Re: [Qemu-devel] [PATCH v5 45/76] target/mips: Implement emulation of nanoMIPS LLWP/SCWP pair

[Aleksandar Rikalo]

Hi, Richard,


The nanoMIPS binary that triggers this error is in the attachment.

You can find source code also.


Best Regards,

Aleksandar Rikalo


________________________________
From: Aleksandar Markovic
Sent: Thursday, August 2, 2018 7:54:31 PM
To: Richard Henderson; Aleksandar Markovic; address@hidden; Aleksandar Rikalo
Cc: address@hidden; address@hidden; address@hidden; address@hidden; Stefan 
Markovic; Petar Jovanovic; Paul Burton
Subject: Re: [PATCH v5 45/76] target/mips: Implement emulation of nanoMIPS 
LLWP/SCWP pair

> From: Richard Henderson <address@hidden>
> Sent: Thursday, August 2, 2018 7:28 PM
>
> On 08/02/2018 08:29 AM, Aleksandar Markovic wrote:
> > Hi, Richard,
> >
> > We are going to remove obsoleted helpers, that was just an honest mistake 
> > made in a rush.
> >
> > For unprotected access to gpr, we are going to insert if(reg1 != 0) in two 
> > places.
>
> Be careful that you do not eliminate side effects in the process.  This
> includes things like check_dspr2, and any helper that sets overflow_flag or
> carry_flag.
>
> I cannot see how you will avoid that when adding only two if statements.
>

I was referring just to SCWP handler function. For DSP patches, for v6, we 
worked assiduously to eliminate all unprotected accesses to gpr.

>
> > However, it looks there is a bigger problem now in SCWP. QEMU crashes with 
> > this message:
> >
> > /qemu/tcg/tcg.c:2862: tcg fatal error
> >
> > This happens in user mode only, system mode case runs fine.
> >
> > the problem seems to appear as a consequence of using tcg_gen_brcond_*(().
> >
> > Do you have any idea what are we doing wrong here?
>
> If you send me a binary that triggers this error, I'll look at it.

Will do it tomorrow morning.

Aleksandar

llscwp
Description: llscwp

llscwp.c
Description: llscwp.c