KVM: arm64: Introduce wrappers for host and hyp spin lock accessors

In preparation for adding additional locked sections for manipulating
page-tables at EL2, introduce some simple wrappers around the host and
hypervisor locks so that it's a bit easier to read and bit more difficult
to take the wrong lock (or even take them in the wrong order).
Signed-off-by: Will Deacon <will@kernel.org>
Signed-off-by: Quentin Perret <qperret@google.com>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20211215161232.1480836-10-qperret@google.com

arch/arm64/kvm/hyp/nvhe/mem_protect.c

@@ -27,6 +27,26 @@ static struct hyp_pool host_s2_pool;
 
 const u8 pkvm_hyp_id = 1;
 
+static void host_lock_component(void)
+{
+	hyp_spin_lock(&host_kvm.lock);
+}
+
+static void host_unlock_component(void)
+{
+	hyp_spin_unlock(&host_kvm.lock);
+}
+
+static void hyp_lock_component(void)
+{
+	hyp_spin_lock(&pkvm_pgd_lock);
+}
+
+static void hyp_unlock_component(void)
+{
+	hyp_spin_unlock(&pkvm_pgd_lock);
+}
+
 static void *host_s2_zalloc_pages_exact(size_t size)
 {
 	void *addr = hyp_alloc_pages(&host_s2_pool, get_order(size));
@@ -338,14 +358,14 @@ static int host_stage2_idmap(u64 addr)
 
 	prot = is_memory ? PKVM_HOST_MEM_PROT : PKVM_HOST_MMIO_PROT;
 
-	hyp_spin_lock(&host_kvm.lock);
+	host_lock_component();
 	ret = host_stage2_adjust_range(addr, &range);
 	if (ret)
 		goto unlock;
 
 	ret = host_stage2_idmap_locked(range.start, range.end - range.start, prot);
 unlock:
-	hyp_spin_unlock(&host_kvm.lock);
+	host_unlock_component();
 
 	return ret;
 }
@@ -369,8 +389,8 @@ int __pkvm_host_share_hyp(u64 pfn)
 	if (!addr_is_memory(addr))
 		return -EINVAL;
 
-	hyp_spin_lock(&host_kvm.lock);
-	hyp_spin_lock(&pkvm_pgd_lock);
+	host_lock_component();
+	hyp_lock_component();
 
 	ret = kvm_pgtable_get_leaf(&host_kvm.pgt, addr, &pte, NULL);
 	if (ret)
@@ -432,8 +452,8 @@ int __pkvm_host_share_hyp(u64 pfn)
 	BUG_ON(ret);
 
 unlock:
-	hyp_spin_unlock(&pkvm_pgd_lock);
-	hyp_spin_unlock(&host_kvm.lock);
+	hyp_unlock_component();
+	host_unlock_component();
 
 	return ret;
 }