Changeset 105805 in vbox for trunk/src/VBox/VMM

Timestamp:

Aug 21, 2024 11:52:56 PM (5 months ago)

Author:

vboxsync

Message:

VMM/IEM: End TB if we get back to the first instruction again via an indirect route, e.g. jumping to a point before the TB starts, and optimize this using the loop-jump (todo 14). bugref:10720 bugref:10656

Location:

trunk/src/VBox/VMM

Files:

• VMMAll/IEMAllThrdRecompiler.cpp (modified) (2 diffs)
• VMMAll/IEMAllThrdTables.h (modified) (2 diffs)
• VMMR3/IEMR3.cpp (modified) (1 diff)
• include/IEMInternal.h (modified) (3 diffs)

trunk/src/VBox/VMM/VMMAll/IEMAllThrdRecompiler.cpp

@@ -2119 +2119 @@
 }
 
-
 #ifdef IEM_WITH_INTRA_TB_JUMPS
+
 /**
  * Emits the necessary tail calls for a full TB loop-jump.
@@ -2171 +2171 @@
     return false;
 }
+
+/**
+ * Called by IEM_MC2_BEGIN_EMIT_CALLS when it detects that we're back at the
+ * first instruction and we didn't just branch to it (that's handled below).
+ *
+ * This will emit a loop iff everything is compatible with that.
+ */
+DECLHIDDEN(int) iemThreadedCompileBackAtFirstInstruction(PVMCPU pVCpu, PIEMTB pTb) RT_NOEXCEPT
+{
+    /* Check if the mode matches. */
+    if (   (pVCpu->iem.s.fExec & IEMTB_F_IEM_F_MASK & IEMTB_F_KEY_MASK)
+        == (pTb->fFlags        & IEMTB_F_KEY_MASK   & ~IEMTB_F_CS_LIM_CHECKS))
+    {
+        STAM_REL_COUNTER_INC(&pVCpu->iem.s.StatTbLoopFullTbDetected2);
+        iemThreadedCompileFullTbJump(pVCpu, pTb);
+    }
+    return VINF_IEM_RECOMPILE_END_TB;
+}
+
 #endif /* IEM_WITH_INTRA_TB_JUMPS */
 

trunk/src/VBox/VMM/VMMAll/IEMAllThrdTables.h

@@ -174 +174 @@
 
 
+#ifndef IEM_WITH_INTRA_TB_JUMPS
+/**
+ * Stub for a no-jumps config, see IEMAllThrdRecompiler.cpp for the real thing.
+ */
+DECL_FORCE_INLINE(int) iemThreadedCompileBackAtFirstInstruction(PVMCPU pVCpu, PIEMTB pTb)
+{
+    RT_NOREF(pTb);
+    STAM_REL_COUNTER_INC(&pVCpu->iem.s.StatTbLoopFullTbDetected2);
+    return VINF_IEM_RECOMPILE_END_TB;
+}
+#endif
+
+
 /*
  * Emit call macros.
@@ -205 +218 @@
             && !(pTb->fFlags & IEMTB_F_CS_LIM_CHECKS)) \
         { \
-            /** @todo Custom copy function, given range is 1 thru 15 bytes. */ \
-            memcpy(&pTb->pabOpcodes[offOpcodeMc2], pVCpu->iem.s.abOpcode, pVCpu->iem.s.offOpcode); \
-            pTb->cbOpcodes                       = offOpcodeMc2 + pVCpu->iem.s.offOpcode; \
-            pTb->aRanges[idxRangeMc2].cbOpcodes += cbInstrMc2; \
-            Assert(pTb->cbOpcodes <= pVCpu->iem.s.cbOpcodesAllocated); \
+            /* Break/loop if we're back to the first instruction in the TB again. */ \
+            if (   pTb->aRanges[idxRangeMc2].idxPhysPage != 0 \
+                ||    (unsigned)pTb->aRanges[idxRangeMc2].offPhysPage + (unsigned)pTb->aRanges[idxRangeMc2].cbOpcodes \
+                   != (pTb->GCPhysPc & GUEST_PAGE_OFFSET_MASK) \
+                || offOpcodeMc2 == 0) \
+            { \
+                /** @todo Custom copy function, given range is 1 thru 15 bytes. */ \
+                memcpy(&pTb->pabOpcodes[offOpcodeMc2], pVCpu->iem.s.abOpcode, pVCpu->iem.s.offOpcode); \
+                pTb->cbOpcodes                       = offOpcodeMc2 + pVCpu->iem.s.offOpcode; \
+                pTb->aRanges[idxRangeMc2].cbOpcodes += cbInstrMc2; \
+                Assert(pTb->cbOpcodes <= pVCpu->iem.s.cbOpcodesAllocated); \
+            } \
+            else \
+                return iemThreadedCompileBackAtFirstInstruction(pVCpu, pTb); \
         } \
         else if (iemThreadedCompileBeginEmitCallsComplications(pVCpu, pTb)) \

trunk/src/VBox/VMM/VMMR3/IEMR3.cpp

@@ -686 +686 @@
         STAMR3RegisterF(pVM, (void *)&pVCpu->iem.s.StatTbLoopFullTbDetected, STAMTYPE_COUNTER, STAMVISIBILITY_ALWAYS, STAMUNIT_COUNT,
                         "Detected loop full TB",  "/IEM/CPU%u/re/LoopFullTbDetected", idCpu);
+        STAMR3RegisterF(pVM, (void *)&pVCpu->iem.s.StatTbLoopFullTbDetected2, STAMTYPE_COUNTER, STAMVISIBILITY_ALWAYS, STAMUNIT_COUNT,
+                        "Detected loop full TB but looping back to before the first TB instruction",
+                        "/IEM/CPU%u/re/LoopFullTbDetected2", idCpu);
         STAMR3RegisterF(pVM, (void *)&pVCpu->iem.s.StatTbLoopInTbDetected, STAMTYPE_COUNTER, STAMVISIBILITY_ALWAYS, STAMUNIT_COUNT,
                         "Detected loop within TB", "/IEM/CPU%u/re/LoopInTbDetected", idCpu);

trunk/src/VBox/VMM/include/IEMInternal.h

@@ -2295 +2295 @@
     /** Statistics: Times a loop back to the start of the TB was detected. */
     STAMCOUNTER             StatTbLoopFullTbDetected;
+    /** Statistics: Times a loop back to the start of the TB was detected, var 2. */
+    STAMCOUNTER             StatTbLoopFullTbDetected2;
     /** Exec memory allocator statistics: Number of times allocaintg executable memory failed. */
     STAMCOUNTER             StatNativeExecMemInstrBufAllocFailed;
@@ -2517 +2519 @@
 
 #ifdef IEM_WITH_TLB_TRACE
-    uint64_t                au64Padding[7];
+    uint64_t                au64Padding[6];
 #else
-    uint64_t                au64Padding[1];
+    //uint64_t                au64Padding[0];
 #endif
 
@@ -6884 +6886 @@
 bool iemThreadedCompileEmitIrqCheckBefore(PVMCPUCC pVCpu, PIEMTB pTb);
 bool iemThreadedCompileBeginEmitCallsComplications(PVMCPUCC pVCpu, PIEMTB pTb);
+#ifdef IEM_WITH_INTRA_TB_JUMPS
+DECLHIDDEN(int)     iemThreadedCompileBackAtFirstInstruction(PVMCPU pVCpu, PIEMTB pTb) RT_NOEXCEPT;
+#endif
 
 /* Native recompiler public bits: */