ahci/qtest: Execute IDENTIFY prior to data commands

If you try to execute an NCQ command before trying to engage with the
device by issuing an IDENTIFY command, the error bits that are part of
the signature will fool the test suite into thinking there was a failure.

Issue IDENTIFY first on "boot", which will clear the signature out of
the registers for us.
Signed-off-by: NJohn Snow <jsnow@redhat.com>
Reviewed-by: NStefan Hajnoczi <stefanha@redhat.com>
Message-id: 1435016308-6150-9-git-send-email-jsnow@redhat.com

tests/ahci-test.c

@@ -228,6 +228,8 @@ static AHCIQState *ahci_boot_and_enable(const char *cli, ...)
 {
     AHCIQState *ahci;
     va_list ap;
+    uint16_t buff[256];
+    uint8_t port;
 
     if (cli) {
         va_start(ap, cli);
@@ -239,6 +241,10 @@ static AHCIQState *ahci_boot_and_enable(const char *cli, ...)
 
     ahci_pci_enable(ahci);
     ahci_hba_enable(ahci);
+    /* Initialize test device */
+    port = ahci_port_select(ahci);
+    ahci_port_clear(ahci, port);
+    ahci_io(ahci, port, CMD_IDENTIFY, &buff, sizeof(buff), 0);
 
     return ahci;
 }