KVM: arm64: Fix the descriptor address in __kvm_at_swap_desc()

Using "(u64 __user *)hva + offset" to get the virtual addresses of S1/S2
descriptors looks really wrong, if offset is not zero. What we want to get
for swapping is hva + offset, not hva + offset*8. ;-)

Fix it.

Fixes: f6927b4 ("KVM: arm64: Add helper for swapping guest descriptor")
Signed-off-by: Zenghui Yu (Huawei) <[email protected]>
Link: https://patch.msgid.link/[email protected]
Signed-off-by: Marc Zyngier <[email protected]>
Cc: [email protected]

Author: Zenghui Yu (Huawei)

arch/arm64/kvm/at.c

@@ -1753,7 +1753,7 @@ int __kvm_at_swap_desc(struct kvm *kvm, gpa_t ipa, u64 old, u64 new)
 	if (!writable)
 		return -EPERM;
 
-	ptep = (u64 __user *)hva + offset;
+	ptep = (void __user *)hva + offset;
 	if (cpus_have_final_cap(ARM64_HAS_LSE_ATOMICS))
 		r = __lse_swap_desc(ptep, old, new);
 	else