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Re: [PATCH-for-6.2 1/2] hw/scsi/lsi53c895a: Do not abort when DMA reques


From: Laurent Vivier
Subject: Re: [PATCH-for-6.2 1/2] hw/scsi/lsi53c895a: Do not abort when DMA requested and no data queued
Date: Tue, 23 Nov 2021 12:26:01 +0100
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.3.0

On 23/11/2021 12:17, Philippe Mathieu-Daudé wrote:
If asked for DMA request and no data is available, simply wait
for data to be queued, do not abort. This fixes:

   $ cat << EOF | \
     qemu-system-i386 -nographic -M q35,accel=qtest -serial none \
       -monitor none -qtest stdio -trace lsi* \
       -drive if=none,id=drive0,file=null-co://,file.read-zeroes=on,format=raw \
       -device lsi53c895a,id=scsi0 -device 
scsi-hd,drive=drive0,bus=scsi0.0,channel=0,scsi-id=0,lun=0
   lsi_reset Reset
   lsi_reg_write Write reg DSP2 0x2e = 0xff
   lsi_reg_write Write reg DSP3 0x2f = 0xff
   lsi_execute_script SCRIPTS dsp=0xffff0000 opcode 0x184a3900 arg 0x4a8b2d75
   qemu-system-i386: hw/scsi/lsi53c895a.c:624: lsi_do_dma: Assertion 
`s->current' failed.

   (gdb) bt
   #5  0x00007ffff4e8a3a6 in __GI___assert_fail
       (assertion=0x5555560accbc "s->current", file=0x5555560acc28 
"hw/scsi/lsi53c895a.c", line=624, function=0x5555560adb18 "lsi_do_dma") at assert.c:101
   #6  0x0000555555aa33b9 in lsi_do_dma (s=0x555557805ac0, out=1) at 
hw/scsi/lsi53c895a.c:624
   #7  0x0000555555aa5042 in lsi_execute_script (s=0x555557805ac0) at 
hw/scsi/lsi53c895a.c:1250
   #8  0x0000555555aa757a in lsi_reg_writeb (s=0x555557805ac0, offset=47, 
val=255 '\377') at hw/scsi/lsi53c895a.c:1984
   #9  0x0000555555aa875b in lsi_mmio_write (opaque=0x555557805ac0, addr=47, 
val=255, size=1) at hw/scsi/lsi53c895a.c:2095

Cc: qemu-stable@nongnu.org
Cc: Gerd Hoffmann <kraxel@redhat.com>
Cc: Vadim Rozenfeld <vrozenfe@redhat.com>
Cc: Stefan Hajnoczi <stefanha@redhat.com>
Reported-by: Jérôme Poulin <jeromepoulin@gmail.com>
Reported-by: Ruhr-University <bugs-syssec@rub.de>
Reported-by: Gaoning Pan <pgn@zju.edu.cn>
Reported-by: Cheolwoo Myung <cwmyung@snu.ac.kr>
Fixes: b96a0da06bd ("lsi: move dma_len+dma_buf into lsi_request")
BugLink: https://bugs.launchpad.net/qemu/+bug/697510
BugLink: https://bugs.launchpad.net/qemu/+bug/1905521
BugLink: https://bugs.launchpad.net/qemu/+bug/1908515
Resolves: https://gitlab.com/qemu-project/qemu/-/issues/84
Resolves: https://gitlab.com/qemu-project/qemu/-/issues/305
Resolves: https://gitlab.com/qemu-project/qemu/-/issues/552
Signed-off-by: Philippe Mathieu-Daudé <philmd@redhat.com>
---
  hw/scsi/lsi53c895a.c | 3 +--
  1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/hw/scsi/lsi53c895a.c b/hw/scsi/lsi53c895a.c
index 85e907a7854..4c431adb774 100644
--- a/hw/scsi/lsi53c895a.c
+++ b/hw/scsi/lsi53c895a.c
@@ -621,8 +621,7 @@ static void lsi_do_dma(LSIState *s, int out)
      dma_addr_t addr;
      SCSIDevice *dev;
- assert(s->current);
-    if (!s->current->dma_len) {
+    if (!s->current || !s->current->dma_len) {
          /* Wait until data is available.  */
          trace_lsi_do_dma_unavailable();
          return;


Reviewed-by: Laurent Vivier <lvivier@redhat.com>




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