Re: [Qemu-devel] [Qemu-ppc] [PATCH for-2.5] mac_dbdma: always initialize channel field in DBDMA_channel

["Hervé Poussineau" <hpoussin@reactos.org>]

Le 13/11/2015 05:09, Programmingkid a écrit :
>
> On Nov 12, 2015, at 11:04 PM, qemu-ppc-request@nongnu.org wrote:
>
>> Message: 3
>> Date: Thu, 12 Nov 2015 22:24:08 +0100
>> From: Herv? Poussineau <hpoussin@reactos.org>
>> To: qemu-devel@nongnu.org
>> Cc: "open list:Old World" <qemu-ppc@nongnu.org>, Herv? Poussineau
>> 	<hpoussin@reactos.org>
>> Subject: [Qemu-ppc] [PATCH for-2.5] mac_dbdma: always initialize
>> 	channel	field in DBDMA_channel
>> Message-ID: <1447363448-20405-1-git-send-email-hpoussin@reactos.org>
>> Content-Type: text/plain; charset=UTF-8
>>
>> dbdma_from_ch() uses channel field to return the right DBDMA object.
>> Previous code was working if guest OS was only using registered DMA channels.
>> However, it lead to QEMU crashes if guest OS was using unregistered DMA channels.
>>
>> Signed-off-by: Herv? Poussineau <hpoussin@reactos.org>
>> ---
>> hw/misc/macio/mac_dbdma.c | 2 +-
>> 1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/hw/misc/macio/mac_dbdma.c b/hw/misc/macio/mac_dbdma.c
>> index 779683c..5ee8f02 100644
>> --- a/hw/misc/macio/mac_dbdma.c
>> +++ b/hw/misc/macio/mac_dbdma.c
>> @@ -557,7 +557,6 @@ void DBDMA_register_channel(void *dbdma, int nchan, qemu_irq irq,
>>      DBDMA_DPRINTF("DBDMA_register_channel 0x%x\n", nchan);
>>
>>      ch->irq = irq;
>> -    ch->channel = nchan;
>>      ch->rw = rw;
>>      ch->flush = flush;
>>      ch->io.opaque = opaque;
>> @@ -753,6 +752,7 @@ void* DBDMA_init (MemoryRegion **dbdma_mem)
>>      for (i = 0; i < DBDMA_CHANNELS; i++) {
>>          DBDMA_io *io = &s->channels[i].io;
>>          qemu_iovec_init(&io->iov, 1);
>> +        s->channels[i].channel = i;
>>      }
>>
>>      memory_region_init_io(&s->mem, NULL, &dbdma_ops, s, "dbdma", 0x1000);
>> --
>> 2.1.4
>
> What operating system(s) did you use to test this patch out?
>

It was during some custom tests with OpenBIOS, where i miswrote the IDE DMA channel.

However, you can see the problem by using this "patch":
diff --git a/hw/ide/macio.c b/hw/ide/macio.c
index 3ee962f..73dfec0 100644
--- a/hw/ide/macio.c
+++ b/hw/ide/macio.c
@@ -629,7 +629,7 @@ void macio_ide_init_drives(MACIOIDEState *s, DriveInfo **hd_table)
  void macio_ide_register_dma(MACIOIDEState *s, void *dbdma, int channel)
  {
      s->dbdma = dbdma;
-    DBDMA_register_channel(dbdma, channel, s->dma_irq,
+    DBDMA_register_channel(dbdma, channel + 1, s->dma_irq,
                             pmac_ide_transfer, pmac_ide_flush, s);
  }

And starting whatever operating system. As soon as DMA is used to read the disk/cdrom, QEMU will crash.

Regards,

Hervé