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Date: Fri, 12 Sep 2008 12:58:39 -0500
From: Anthony Liguori <anthony@codemonkey.ws>
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Subject: Re: [Qemu-devel] LSI SCSI: raise UDC on infinite loop (resend #1)
References: <20080912123831.GA22472@dmt.cnet>
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To: qemu-devel@nongnu.org
Cc: Paul Brook <paul@codesourcery.com>

Paul: do you have an objection to me applying this?

Regards,

Anthony Liguori

Marcelo Tosatti wrote:
> Raise UDC (Unexpected Disconnect) when a large enough number of
> instructions has been executed by the SCRIPTS processor. This "solution"
> is much simpler than temporarily interrupting execution.
>
> This remedies the situation with Windows which downloads SCRIPTS code
> that busy loops on guest main memory. Their drivers _do_ handle UDC 
> appropriately (at least XP and 2003).
>
> It would be nicer to actually detect infinite loops, but until then,
> this bandaid seems acceptable.
>
> Since the situation seems to be rare enough, raise the number 
> of instructions to 10000 (previously 1000).
>
> Three people other than myself had success with this patch.
>
>
> diff --git a/qemu/hw/lsi53c895a.c b/qemu/hw/lsi53c895a.c
> index 72ed5c3..50f66aa 100644
> --- a/qemu/hw/lsi53c895a.c
> +++ b/qemu/hw/lsi53c895a.c
> @@ -840,9 +840,11 @@ static void lsi_execute_script(LSIState *s)
>      uint32_t insn;
>      uint32_t addr;
>      int opcode;
> +    int insn_processed = 0;
>  
>      s->istat1 |= LSI_ISTAT1_SRUN;
>  again:
> +    insn_processed++;
>      insn = read_dword(s, s->dsp);
>      addr = read_dword(s, s->dsp + 4);
>      DPRINTF("SCRIPTS dsp=%08x opcode %08x arg %08x\n", s->dsp, insn, addr);
> @@ -1197,8 +1199,12 @@ again:
>              }
>          }
>      }
> -    /* ??? Need to avoid infinite loops.  */
> -    if (s->istat1 & LSI_ISTAT1_SRUN && !s->waiting) {
> +    if (insn_processed > 10000 && !s->waiting) {
> +        if (!(s->sien0 & LSI_SIST0_UDC))
> +            fprintf(stderr, "inf. loop with UDC masked\n");
> +        lsi_script_scsi_interrupt(s, LSI_SIST0_UDC, 0);
> +        lsi_disconnect(s);
> +    } else if (s->istat1 & LSI_ISTAT1_SRUN && !s->waiting) {
>          if (s->dcntl & LSI_DCNTL_SSM) {
>              lsi_script_dma_interrupt(s, LSI_DSTAT_SSI);
>          } else {
>
>
>