[PATCH v2 12/18] KVM: arm64: Filter out non-kernel addresses in kern_hyp_va

[Vincent Donnefort]

kern_hyp_va() is idempotent for the hypervisor linear space. This is
handy for nVHE hypervisor callers handling kvm_vcpu or kvm_arch
pointers. Those pointers can originate from the hypervisor space (when
protected mode is enabled, we don't trust the kernel and the hypervisor
uses its own copy) or from the kernel space (we do trust the kernel in
"non-protected" nVHE).

This idempotence does not hold for addresses within the hypervisor
private range, like the ones you get from the pKVM heap allocator
(hyp_alloc()). To resolve this, filter out non-kernel addresses based on
PAGE_OFFSET.

Leave the assembly version untouched as it has no current users.

Signed-off-by: Vincent Donnefort <vdonnefort at google.com>

diff --git a/arch/arm64/include/asm/kvm_mmu.h b/arch/arm64/include/asm/kvm_mmu.h
index 6eae7e7e2a68..d60e5f2de10c 100644
--- a/arch/arm64/include/asm/kvm_mmu.h
+++ b/arch/arm64/include/asm/kvm_mmu.h
@@ -126,6 +126,9 @@ static __always_inline unsigned long __kern_hyp_va(unsigned long v)
  * replace the instructions with `nop`s.
  */
 #ifndef __KVM_VHE_HYPERVISOR__
+	if (!is_ttbr1_addr(v))
+		return v;
+
 	asm volatile(ALTERNATIVE_CB("and %0, %0, #1\n"         /* mask with va_mask */
 				    "ror %0, %0, #1\n"         /* rotate to the first tag bit */
 				    "add %0, %0, #0\n"         /* insert the low 12 bits of the tag */
-- 
2.55.0.rc2.803.g1fd1e6609c-goog