ahci: Implement HBA reset

The ahci code was missing its soft reset functionality. This wasn't really an
issue for Linux guests, but Windows gets confused when the controller doesn't
reset when it tells it so.

Using this patch I can now successfully boot Windows 7 from AHCI using AHCI
enabled SeaBIOS.
Signed-off-by: NAlexander Graf <agraf@suse.de>
Signed-off-by: NKevin Wolf <kwolf@redhat.com>

hw/ide/ahci.c

@@ -335,7 +335,7 @@ static void ahci_mem_writel(void *ptr, target_phys_addr_t addr, uint32_t val)
             case HOST_CTL: /* R/W */
                 if (val & HOST_CTL_RESET) {
                     DPRINTF(-1, "HBA Reset\n");
-                    /* FIXME reset? */
+                    ahci_reset(container_of(s, AHCIPCIState, ahci));
                 } else {
                     s->control_regs.ghc = (val & 0x3) | HOST_CTL_AHCI_EN;
                     ahci_check_irq(s);
@@ -1134,6 +1134,9 @@ void ahci_reset(void *opaque)
     struct AHCIPCIState *d = opaque;
     int i;
 
+    d->ahci.control_regs.irqstatus = 0;
+    d->ahci.control_regs.ghc = 0;
+
     for (i = 0; i < SATA_PORTS; i++) {
         ahci_reset_port(&d->ahci, i);
     }