmap page, switches from the
> host-provided page-table to the new one, and wraps up its
> initialization by enabling the new allocator, before returning to
> the host.
>
> 6. the host can free the now unused page-table created for EL2, and
> will now need to issue hypercalls to make changes to the EL2 stage 1
> mappings instead of modifying them directly.
>
> Note that for the sake of simplifying the review, this patch focuses on
> the hypervisor side of things. In other words, this only implements the
> new hypercalls, but does not make use of them from the host yet. The
> host-side changes will follow in a subsequent patch.
>
> Credits to Will for __pkvm_init_switch_pgd.
>
> Co-authored-by: Will Deacon <will@kernel.org>
> Signed-off-by: Will Deacon <will@kernel.org>
> Signed-off-by: Quentin Perret <qperret@google.com>
> ---
> arch/arm64/include/asm/kvm_asm.h | 4 +
> arch/arm64/include/asm/kvm_host.h | 7 +
> arch/arm64/include/asm/kvm_hyp.h | 8 ++
> arch/arm64/include/asm/kvm_pgtable.h | 2 +
> arch/arm64/kernel/image-vars.h | 16 +++
> arch/arm64/kvm/hyp/Makefile | 2 +-
> arch/arm64/kvm/hyp/include/nvhe/mm.h | 71 ++++++++++
> arch/arm64/kvm/hyp/nvhe/Makefile | 4 +-
> arch/arm64/kvm/hyp/nvhe/hyp-init.S | 27 ++++
> arch/arm64/kvm/hyp/nvhe/hyp-main.c | 49 +++++++
> arch/arm64/kvm/hyp/nvhe/mm.c | 173 +++++++++++++++++++++++
> arch/arm64/kvm/hyp/nvhe/setup.c | 197 +++++++++++++++++++++++++++
> arch/arm64/kvm/hyp/pgtable.c | 2 -
> arch/arm64/kvm/hyp/reserved_mem.c | 92 +++++++++++++
> arch/arm64/mm/init.c | 3 +
> 15 files changed, 652 insertions(+), 5 deletions(-)
> create mode 100644 arch/arm64/kvm/hyp/include/nvhe/mm.h
> create mode 100644 arch/arm64/kvm/hyp/nvhe/mm.c
> create mode 100644 arch/arm64/kvm/hyp/nvhe/setup.c
> create mode 100644 arch/arm64/kvm/hyp/reserved_mem.c

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

Will

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