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| author | Mark Cave-Ayland <mark.cave-ayland@ilande.co.uk> | 2025-07-11 21:46:34 +0100 |
|---|---|---|
| committer | Philippe Mathieu-Daudé <philmd@linaro.org> | 2025-07-15 00:25:13 +0200 |
| commit | 28a579a349015a7ed5a57cb4bdcdc5c60ba6b6fc (patch) | |
| tree | bca63941a80210f640c0c0eea7362435c3ba64c3 | |
| parent | 9d6df740ec5e43bd8e4521901aca95f9780e524a (diff) | |
| download | focaccia-qemu-28a579a349015a7ed5a57cb4bdcdc5c60ba6b6fc.tar.gz focaccia-qemu-28a579a349015a7ed5a57cb4bdcdc5c60ba6b6fc.zip | |
esp.c: only call dma_memory_write 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_write 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: <20250711204636.542964-6-mark.cave-ayland@ilande.co.uk> Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>
| -rw-r--r-- | hw/scsi/esp.c | 6 |
1 files changed, 5 insertions, 1 deletions
diff --git a/hw/scsi/esp.c b/hw/scsi/esp.c index ec9fcbeddf..1c7bad8fc0 100644 --- a/hw/scsi/esp.c +++ b/hw/scsi/esp.c @@ -631,7 +631,9 @@ static void esp_do_dma(ESPState *s) switch (s->rregs[ESP_CMD]) { case CMD_TI | CMD_DMA: if (s->dma_memory_write) { - s->dma_memory_write(s->dma_opaque, s->async_buf, len); + if (len) { + s->dma_memory_write(s->dma_opaque, s->async_buf, len); + } } else { /* Copy device data to FIFO */ len = MIN(len, fifo8_num_free(&s->fifo)); @@ -681,6 +683,7 @@ static void esp_do_dma(ESPState *s) buf[0] = s->status; if (s->dma_memory_write) { + /* Length already non-zero */ s->dma_memory_write(s->dma_opaque, buf, len); } else { esp_fifo_push_buf(s, buf, len); @@ -715,6 +718,7 @@ static void esp_do_dma(ESPState *s) buf[0] = 0; if (s->dma_memory_write) { + /* Length already non-zero */ s->dma_memory_write(s->dma_opaque, buf, len); } else { esp_fifo_push_buf(s, buf, len); |