[PATCH] hw/scsi/lsi53c895a: add timer to scripts processing

[Sven Schnelle <svens@stackframe.org>]

Some OS's like HP-UX 10.20 are spinn

HP-UX 10.20 seems to make the lsi53c895a spinning on a memory location
under certain circumstances. As the SCSI controller and CPU are not
running at the same time this loop will never finish. After some
time, the check loop interrupts with a unexpected device disconnect.
This works, but is slow because the kernel resets the scsi controller.
Instead of signaling UDC, start a timer and exit the loop. Until the
timer fires, the CPU can process instructions until the timer fires.
The limit of instructions is also reduced because scripts running
on the SCSI processor are usually very short. This keeps the time
until the loop-exit short.

Suggested-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Sven Schnelle <svens@stackframe.org>
---
 hw/scsi/lsi53c895a.c | 33 +++++++++++++++++++++++++--------
 1 file changed, 25 insertions(+), 8 deletions(-)

diff --git a/hw/scsi/lsi53c895a.c b/hw/scsi/lsi53c895a.c
index d607a5f9fb..0b6f1dc72f 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);
@@ -1152,13 +1161,8 @@ 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 +2201,9 @@ 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 +2301,15 @@ 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 +2329,7 @@ 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
-- 
2.43.2