sync with 'master'

exa/exa_migration.c

@@ -153,22 +153,39 @@ exaCopyDirty(ExaMigrationPtr migrate, RegionPtr pValidDst, RegionPtr pValidSrc,
     REGION_SUBTRACT(pScreen, &CopyReg, pValidSrc, pValidDst);
 
     if (migrate->as_dst) {
-	RegionPtr pending_damage = DamagePendingRegion(pExaPixmap->pDamage);
+	ExaScreenPriv (pPixmap->drawable.pScreen);
 
-	if (REGION_NIL(pending_damage)) {
-	    static Bool firsttime = TRUE;
+	/* XXX: The pending damage region will be marked as damaged after the
+	 * operation, so it should serve as an upper bound for the region that
+	 * needs to be synchronized for the operation. Unfortunately, this
+	 * causes corruption in some cases, e.g. when starting compiz. See
+	 * https://bugs.freedesktop.org/show_bug.cgi?id=12916 .
+	 */
+	if (pExaScr->optimize_migration) {
+	    RegionPtr pending_damage = DamagePendingRegion(pExaPixmap->pDamage);
+
+	    if (REGION_NIL(pending_damage)) {
+		static Bool firsttime = TRUE;
 
-	    if (firsttime) {
-		ErrorF("%s: Pending damage region empty!\n", __func__);
-		firsttime = FALSE;
+		if (firsttime) {
+		    ErrorF("%s: Pending damage region empty!\n", __func__);
+		    firsttime = FALSE;
+		}
 	    }
-	}
 
-	REGION_INTERSECT(pScreen, &CopyReg, &CopyReg, pending_damage);
+	    REGION_INTERSECT(pScreen, &CopyReg, &CopyReg, pending_damage);
+	}
 
+	/* The caller may provide a region to be subtracted from the calculated
+	 * dirty region. This is to avoid migration of bits that don't
+	 * contribute to the result of the operation.
+	 */
 	if (migrate->pReg)
 	    REGION_SUBTRACT(pScreen, &CopyReg, &CopyReg, migrate->pReg);
     } else {
+	/* The caller may restrict the region to be migrated for source pixmaps
+	 * to what's relevant for the operation.
+	 */
 	if (migrate->pReg)
 	    REGION_INTERSECT(pScreen, &CopyReg, &CopyReg, migrate->pReg);
     }

exa/exa_priv.h

@@ -119,6 +119,7 @@ typedef struct {
     enum ExaMigrationHeuristic	 migration;
     Bool			 checkDirtyCorrectness;
     unsigned			 disableFbCount;
+    Bool			 optimize_migration;
 } ExaScreenPrivRec, *ExaScreenPrivPtr;
 
 /*

hw/xfree86/exa/exa.man.pre

@@ -31,6 +31,12 @@ Disables acceleration of downloading of pixmap data from the framebuffer.
 Not usable with drivers which rely on DownloadFromScreen succeeding.
 Default: No.
 .TP
+.BI "Option \*qEXAOptimizeMigration\*q \*q" boolean \*q
+Enables an additional optimization for migration of destination pixmaps. This
+may improve performance in some cases (e.g. when switching virtual desktops with
+no compositing manager) but causes corruption in others (e.g. when starting
+compiz). Default: No.
+.TP
 .BI "Option \*qMigrationHeuristic\*q \*q" anystr \*q
 Chooses an alternate pixmap migration heuristic, for debugging purposes.  The
 default is intended to be the best performing one for general use, though others

hw/xfree86/exa/examodule.c

@@ -50,6 +50,7 @@ typedef enum {
     EXAOPT_NO_COMPOSITE,
     EXAOPT_NO_UTS,
     EXAOPT_NO_DFS,
+    EXAOPT_OPTIMIZE_MIGRATION
 } EXAOpts;
 
 static const OptionInfoRec EXAOptions[] = {
@@ -61,6 +62,8 @@ static const OptionInfoRec EXAOptions[] = {
 				OPTV_BOOLEAN,	{0}, FALSE },
     { EXAOPT_NO_DFS,			"EXANoDownloadFromScreen",
 				OPTV_BOOLEAN,	{0}, FALSE },
+    { EXAOPT_OPTIMIZE_MIGRATION,	"EXAOptimizeMigration",
+				OPTV_BOOLEAN,	{0}, FALSE },
     { -1,				NULL,
 				OPTV_NONE,	{0}, FALSE }
 };
@@ -144,6 +147,11 @@ exaDDXDriverInit(ScreenPtr pScreen)
 			    heuristicName);
 	    }
 	}
+
+	pExaScr->optimize_migration =
+	    xf86ReturnOptValBool(pScreenPriv->options,
+				 EXAOPT_OPTIMIZE_MIGRATION,
+				 FALSE);
     }
 
     if (xf86IsOptionSet(pScreenPriv->options, EXAOPT_NO_COMPOSITE)) {