KVM: arm64: nv: Add basic emulation of AT S1E{0,1}{R,W}

Emulating AT instructions is one the tasks devolved to the host
hypervisor when NV is on.

Here, we take the basic approach of emulating AT S1E{0,1}{R,W}
using the AT instructions themselves. While this mostly work,
it doesn't *always* work:

- S1 page tables can be swapped out

- shadow S2 can be incomplete and not contain mappings for
  the S1 page tables

We are not trying to handle these case here, and defer it to
a later patch. Suitable comments indicate where we are in dire
need of better handling.

Co-developed-by: Jintack Lim <jintack.lim@linaro.org>
Signed-off-by: Jintack Lim <jintack.lim@linaro.org>
Signed-off-by: Marc Zyngier <maz@kernel.org>

1 files changed, 1 insertions, 0 deletions

diff --git a/arch/arm64/include/asm/kvm_asm.h b/arch/arm64/include/asm/kvm_asm.h
index 25f49f5fc4a6..9b6c9f4f4d88 100644
--- a/arch/arm64/include/asm/kvm_asm.h
+++ b/arch/arm64/include/asm/kvm_asm.h
@@ -236,6 +236,7 @@ extern void __kvm_tlb_flush_vmid(struct kvm_s2_mmu *mmu);
 extern int __kvm_tlbi_s1e2(struct kvm_s2_mmu *mmu, u64 va, u64 sys_encoding);
 
 extern void __kvm_timer_set_cntvoff(u64 cntvoff);
+extern void __kvm_at_s1e01(struct kvm_vcpu *vcpu, u32 op, u64 vaddr);
 
 extern int __kvm_vcpu_run(struct kvm_vcpu *vcpu);