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KVM: arm64: Restrict EL2 stage-1 changes in protected mode

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The host kernel is currently able to change EL2 stage-1 mappings without
restrictions thanks to the __pkvm_create_mappings() hypercall. But in a
world where the host is no longer part of the TCB, this clearly poses a
problem.

To fix this, introduce a new hypercall to allow the host to share a
physical memory page with the hypervisor, and remove the
__pkvm_create_mappings() variant. The new hypercall implements
ownership and permission checks before allowing the sharing operation,
and it annotates the shared page in the hypervisor stage-1 and host
stage-2 page-tables.

Signed-off-by: Quentin Perret <qperret@google.com>
Reviewed-by: Fuad Tabba <tabba@google.com>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20210809152448.1810400-21-qperret@google.com
This commit is contained in:
Quentin Perret
2021-08-09 16:24:47 +01:00
committed by Marc Zyngier
parent f9370010e9
commit 66c57edd3b
5 changed files with 118 additions and 12 deletions
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1
arch/arm64/kvm/hyp/include/nvhe/mem_protect.h
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@@ -49,6 +49,7 @@ extern struct host_kvm host_kvm;
extern const u8 pkvm_hyp_id;
int __pkvm_prot_finalize(void);
int __pkvm_host_share_hyp(u64 pfn);
bool addr_is_memory(phys_addr_t phys);
int host_stage2_idmap_locked(phys_addr_t addr, u64 size, enum kvm_pgtable_prot prot);