drm/amd/display: System crashes when add_ptb_to_table() gets called

[Why]
Unused VMIDs were not evicted correctly

[How]
1. evict_vmids() logic was fixed;
2. Added boundary check for add_ptb_to_table() and
   clear_entry_from_vmid_table() to avoid crash caused by array out of
   boundary;
3. For mod_vmid_get_for_ptb(), vimd is changed from unsigned to signed
   due to vimd is signed.

Signed-off-by: Peikang Zhang <peikang.zhang@amd.com>
Reviewed-by: Aric Cyr <Aric.Cyr@amd.com>
Acked-by: Rodrigo Siqueira <Rodrigo.Siqueira@amd.com>
Acked-by: Harry Wentland <harry.wentland@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/display/modules/vmid/vmid.c

@@ -40,14 +40,18 @@ struct core_vmid {
 
 static void add_ptb_to_table(struct core_vmid *core_vmid, unsigned int vmid, uint64_t ptb)
 {
-	core_vmid->ptb_assigned_to_vmid[vmid] = ptb;
-	core_vmid->num_vmids_available--;
+	if (vmid < MAX_VMID) {
+		core_vmid->ptb_assigned_to_vmid[vmid] = ptb;
+		core_vmid->num_vmids_available--;
+	}
 }
 
 static void clear_entry_from_vmid_table(struct core_vmid *core_vmid, unsigned int vmid)
 {
-	core_vmid->ptb_assigned_to_vmid[vmid] = 0;
-	core_vmid->num_vmids_available++;
+	if (vmid < MAX_VMID) {
+		core_vmid->ptb_assigned_to_vmid[vmid] = 0;
+		core_vmid->num_vmids_available++;
+	}
 }
 
 static void evict_vmids(struct core_vmid *core_vmid)
@@ -57,7 +61,7 @@ static void evict_vmids(struct core_vmid *core_vmid)
 
 	// At this point any positions with value 0 are unused vmids, evict them
 	for (i = 1; i < core_vmid->num_vmid; i++) {
-		if (ord & (1u << i))
+		if (!(ord & (1u << i)))
 			clear_entry_from_vmid_table(core_vmid, i);
 	}
 }
@@ -91,7 +95,7 @@ static int get_next_available_vmid(struct core_vmid *core_vmid)
 uint8_t mod_vmid_get_for_ptb(struct mod_vmid *mod_vmid, uint64_t ptb)
 {
 	struct core_vmid *core_vmid = MOD_VMID_TO_CORE(mod_vmid);
-	unsigned int vmid = 0;
+	int vmid = 0;
 
 	// Physical address gets vmid 0
 	if (ptb == 0)