[PATCH] ide_ioport_read: Return lower octet of data register instead of 0xFF

[Lev Kujawski <lkujaw@member.fsf.org>]

Prior to this patch, the pre-GRUB Solaris x86 bootloader would fail to
load on QEMU with the following screen output:

SunOS Secondary Boot version 3.00

prom_panic: Could not mount filesystem.
Entering boot debugger:
[136419]: _

This occurs because the bootloader issues an ATA IDENTIFY DEVICE
command, and then reads the resulting 256 words of parameter
information using inb rather than the correct inw. As the previous
behavior of QEMU was to return 0xFF and not advance the drive's sector
buffer, DRQ would never be cleared and the bootloader would be blocked
from selecting a secondary ATA device, such as an optical drive.

Resolves:
* [Bug 1639394] Unable to boot Solaris 8/9 x86 under Fedora 24

Signed-off-by: Lev Kujawski <lkujaw@member.fsf.org>
---
 hw/ide/core.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/hw/ide/core.c b/hw/ide/core.c
index 3a5afff5d7..c2caa54285 100644
--- a/hw/ide/core.c
+++ b/hw/ide/core.c
@@ -2166,7 +2166,11 @@ uint32_t ide_ioport_read(void *opaque, uint32_t addr)
     hob = bus->cmd & (IDE_CTRL_HOB);
     switch (reg_num) {
     case ATA_IOPORT_RR_DATA:
-        ret = 0xff;
+        /*
+         * The pre-GRUB Solaris x86 bootloader relies upon inb
+         * consuming a word from the drive's sector buffer.
+         */
+        ret = ide_data_readw(bus, addr) & 0xff;
         break;
     case ATA_IOPORT_RR_ERROR:
         if ((!bus->ifs[0].blk && !bus->ifs[1].blk) ||
-- 
2.34.1