Changeset 88536 in vbox for trunk/src/VBox/Devices/Serial

Timestamp:

Apr 15, 2021 12:21:11 PM (4 years ago)

Author:

vboxsync

svn:sync-xref-src-repo-rev:

143812

Message:

Devices/Serial/UartCore: Update the interrupt level everytime the internal interrupt state is updated to avoid the guest losing interrupts for an ISA serial device where the guest expects an edge triggered interrupt

File:

• trunk/src/VBox/Devices/Serial/UartCore.cpp (modified) (1 diff)

trunk/src/VBox/Devices/Serial/UartCore.cpp

@@ -315 +315 @@
     LogFlowFunc(("    uRegIirNew=%#x uRegIir=%#x\n", uRegIirNew, pThis->uRegIir));
 
-    /* Change interrupt only if the interrupt status really changed from the previous value. */
     if (uRegIirNew != (pThis->uRegIir & UART_REG_IIR_CHANGED_MASK))
-    {
         LogFlow(("    Interrupt source changed from %#x -> %#x (IRQ %d -> %d)\n",
                  pThis->uRegIir, uRegIirNew,
                  pThis->uRegIir == UART_REG_IIR_IP_NO_INT ? 0 : 1,
                  uRegIirNew == UART_REG_IIR_IP_NO_INT ? 0 : 1));
-        if (uRegIirNew == UART_REG_IIR_IP_NO_INT)
-            pThisCC->pfnUartIrqReq(pDevIns, pThis, pThis->iLUN, 0);
-        else
-            pThisCC->pfnUartIrqReq(pDevIns, pThis, pThis->iLUN, 1);
-    }
     else
         LogFlow(("    No change in interrupt source\n"));
+
+    /*
+     * Set interrupt value accordingly. As this is an ISA device most guests
+     * configure the IRQ as edge triggered instead of level triggered.
+     * So this needs to be done everytime, even if the internal interrupt state
+     * doesn't change in order to avoid the guest losing interrupts (reading one byte at
+     * a time from the FIFO for instance which doesn't change the interrupt source).
+     */
+    if (uRegIirNew == UART_REG_IIR_IP_NO_INT)
+        pThisCC->pfnUartIrqReq(pDevIns, pThis, pThis->iLUN, 0);
+    else
+        pThisCC->pfnUartIrqReq(pDevIns, pThis, pThis->iLUN, 1);
 
     if (pThis->uRegFcr & UART_REG_FCR_FIFO_EN)