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Date: Wed, 7 May 2008 20:02:06 -0300
From: Marcelo Tosatti <mtosatti@redhat.com>
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Subject: [Qemu-devel] LSI: avoid infinite loops
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To: Paul Brook <paul@codesourcery.com>
Cc: Alberto =?iso-8859-1?Q?Trevi=F1o?= <alberto@byu.edu>, qemu-devel@nongnu.org


The Windows driver has SCRIPTS code which busy loops on main memory. So
give the CPU's a chance to run if that happens.

Fixes
http://sourceforge.net/tracker/index.php?func=detail&aid=1895893&group_id=180599&atid=893831

Paul, I'm not conviced that a smarter algorithm to determine this
conditions is necessary... perhaps it would be wise to increase the
"200" magic number.

The scsi-disk.c patch in the bugzilla entry has been submitted but ignored.

diff --git a/qemu/hw/lsi53c895a.c b/qemu/hw/lsi53c895a.c
index 72ed5c3..2691418 100644
--- a/qemu/hw/lsi53c895a.c
+++ b/qemu/hw/lsi53c895a.c
@@ -840,9 +840,11 @@ static void lsi_execute_script(LSIState *s)
     uint32_t insn;
     uint32_t addr;
     int opcode;
+    int insns_processed = 0;
 
     s->istat1 |= LSI_ISTAT1_SRUN;
 again:
+    insns_processed++;
     insn = read_dword(s, s->dsp);
     addr = read_dword(s, s->dsp + 4);
     DPRINTF("SCRIPTS dsp=%08x opcode %08x arg %08x\n", s->dsp, insn, addr);
@@ -1197,8 +1199,13 @@ again:
             }
         }
     }
-    /* ??? Need to avoid infinite loops.  */
-    if (s->istat1 & LSI_ISTAT1_SRUN && !s->waiting) {
+    /*
+     * The Windows driver downloads SCRIPT code which busy loops 
+     * on main memory, so give the CPU's a chance to run if that
+     * happens.
+     */
+    if (insns_processed < 200 && s->istat1 & LSI_ISTAT1_SRUN &&
+       !s->waiting) {
         if (s->dcntl & LSI_DCNTL_SSM) {
             lsi_script_dma_interrupt(s, LSI_DSTAT_SSI);
         } else {