diff options
| author | Mark Cave-Ayland <mark.cave-ayland@ilande.co.uk> | 2025-07-11 21:46:33 +0100 |
|---|---|---|
| committer | Philippe Mathieu-Daudé <philmd@linaro.org> | 2025-07-15 00:25:10 +0200 |
| commit | 9d6df740ec5e43bd8e4521901aca95f9780e524a (patch) | |
| tree | 50489316ac8341eaec2c944d754c28080dbf530b | |
| parent | e70aa5dc299c49c59bd91c80e771db56996c2188 (diff) | |
| download | qemu-9d6df740ec5e43bd8e4521901aca95f9780e524a.zip qemu-9d6df740ec5e43bd8e4521901aca95f9780e524a.tar.gz qemu-9d6df740ec5e43bd8e4521901aca95f9780e524a.tar.bz2 | |
esp.c: only call dma_memory_read function if transfer length is non-zero
In the cases where mixed DMA/non-DMA transfers are used or no data is
available, it is possible for the calculated transfer length to be zero.
Only call the dma_memory_read function where the transfer length is
non-zero to avoid invoking the DMA engine for a zero length transfer
which can have side-effects (along with generating additional tracing
noise).
Signed-off-by: Mark Cave-Ayland <mark.cave-ayland@ilande.co.uk>
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Tested-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Message-ID: <20250711204636.542964-5-mark.cave-ayland@ilande.co.uk>
Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>
| -rw-r--r-- | hw/scsi/esp.c | 20 |
1 files changed, 13 insertions, 7 deletions
diff --git a/hw/scsi/esp.c b/hw/scsi/esp.c index 62ba406..ec9fcbe 100644 --- a/hw/scsi/esp.c +++ b/hw/scsi/esp.c @@ -487,8 +487,10 @@ static void esp_do_dma(ESPState *s) case STAT_MO: if (s->dma_memory_read) { len = MIN(len, fifo8_num_free(&s->cmdfifo)); - s->dma_memory_read(s->dma_opaque, buf, len); - esp_set_tc(s, esp_get_tc(s) - len); + if (len) { + s->dma_memory_read(s->dma_opaque, buf, len); + esp_set_tc(s, esp_get_tc(s) - len); + } } else { len = esp_fifo_pop_buf(s, buf, fifo8_num_used(&s->fifo)); len = MIN(fifo8_num_free(&s->cmdfifo), len); @@ -541,9 +543,11 @@ static void esp_do_dma(ESPState *s) trace_esp_do_dma(cmdlen, len); if (s->dma_memory_read) { len = MIN(len, fifo8_num_free(&s->cmdfifo)); - s->dma_memory_read(s->dma_opaque, buf, len); - fifo8_push_all(&s->cmdfifo, buf, len); - esp_set_tc(s, esp_get_tc(s) - len); + if (len) { + s->dma_memory_read(s->dma_opaque, buf, len); + fifo8_push_all(&s->cmdfifo, buf, len); + esp_set_tc(s, esp_get_tc(s) - len); + } } else { len = esp_fifo_pop_buf(s, buf, fifo8_num_used(&s->fifo)); len = MIN(fifo8_num_free(&s->cmdfifo), len); @@ -572,8 +576,10 @@ static void esp_do_dma(ESPState *s) switch (s->rregs[ESP_CMD]) { case CMD_TI | CMD_DMA: if (s->dma_memory_read) { - s->dma_memory_read(s->dma_opaque, s->async_buf, len); - esp_set_tc(s, esp_get_tc(s) - len); + if (len) { + s->dma_memory_read(s->dma_opaque, s->async_buf, len); + esp_set_tc(s, esp_get_tc(s) - len); + } } else { /* Copy FIFO data to device */ len = MIN(s->async_len, ESP_FIFO_SZ); |