KVM: arm64: Drop pkvm_mem_transition for FF-A

Simplify the __pkvm_host_{un}share_ffa() paths by using
{check,set}_page_state_range().

No functional changes intended.

Signed-off-by: Quentin Perret <qperret@google.com>
Link: https://lore.kernel.org/r/20250110121936.1559655-2-qperret@google.com
Signed-off-by: Marc Zyngier <maz@kernel.org>

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

@@ -1324,45 +1324,29 @@ void hyp_unpin_shared_mem(void *from, void *to)
 
 int __pkvm_host_share_ffa(u64 pfn, u64 nr_pages)
 {
+	u64 phys = hyp_pfn_to_phys(pfn);
+	u64 size = PAGE_SIZE * nr_pages;
 	int ret;
-	struct pkvm_mem_share share = {
-		.tx	= {
-			.nr_pages	= nr_pages,
-			.initiator	= {
-				.id	= PKVM_ID_HOST,
-				.addr	= hyp_pfn_to_phys(pfn),
-			},
-			.completer	= {
-				.id	= PKVM_ID_FFA,
-			},
-		},
-	};
 
 	host_lock_component();
-	ret = do_share(&share);
+	ret = __host_check_page_state_range(phys, size, PKVM_PAGE_OWNED);
+	if (!ret)
+		ret = __host_set_page_state_range(phys, size, PKVM_PAGE_SHARED_OWNED);
 	host_unlock_component();
 
 	return ret;
 }
 
 int __pkvm_host_unshare_ffa(u64 pfn, u64 nr_pages)
 {
+	u64 phys = hyp_pfn_to_phys(pfn);
+	u64 size = PAGE_SIZE * nr_pages;
 	int ret;
-	struct pkvm_mem_share share = {
-		.tx	= {
-			.nr_pages	= nr_pages,
-			.initiator	= {
-				.id	= PKVM_ID_HOST,
-				.addr	= hyp_pfn_to_phys(pfn),
-			},
-			.completer	= {
-				.id	= PKVM_ID_FFA,
-			},
-		},
-	};
 
 	host_lock_component();
-	ret = do_unshare(&share);
+	ret = __host_check_page_state_range(phys, size, PKVM_PAGE_SHARED_OWNED);
+	if (!ret)
+		ret = __host_set_page_state_range(phys, size, PKVM_PAGE_OWNED);
 	host_unlock_component();
 
 	return ret;