If no bytes are there to process in the message in phase, the input data latch (s->sidl) is set to s->msg[-1]. Just do nothing since no DMA is performed.
Reported-by: Chuhong Yuan <hsleste...@gmail.com> Reviewed-by: Philippe Mathieu-Daudé <phi...@linaro.org> Signed-off-by: Paolo Bonzini <pbonz...@redhat.com> --- hw/scsi/lsi53c895a.c | 19 ++++++++++++------- 1 file changed, 12 insertions(+), 7 deletions(-) diff --git a/hw/scsi/lsi53c895a.c b/hw/scsi/lsi53c895a.c index 71f759a59dd..eb9828dd5ef 100644 --- a/hw/scsi/lsi53c895a.c +++ b/hw/scsi/lsi53c895a.c @@ -927,13 +927,18 @@ static void lsi_do_msgin(LSIState *s) assert(len > 0 && len <= LSI_MAX_MSGIN_LEN); if (len > s->dbc) len = s->dbc; - pci_dma_write(PCI_DEVICE(s), s->dnad, s->msg, len); - /* Linux drivers rely on the last byte being in the SIDL. */ - s->sidl = s->msg[len - 1]; - s->msg_len -= len; - if (s->msg_len) { - memmove(s->msg, s->msg + len, s->msg_len); - } else { + + if (len) { + pci_dma_write(PCI_DEVICE(s), s->dnad, s->msg, len); + /* Linux drivers rely on the last byte being in the SIDL. */ + s->sidl = s->msg[len - 1]; + s->msg_len -= len; + if (s->msg_len) { + memmove(s->msg, s->msg + len, s->msg_len); + } + } + + if (!s->msg_len) { /* ??? Check if ATN (not yet implemented) is asserted and maybe switch to PHASE_MO. */ switch (s->msg_action) { -- 2.44.0