When writing to the device make sure that the fifo is not empty, otherwise the
fifo will underflow triggering an assert.
Buglink: https://bugs.launchpad.net/qemu/+bug/1909247
Signed-off-by: Mark Cave-Ayland <mark.cave-ayland@ilande.co.uk>
---
hw/scsi/esp.c | 28 ++++++++++++++++------------
1 file changed, 16 insertions(+), 12 deletions(-)
diff --git a/hw/scsi/esp.c b/hw/scsi/esp.c
index ae362c9dfb..bb57125035 100644
--- a/hw/scsi/esp.c
+++ b/hw/scsi/esp.c
@@ -509,18 +509,20 @@ static void do_dma_pdma_cb(ESPState *s)
/* Copy FIFO data to device */
len = MIN(s->async_len, ESP_FIFO_SZ);
len = MIN(len, fifo8_num_used(&s->fifo));
- memcpy(s->async_buf, fifo8_pop_buf(&s->fifo, len, &n), len);
- s->async_buf += n;
- s->async_len -= n;
- s->ti_size += n;
-
- if (n < len) {
- /* Unaligned accesses can cause FIFO wraparound */
- len = len - n;
+ if (len) {
memcpy(s->async_buf, fifo8_pop_buf(&s->fifo, len, &n), len);
s->async_buf += n;
s->async_len -= n;
s->ti_size += n;
+
+ if (n < len) {
+ /* Unaligned accesses can cause FIFO wraparound */
+ len = len - n;
+ memcpy(s->async_buf, fifo8_pop_buf(&s->fifo, len, &n), len);
+ s->async_buf += n;
+ s->async_len -= n;
+ s->ti_size += n;
+ }
}
if (s->async_len == 0) {
@@ -730,10 +732,12 @@ static void esp_do_nodma(ESPState *s)
if (to_device) {
len = MIN(fifo8_num_used(&s->fifo), ESP_FIFO_SZ);
- memcpy(s->async_buf, fifo8_pop_buf(&s->fifo, len, &n), len);
- s->async_buf += len;
- s->async_len -= len;
- s->ti_size += len;
+ if (len) {
+ memcpy(s->async_buf, fifo8_pop_buf(&s->fifo, len, &n), len);
+ s->async_buf += len;
+ s->async_len -= len;
+ s->ti_size += len;
+ }
} else {
len = MIN(s->ti_size, s->async_len);
len = MIN(len, fifo8_num_free(&s->fifo));
--
2.20.1