From 02a3ce56a7573d4c7b173b570abda9f239666dc0 Mon Sep 17 00:00:00 2001 From: Mark Cave-Ayland Date: Fri, 12 Jan 2024 12:54:04 +0000 Subject: [PATCH] esp.c: handle TC underflow for DMA SCSI requests Detect the case where the guest underflows TC by requesting a DMA transfer which is larger than the available data. If this case is detected, immediately complete the SCSI request and handle any remaining FIFO accesses in the STATUS phase by raising INTR_BS once the FIFO is below the threshold. Note that handling the premature SCSI bus phase change in the case of TC underflow fixes booting EMILE on m68k once again. Signed-off-by: Mark Cave-Ayland Tested-by: Helge Deller Tested-by: Thomas Huth Message-Id: <20240112125420.514425-73-mark.cave-ayland@ilande.co.uk> Signed-off-by: Mark Cave-Ayland --- hw/scsi/esp.c | 25 ++++++++++++++++++++++++- 1 file changed, 24 insertions(+), 1 deletion(-) diff --git a/hw/scsi/esp.c b/hw/scsi/esp.c index 8ea100ee9c..a3e18bb3d7 100644 --- a/hw/scsi/esp.c +++ b/hw/scsi/esp.c @@ -579,6 +579,12 @@ static void esp_do_dma(ESPState *s) s->async_len -= len; s->ti_size -= len; + if (s->async_len == 0 && s->ti_size == 0 && esp_get_tc(s)) { + /* If the guest underflows TC then terminate SCSI request */ + scsi_req_continue(s->current_req); + return; + } + if (s->async_len == 0 && fifo8_num_used(&s->fifo) < 2) { /* Defer until the scsi layer has completed */ scsi_req_continue(s->current_req); @@ -596,6 +602,12 @@ static void esp_do_dma(ESPState *s) esp_set_tc(s, esp_get_tc(s) - len); esp_raise_drq(s); + if (s->async_len == 0 && s->ti_size == 0 && esp_get_tc(s)) { + /* If the guest underflows TC then terminate SCSI request */ + scsi_req_continue(s->current_req); + return; + } + if (s->async_len == 0 && fifo8_num_used(&s->fifo) < 2) { /* Defer until the scsi layer has completed */ scsi_req_continue(s->current_req); @@ -630,6 +642,15 @@ static void esp_do_dma(ESPState *s) } } break; + + default: + /* Consume remaining data if the guest underflows TC */ + if (fifo8_num_used(&s->fifo) < 2) { + s->rregs[ESP_RINTR] |= INTR_BS; + esp_raise_irq(s); + esp_lower_drq(s); + } + break; } break; @@ -884,7 +905,9 @@ void esp_command_complete(SCSIRequest *req, size_t resid) esp_set_phase(s, STAT_ST); s->rregs[ESP_RINTR] |= INTR_BS; esp_raise_irq(s); - esp_lower_drq(s); + + /* Ensure DRQ is set correctly for TC underflow or normal completion */ + esp_dma_ti_check(s); if (s->current_req) { scsi_req_unref(s->current_req);