[PATCH v4 4/4] via-ide: Also emulate non 100% native mode

[BALATON Zoltan]

Some machines operate in "non 100% native mode" where interrupts are
fixed at legacy IDE interrupts and some guests expect this behaviour
without checking based on knowledge about hardware. Even Linux has
arch specific workarounds for this that are activated on such boards
so this needs to be emulated as well.

Signed-off-by: BALATON Zoltan <bala...@eik.bme.hu>
---

Notes:
    v2: Don't use PCI_INTERRUPT_LINE in via_ide_set_irq()
    v3: Patch pci.c instead of local workaround for PCI reset clearing
        PCI_INTERRUPT_PIN config reg

 hw/ide/via.c | 30 ++++++++++++++++++++++++------
 1 file changed, 24 insertions(+), 6 deletions(-)

diff --git a/hw/ide/via.c b/hw/ide/via.c
index df0b352b58..1eada23097 100644
--- a/hw/ide/via.c
+++ b/hw/ide/via.c
@@ -1,9 +1,10 @@
 /*
- * QEMU IDE Emulation: PCI VIA82C686B support.
+ * QEMU VIA southbridge IDE emulation (VT82C686B, VT8231)
  *
  * Copyright (c) 2003 Fabrice Bellard
  * Copyright (c) 2006 Openedhand Ltd.
  * Copyright (c) 2010 Huacai Chen <zltjiang...@gmail.com>
+ * Copyright (c) 2019-2020 BALATON Zoltan
  *
  * Permission is hereby granted, free of charge, to any person obtaining a copy
  * of this software and associated documentation files (the "Software"), to 
deal
@@ -25,6 +26,7 @@
  */
 
 #include "qemu/osdep.h"
+#include "hw/qdev-properties.h"
 #include "hw/pci/pci.h"
 #include "migration/vmstate.h"
 #include "qemu/module.h"
@@ -111,11 +113,18 @@ static void via_ide_set_irq(void *opaque, int n, int 
level)
     } else {
         d->config[0x70 + n * 8] &= ~0x80;
     }
-
     level = (d->config[0x70] & 0x80) || (d->config[0x78] & 0x80);
-    n = pci_get_byte(d->config + PCI_INTERRUPT_LINE);
-    if (n) {
-        qemu_set_irq(isa_get_irq(NULL, n), level);
+
+    /*
+     * Some machines operate in "non 100% native mode" where PCI_INTERRUPT_LINE
+     * is not used but IDE always uses ISA IRQ 14 and 15 even in native mode.
+     * Some guest drivers expect this, often without checking.
+     */
+    if (!(pci_get_byte(d->config + PCI_CLASS_PROG) & (n ? 4 : 1)) ||
+        PCI_IDE(d)->flags & BIT(PCI_IDE_LEGACY_IRQ)) {
+        qemu_set_irq(isa_get_irq(NULL, (n ? 15 : 14)), level);
+    } else {
+        qemu_set_irq(isa_get_irq(NULL, 14), level);
     }
 }
 
@@ -169,7 +178,9 @@ static void via_ide_realize(PCIDevice *dev, Error **errp)
 
     pci_config_set_prog_interface(pci_conf, 0x8f); /* native PCI ATA mode */
     pci_set_long(pci_conf + PCI_CAPABILITY_LIST, 0x000000c0);
-    dev->wmask[PCI_INTERRUPT_LINE] = 0xf;
+    /* Bits 0 and 4 of CLASS_PROG select native mode and are writable */
+    dev->wmask[PCI_CLASS_PROG] = 5;
+    dev->wmask[PCI_INTERRUPT_LINE] = 0;
 
     memory_region_init_io(&d->data_bar[0], OBJECT(d), &pci_ide_data_le_ops,
                           &d->bus[0], "via-ide0-data", 8);
@@ -213,6 +224,12 @@ static void via_ide_exitfn(PCIDevice *dev)
     }
 }
 
+static Property via_ide_properties[] = {
+    DEFINE_PROP_BIT("legacy-irq", PCIIDEState, flags, PCI_IDE_LEGACY_IRQ,
+                    false),
+    DEFINE_PROP_END_OF_LIST(),
+};
+
 static void via_ide_class_init(ObjectClass *klass, void *data)
 {
     DeviceClass *dc = DEVICE_CLASS(klass);
@@ -225,6 +242,7 @@ static void via_ide_class_init(ObjectClass *klass, void 
*data)
     k->device_id = PCI_DEVICE_ID_VIA_IDE;
     k->revision = 0x06;
     k->class_id = PCI_CLASS_STORAGE_IDE;
+    device_class_set_props(dc, via_ide_properties);
     set_bit(DEVICE_CATEGORY_STORAGE, dc->categories);
 }
 
-- 
2.21.1