hw/scsi/esp-pci: use correct address register for PCI DMA transfers

The current code in esp_pci_dma_memory_rw() sets the DMA address to the value
of the DMA_SPA (Starting Physical Address) register which is incorrect: this
means that for each callback from the SCSI layer the DMA address is set back
to the starting address.

In the case where only a single SCSI callback occurs (currently for transfer
lengths < 128kB) this works fine, however for larger transfers the DMA address
wraps back to the initial starting address, corrupting the buffer holding the
data transferred to the guest.

Fix esp_pci_dma_memory_rw() to use the DMA_WAC (Working Address Counter) for
the DMA address which is correctly incremented across multiple SCSI layer
transfers.

Signed-off-by: Mark Cave-Ayland <mark.cave-ayland@ilande.co.uk>
Reviewed-by: Guenter Roeck <linux@roeck-us.net>
Tested-by: Guenter Roeck <linux@roeck-us.net>
Message-ID: <20240112131529.515642-2-mark.cave-ayland@ilande.co.uk>
Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>
(cherry picked from commit 84a6835)
Signed-off-by: Michael Tokarev <mjt@tls.msk.ru>

hw/scsi/esp-pci.c

@@ -275,7 +275,7 @@ static void esp_pci_dma_memory_rw(PCIESPState *pci, uint8_t *buf, int len,
         qemu_log_mask(LOG_UNIMP, "am53c974: MDL transfer not implemented\n");
     }
 
-    addr = pci->dma_regs[DMA_SPA];
+    addr = pci->dma_regs[DMA_WAC];
     if (pci->dma_regs[DMA_WBC] < len) {
         len = pci->dma_regs[DMA_WBC];
     }