[PATCH v3 09/14] scsi-disk: add SCSI_DISK_QUIRK_MODE_PAGE_TRUNCATED quirk for Macintosh

[Mark Cave-Ayland]

When A/UX configures the CDROM device it sends a truncated MODE SELECT request
for page 1 (MODE_PAGE_R_W_ERROR) which is only 6 bytes in length rather than
10. This seems to be due to bug in Apple's code which calculates the CDB message
length incorrectly.

The work at [1] suggests that this truncated request is accepted on real
hardware whereas in QEMU it generates an INVALID_PARAM_LEN sense code which
causes A/UX to get stuck in a loop retrying the command in an attempt to 
succeed.

Alter the mode page request length check so that truncated requests are allowed
if the SCSI_DISK_QUIRK_MODE_PAGE_TRUNCATED quirk is enabled, whilst also adding 
a
trace event to enable the condition to be detected.

[1] 
https://68kmla.org/bb/index.php?threads/scsi2sd-project-anyone-interested.29040/page-7#post-316444

Signed-off-by: Mark Cave-Ayland <mark.cave-ayland@ilande.co.uk>
---
 hw/scsi/scsi-disk.c    | 7 ++++++-
 hw/scsi/trace-events   | 1 +
 include/hw/scsi/scsi.h | 1 +
 3 files changed, 8 insertions(+), 1 deletion(-)

diff --git a/hw/scsi/scsi-disk.c b/hw/scsi/scsi-disk.c
index f09c1acae2..b225ec1a4c 100644
--- a/hw/scsi/scsi-disk.c
+++ b/hw/scsi/scsi-disk.c
@@ -1552,7 +1552,10 @@ static int mode_select_pages(SCSIDiskReq *r, uint8_t *p, 
int len, bool change)
             goto invalid_param;
         }
         if (page_len > len) {
-            goto invalid_param_len;
+            if (!(s->quirks & SCSI_DISK_QUIRK_MODE_PAGE_TRUNCATED)) {
+                goto invalid_param_len;
+            }
+            trace_scsi_disk_mode_select_page_truncated(page, page_len, len);
         }
 
         if (!change) {
@@ -3152,6 +3155,8 @@ static Property scsi_cd_properties[] = {
     DEFINE_PROP_BIT("quirk_mode_page_vendor_specific_apple", SCSIDiskState,
                     quirks, SCSI_DISK_QUIRK_MODE_PAGE_VENDOR_SPECIFIC_APPLE,
                     0),
+    DEFINE_PROP_BIT("quirk_mode_page_truncated", SCSIDiskState, quirks,
+                    SCSI_DISK_QUIRK_MODE_PAGE_TRUNCATED, 0),
     DEFINE_PROP_END_OF_LIST(),
 };
 
diff --git a/hw/scsi/trace-events b/hw/scsi/trace-events
index 03b2640934..8e927ff62d 100644
--- a/hw/scsi/trace-events
+++ b/hw/scsi/trace-events
@@ -339,6 +339,7 @@ scsi_disk_dma_command_READ(uint64_t lba, uint32_t len) 
"Read (sector %" PRId64 "
 scsi_disk_dma_command_WRITE(const char *cmd, uint64_t lba, int len) "Write 
%s(sector %" PRId64 ", count %u)"
 scsi_disk_new_request(uint32_t lun, uint32_t tag, const char *line) "Command: 
lun=%d tag=0x%x data=%s"
 scsi_disk_aio_sgio_command(uint32_t tag, uint8_t cmd, uint64_t lba, int len, 
uint32_t timeout) "disk aio sgio: tag=0x%x cmd=0x%x (sector %" PRId64 ", count 
%d) timeout=%u"
+scsi_disk_mode_select_page_truncated(int page, int len, int page_len) "page %d 
expected length %d but received length %d"
 
 # scsi-generic.c
 scsi_generic_command_complete_noio(void *req, uint32_t tag, int statuc) 
"Command complete %p tag=0x%x status=%d"
diff --git a/include/hw/scsi/scsi.h b/include/hw/scsi/scsi.h
index 011cb84753..e284e3a4ec 100644
--- a/include/hw/scsi/scsi.h
+++ b/include/hw/scsi/scsi.h
@@ -230,5 +230,6 @@ extern const SCSIReqOps scsi_generic_req_ops;
 #define SCSI_DISK_QUIRK_MODE_PAGE_APPLE_VENDOR             0
 #define SCSI_DISK_QUIRK_MODE_SENSE_ROM_USE_DBD             1
 #define SCSI_DISK_QUIRK_MODE_PAGE_VENDOR_SPECIFIC_APPLE    2
+#define SCSI_DISK_QUIRK_MODE_PAGE_TRUNCATED                3
 
 #endif
-- 
2.30.2