1 files changed, 33 insertions, 10 deletions

diff --git a/hw/scsi/lsi53c895a.c b/hw/scsi/lsi53c895a.c
index d607a5f9fb..4ff9470381 100644
--- a/hw/scsi/lsi53c895a.c
+++ b/hw/scsi/lsi53c895a.c
@@ -188,7 +188,7 @@ static const char *names[] = {
 #define LSI_TAG_VALID     (1 << 16)
 
 /* Maximum instructions to process. */
-#define LSI_MAX_INSN    10000
+#define LSI_MAX_INSN    100
 
 typedef struct lsi_request {
     SCSIRequest *req;
@@ -205,6 +205,7 @@ enum {
     LSI_WAIT_RESELECT, /* Wait Reselect instruction has been issued */
     LSI_DMA_SCRIPTS, /* processing DMA from lsi_execute_script */
     LSI_DMA_IN_PROGRESS, /* DMA operation is in progress */
+    LSI_WAIT_SCRIPTS, /* SCRIPTS stopped because of instruction count limit */
 };
 
 enum {
@@ -224,6 +225,7 @@ struct LSIState {
     MemoryRegion ram_io;
     MemoryRegion io_io;
     AddressSpace pci_io_as;
+    QEMUTimer *scripts_timer;
 
     int carry; /* ??? Should this be an a visible register somewhere?  */
     int status;
@@ -415,6 +417,7 @@ static void lsi_soft_reset(LSIState *s)
     s->sbr = 0;
     assert(QTAILQ_EMPTY(&s->queue));
     assert(!s->current);
+    timer_del(s->scripts_timer);
 }
 
 static int lsi_dma_40bit(LSIState *s)
@@ -1127,6 +1130,12 @@ static void lsi_wait_reselect(LSIState *s)
     }
 }
 
+static void lsi_scripts_timer_start(LSIState *s)
+{
+    trace_lsi_scripts_timer_start();
+    timer_mod(s->scripts_timer, qemu_clock_get_us(QEMU_CLOCK_VIRTUAL) + 500);
+}
+
 static void lsi_execute_script(LSIState *s)
 {
     PCIDevice *pci_dev = PCI_DEVICE(s);
@@ -1136,6 +1145,11 @@ static void lsi_execute_script(LSIState *s)
     int insn_processed = 0;
     static int reentrancy_level;
 
+    if (s->waiting == LSI_WAIT_SCRIPTS) {
+        timer_del(s->scripts_timer);
+        s->waiting = LSI_NOWAIT;
+    }
+
     reentrancy_level++;
 
     s->istat1 |= LSI_ISTAT1_SRUN;
@@ -1143,8 +1157,8 @@ again:
     /*
      * Some windows drivers make the device spin waiting for a memory location
      * to change. If we have executed more than LSI_MAX_INSN instructions then
-     * assume this is the case and force an unexpected device disconnect. This
-     * is apparently sufficient to beat the drivers into submission.
+     * assume this is the case and start a timer. Until the timer fires, the
+     * host CPU has a chance to run and change the memory location.
      *
      * Another issue (CVE-2023-0330) can occur if the script is programmed to
      * trigger itself again and again. Avoid this problem by stopping after
@@ -1152,13 +1166,8 @@ again:
      * which should be enough for all valid use cases).
      */
     if (++insn_processed > LSI_MAX_INSN || reentrancy_level > 8) {
-        if (!(s->sien0 & LSI_SIST0_UDC)) {
-            qemu_log_mask(LOG_GUEST_ERROR,
-                          "lsi_scsi: inf. loop with UDC masked");
-        }
-        lsi_script_scsi_interrupt(s, LSI_SIST0_UDC, 0);
-        lsi_disconnect(s);
-        trace_lsi_execute_script_stop();
+        s->waiting = LSI_WAIT_SCRIPTS;
+        lsi_scripts_timer_start(s);
         reentrancy_level--;
         return;
     }
@@ -2197,6 +2206,9 @@ static int lsi_post_load(void *opaque, int version_id)
         return -EINVAL;
     }
 
+    if (s->waiting == LSI_WAIT_SCRIPTS) {
+        lsi_scripts_timer_start(s);
+    }
     return 0;
 }
 
@@ -2294,6 +2306,15 @@ static const struct SCSIBusInfo lsi_scsi_info = {
     .cancel = lsi_request_cancelled
 };
 
+static void scripts_timer_cb(void *opaque)
+{
+    LSIState *s = opaque;
+
+    trace_lsi_scripts_timer_triggered();
+    s->waiting = LSI_NOWAIT;
+    lsi_execute_script(s);
+}
+
 static void lsi_scsi_realize(PCIDevice *dev, Error **errp)
 {
     LSIState *s = LSI53C895A(dev);
@@ -2313,6 +2334,7 @@ static void lsi_scsi_realize(PCIDevice *dev, Error **errp)
                           "lsi-ram", 0x2000);
     memory_region_init_io(&s->io_io, OBJECT(s), &lsi_io_ops, s,
                           "lsi-io", 256);
+    s->scripts_timer = timer_new_us(QEMU_CLOCK_VIRTUAL, scripts_timer_cb, s);
 
     /*
      * Since we use the address-space API to interact with ram_io, disable the
@@ -2337,6 +2359,7 @@ static void lsi_scsi_exit(PCIDevice *dev)
     LSIState *s = LSI53C895A(dev);
 
     address_space_destroy(&s->pci_io_as);
+    timer_del(s->scripts_timer);
 }
 
 static void lsi_class_init(ObjectClass *klass, void *data)