Re: [PATCH v2 18/42] esp: accumulate SCSI commands for PDMA transfers in cmdbuf instead of pdma_buf

[Mark Cave-Ayland]

On 02/03/2021 17:02, Laurent Vivier wrote:

Le 09/02/2021 à 20:29, Mark Cave-Ayland a écrit :
ESP SCSI commands are already accumulated in cmdbuf and so there is no need to
keep a separate pdma_buf buffer. Accumulate SCSI commands for PDMA transfers in
cmdbuf instead of pdma_buf so update cmdlen accordingly and change pdma_origin
for PDMA transfers to CMD which allows the PDMA origin to be removed.
This commit also removes a stray memcpy() from get_cmd() which is a no-op 
because
cmdlen is always zero at the start of a command.

Notionally the removal of pdma_buf from vmstate_esp_pdma also breaks migration
compatibility for the PDMA subsection until its complete removal by the end of
the series.

Signed-off-by: Mark Cave-Ayland <mark.cave-ayl...@ilande.co.uk>
---
  hw/scsi/esp.c         | 56 +++++++++++++++++++------------------------
  include/hw/scsi/esp.h |  2 --
  2 files changed, 25 insertions(+), 33 deletions(-)

diff --git a/hw/scsi/esp.c b/hw/scsi/esp.c
index 7134c0aff4..b846f022fb 100644
--- a/hw/scsi/esp.c
+++ b/hw/scsi/esp.c
@@ -139,8 +139,6 @@ static void set_pdma(ESPState *s, enum pdma_origin_id 
origin,
  static uint8_t *get_pdma_buf(ESPState *s)
  {
      switch (s->pdma_origin) {
-    case PDMA:
-        return s->pdma_buf;
      case TI:
          return s->ti_buf;
      case CMD:
@@ -161,14 +159,12 @@ static uint8_t esp_pdma_read(ESPState *s)
      }
  
      switch (s->pdma_origin) {
-    case PDMA:
-        val = s->pdma_buf[s->pdma_cur++];
-        break;
      case TI:
          val = s->ti_buf[s->pdma_cur++];
          break;
      case CMD:
-        val = s->cmdbuf[s->pdma_cur++];
+        val = s->cmdbuf[s->cmdlen++];
+        s->pdma_cur++;
          break;
      case ASYNC:
          val = s->async_buf[s->pdma_cur++];
@@ -193,14 +189,12 @@ static void esp_pdma_write(ESPState *s, uint8_t val)
      }
  
      switch (s->pdma_origin) {
-    case PDMA:
-        s->pdma_buf[s->pdma_cur++] = val;
-        break;
      case TI:
          s->ti_buf[s->pdma_cur++] = val;
          break;
      case CMD:
-        s->cmdbuf[s->pdma_cur++] = val;
+        s->cmdbuf[s->cmdlen++] = val;
+        s->pdma_cur++;
          break;
      case ASYNC:
          s->async_buf[s->pdma_cur++] = val;
@@ -256,8 +250,7 @@ static uint32_t get_cmd(ESPState *s, uint8_t *buf, uint8_t 
buflen)
          if (s->dma_memory_read) {
              s->dma_memory_read(s->dma_opaque, buf, dmalen);
          } else {
-            memcpy(s->pdma_buf, buf, dmalen);
-            set_pdma(s, PDMA, 0, dmalen);
+            set_pdma(s, CMD, 0, dmalen);
              esp_raise_drq(s);
              return 0;
          }
@@ -316,24 +309,24 @@ static void satn_pdma_cb(ESPState *s)
      if (get_cmd_cb(s) < 0) {
          return;
      }
-    if (s->pdma_cur != s->pdma_start) {
-        do_cmd(s, get_pdma_buf(s) + s->pdma_start);
+    s->do_cmd = 0;
+    if (s->cmdlen) {
+        do_cmd(s, s->cmdbuf);

I don't understant how you can remove the pdma_start: normally it is here to 
keep track of the
position in the pDMA if the migration is occuraing while a pDMA transfer.

Hi Laurent,

I was going to follow up on your reviews later this evening, however this one caught 
my eye: as per the cover letter, this patchset is a migration break for the q800 
machine. As there are likely more incompatible changes for the q800 machine coming up 
soon, it didn't seem worth the effort (and indeed I don't think it's possible to 
recreate the new internal state with 100% accuracy from the old state).

Migration for ESP devices that don't use PDMA is still supported, and I've tested 
this during development with qemu-system-sparc.


ATB,

Mark.