On Fri, Jan 08, 2021 at 12:15:24PM +0000, Quentin Perret wrote:

When KVM runs in protected nVHE mode, make use of a stage 2 page-table
to give the hypervisor some control over the host memory accesses. At
the moment all memory aborts from the host will be instantly idmapped
RWX at stage 2 in a lazy fashion. Later patches will make use of that
infrastructure to implement access control restrictions to e.g. protect
guest memory from the host.

Signed-off-by: Quentin Perret <redacted>
---
 arch/arm64/include/asm/kvm_cpufeature.h       |   2 +
 arch/arm64/kernel/image-vars.h                |   3 +
 arch/arm64/kvm/hyp/include/nvhe/mem_protect.h |  33 +++
 arch/arm64/kvm/hyp/nvhe/Makefile              |   2 +-
 arch/arm64/kvm/hyp/nvhe/hyp-init.S            |   1 +
 arch/arm64/kvm/hyp/nvhe/hyp-main.c            |   6 +
 arch/arm64/kvm/hyp/nvhe/mem_protect.c         | 191 ++++++++++++++++++
 arch/arm64/kvm/hyp/nvhe/setup.c               |   6 +
 arch/arm64/kvm/hyp/nvhe/switch.c              |   7 +-
 arch/arm64/kvm/hyp/nvhe/tlb.c                 |   4 +-
 10 files changed, 248 insertions(+), 7 deletions(-)
 create mode 100644 arch/arm64/kvm/hyp/include/nvhe/mem_protect.h
 create mode 100644 arch/arm64/kvm/hyp/nvhe/mem_protect.c

[...]

+void handle_host_mem_abort(struct kvm_cpu_context *host_ctxt)
+{
+	enum kvm_pgtable_prot prot;
+	u64 far, hpfar, esr, ipa;
+	int ret;
+
+	esr = read_sysreg_el2(SYS_ESR);
+	if (!__get_fault_info(esr, &far, &hpfar))
+		hyp_panic();
+
+	prot = KVM_PGTABLE_PROT_R | KVM_PGTABLE_PROT_W | KVM_PGTABLE_PROT_X;
+	ipa = (hpfar & HPFAR_MASK) << 8;
+	ret = host_stage2_map(ipa, PAGE_SIZE, prot);

Can we try to put down a block mapping if the whole thing falls within
memory?

Will

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