ahci: clean up initial d2h semantics

with write_fis_d2h and signature generation tidied up,
let's adjust the initial d2h semantics to make more sense.

The initial d2h is considered delivered if there is guest
memory to save it to.
Signed-off-by: NJohn Snow <jsnow@redhat.com>
Reviewed-by: NStefan Hajnoczi <stefanha@redhat.com>
Message-id: 1441140641-17631-5-git-send-email-jsnow@redhat.com

hw/ide/ahci.c

@@ -46,7 +46,7 @@ do { \
 static void check_cmd(AHCIState *s, int port);
 static int handle_cmd(AHCIState *s, int port, uint8_t slot);
 static void ahci_reset_port(AHCIState *s, int port);
-static void ahci_write_fis_d2h(AHCIDevice *ad);
+static bool ahci_write_fis_d2h(AHCIDevice *ad);
 static void ahci_init_d2h(AHCIDevice *ad);
 static int ahci_dma_prepare_buf(IDEDMA *dma, int32_t limit);
 static bool ahci_map_clb_address(AHCIDevice *ad);
@@ -295,7 +295,6 @@ static void  ahci_port_write(AHCIState *s, int port, int offset, uint32_t val)
             if ((pr->cmd & PORT_CMD_FIS_ON) &&
                 !s->dev[port].init_d2h_sent) {
                 ahci_init_d2h(&s->dev[port]);
-                s->dev[port].init_d2h_sent = true;
             }
 
             check_cmd(s, port);
@@ -541,14 +540,19 @@ static void ahci_init_d2h(AHCIDevice *ad)
     IDEState *ide_state = &ad->port.ifs[0];
     AHCIPortRegs *pr = &ad->port_regs;
 
-    /* We're emulating receiving the first Reg H2D Fis from the device;
-     * Update the SIG register, but otherwise proceed as normal. */
-    pr->sig = (ide_state->hcyl << 24) |
-        (ide_state->lcyl << 16) |
-        (ide_state->sector << 8) |
-        (ide_state->nsector & 0xFF);
+    if (ad->init_d2h_sent) {
+        return;
+    }
 
-    ahci_write_fis_d2h(ad);
+    if (ahci_write_fis_d2h(ad)) {
+        ad->init_d2h_sent = true;
+        /* We're emulating receiving the first Reg H2D Fis from the device;
+         * Update the SIG register, but otherwise proceed as normal. */
+        pr->sig = (ide_state->hcyl << 24) |
+            (ide_state->lcyl << 16) |
+            (ide_state->sector << 8) |
+            (ide_state->nsector & 0xFF);
+    }
 }
 
 static void ahci_set_signature(AHCIDevice *ad, uint32_t sig)
@@ -750,7 +754,7 @@ static void ahci_write_fis_pio(AHCIDevice *ad, uint16_t len)
     ahci_trigger_irq(ad->hba, ad, PORT_IRQ_PIOS_FIS);
 }
 
-static void ahci_write_fis_d2h(AHCIDevice *ad)
+static bool ahci_write_fis_d2h(AHCIDevice *ad)
 {
     AHCIPortRegs *pr = &ad->port_regs;
     uint8_t *d2h_fis;
@@ -758,7 +762,7 @@ static void ahci_write_fis_d2h(AHCIDevice *ad)
     IDEState *s = &ad->port.ifs[0];
 
     if (!ad->res_fis || !(pr->cmd & PORT_CMD_FIS_RX)) {
-        return;
+        return false;
     }
 
     d2h_fis = &ad->res_fis[RES_FIS_RFIS];
@@ -791,6 +795,7 @@ static void ahci_write_fis_d2h(AHCIDevice *ad)
     }
 
     ahci_trigger_irq(ad->hba, ad, PORT_IRQ_D2H_REG_FIS);
+    return true;
 }
 
 static int prdt_tbl_entry_size(const AHCI_SG *tbl)