fix(TLB): fix two issues in genVpn (#4647)

1. Level: Previously, the code always used the smaller value between
s1.stage and s2.stage, regardless of the virtualization stage. In fact,
only the allStage case should compare both stages; other cases should
determine the level independently based on their respective stage.

2. VPN: Previously, only the allStage case checked the level to decide
whether to concatenate the lower bits of the VPN. However, in reality,
other cases also need to perform VPN concatenation based on the level.

Author: good-circle

src/main/scala/xiangshan/cache/mmu/MMUBundle.scala

@@ -1291,15 +1291,24 @@ class PtwRespS2(implicit p: Parameters) extends PtwBundle {
   }
 
   def getVpn(vpn: UInt): UInt = {
-    val level = s1.entry.level.getOrElse(0.U) min s2.entry.level.getOrElse(0.U)
+    val level = MuxLookup(s2xlate, 0.U)(Seq(
+      onlyStage1 -> s1.entry.level.getOrElse(0.U),
+      onlyStage2 -> s2.entry.level.getOrElse(0.U),
+      allStage -> (s1.entry.level.getOrElse(0.U) min s2.entry.level.getOrElse(0.U)),
+      noS2xlate -> s1.entry.level.getOrElse(0.U)
+    ))
     val s1tag = Cat(s1.entry.tag, OHToUInt(s1.pteidx))
     val s1_vpn = MuxLookup(level, s1tag)(Seq(
       3.U -> Cat(s1.entry.tag(sectorvpnLen - 1, vpnnLen * 3 - sectortlbwidth), vpn(vpnnLen * 3 - 1, 0)),
       2.U -> Cat(s1.entry.tag(sectorvpnLen - 1, vpnnLen * 2 - sectortlbwidth), vpn(vpnnLen * 2 - 1, 0)),
       1.U -> Cat(s1.entry.tag(sectorvpnLen - 1, vpnnLen - sectortlbwidth), vpn(vpnnLen - 1, 0)))
     )
-    val s2_vpn = s2.entry.tag
-    Mux(s2xlate === onlyStage2, s2_vpn, Mux(s2xlate === allStage, s1_vpn, s1tag))
+    val s2_vpn = MuxLookup(level, s2.entry.tag)(Seq(
+      3.U -> Cat(s2.entry.tag(gvpnLen - 1, vpnnLen * 3), vpn(vpnnLen * 3 - 1, 0)),
+      2.U -> Cat(s2.entry.tag(gvpnLen - 1, vpnnLen * 2), vpn(vpnnLen * 2 - 1, 0)),
+      1.U -> Cat(s2.entry.tag(gvpnLen - 1, vpnnLen), vpn(vpnnLen - 1, 0)))
+    )
+    Mux(s2xlate === onlyStage2, s2_vpn, s1_vpn)
   }
 
   def hit(vpn: UInt, asid: UInt, vasid: UInt, vmid: UInt, allType: Boolean = false, ignoreAsid: Boolean = false): Bool = {