hw/i386: Deprecate -drive if=scsi with PC machine types

The PC machines (pc-q35-* pc-i440fx-* pc-* isapc xenfv) automatically
create lsi53c895a SCSI HBAs and SCSI devices to honor -drive if=scsi.
For giggles, try -drive if=scsi,bus=25,media=cdrom --- this makes QEMU
create 25 of them.

lsi53c895a is thoroughly obsolete (PCI Ultra2 SCSI, ca. 2000), and
currently has no maintainer in QEMU.  megasas is a better choice,
except with old OSes that lack drivers.  virtio-scsi is a much better
choice when you have a driver, but only (newish) Linux comes with one
in the box.  There is no good default that works for all guests.

Encourage users to pick a non-obsolete SCSI HBA that works for them by
deprecating -drive if=scsi.

Signed-off-by: Markus Armbruster <armbru@redhat.com>
Message-Id: <1487161136-9018-4-git-send-email-armbru@redhat.com>
Acked-By: Paolo Bonzini <pbonzini@redhat.com>

hw/i386/pc.c

@@ -1650,9 +1650,15 @@ void pc_pci_device_init(PCIBus *pci_bus)
     int max_bus;
     int bus;
 
+    /* Note: if=scsi is deprecated with PC machine types */
     max_bus = drive_get_max_bus(IF_SCSI);
     for (bus = 0; bus <= max_bus; bus++) {
-        lsi53c895a_create(pci_bus);
+        pci_create_simple(pci_bus, -1, "lsi53c895a");
+        /*
+         * By not creating frontends here, we make
+         * scsi_legacy_handle_cmdline() create them, and warn that
+         * this usage is deprecated.
+         */
     }
 }
 

qemu-options.hx

@@ -654,11 +654,6 @@ If you don't specify the "file=" argument, you define an empty drive:
 qemu-system-i386 -drive if=ide,index=1,media=cdrom
 @end example
 
-You can connect a SCSI disk with unit ID 6 on the bus #0:
-@example
-qemu-system-i386 -drive file=file,if=scsi,bus=0,unit=6
-@end example
-
 Instead of @option{-fda}, @option{-fdb}, you can use:
 @example
 qemu-system-i386 -drive file=file,index=0,if=floppy

tests/qemu-iotests/051.pc.out

@@ -118,7 +118,8 @@ QEMU X.Y.Z monitor - type 'help' for more information
 
 Testing: -drive if=scsi,media=cdrom
 QEMU X.Y.Z monitor - type 'help' for more information
-(qemu) qququiquit
+(qemu) QEMU_PROG: -drive if=scsi,media=cdrom: warning: bus=0,unit=0 is deprecated with this machine type
+qququiquit
 
 Testing: -drive if=ide
 QEMU X.Y.Z monitor - type 'help' for more information
@@ -127,7 +128,8 @@ QEMU_PROG: Initialization of device ide-hd failed: Device initialization failed.
 
 Testing: -drive if=scsi
 QEMU X.Y.Z monitor - type 'help' for more information
-(qemu) QEMU_PROG: Initialization of device lsi53c895a failed: Device needs media, but drive is empty
+(qemu) QEMU_PROG: -drive if=scsi: warning: bus=0,unit=0 is deprecated with this machine type
+QEMU_PROG: -drive if=scsi: Device needs media, but drive is empty
 
 Testing: -drive if=virtio
 QEMU X.Y.Z monitor - type 'help' for more information
@@ -172,7 +174,8 @@ QEMU X.Y.Z monitor - type 'help' for more information
 
 Testing: -drive file=TEST_DIR/t.qcow2,if=scsi,media=cdrom,readonly=on
 QEMU X.Y.Z monitor - type 'help' for more information
-(qemu) qququiquit
+(qemu) QEMU_PROG: -drive file=TEST_DIR/t.qcow2,if=scsi,media=cdrom,readonly=on: warning: bus=0,unit=0 is deprecated with this machine type
+qququiquit
 
 Testing: -drive file=TEST_DIR/t.qcow2,if=ide,readonly=on
 QEMU X.Y.Z monitor - type 'help' for more information
@@ -181,7 +184,8 @@ QEMU_PROG: Initialization of device ide-hd failed: Device initialization failed.
 
 Testing: -drive file=TEST_DIR/t.qcow2,if=scsi,readonly=on
 QEMU X.Y.Z monitor - type 'help' for more information
-(qemu) qququiquit
+(qemu) QEMU_PROG: -drive file=TEST_DIR/t.qcow2,if=scsi,readonly=on: warning: bus=0,unit=0 is deprecated with this machine type
+qququiquit
 
 Testing: -drive file=TEST_DIR/t.qcow2,if=virtio,readonly=on
 QEMU X.Y.Z monitor - type 'help' for more information