Re: [Qemu-devel] Provide safe_syscall for s390x

[Aurelien Jarno]

On 2016-10-17 07:35, Richard Henderson wrote:
> On 10/17/2016 03:55 AM, Christian Borntraeger wrote:
> > On 10/17/2016 10:26 AM, Thomas Huth wrote:
> > > On 14.10.2016 20:58, Michael Tokarev wrote:
> > > > Hi.
> > > > 
> > > > This commit: c9bc3437a905b660561a26cd4ecc64579843267b
> > > > Author: Richard Henderson <address@hidden>
> > > > Date:   Tue Jun 21 17:32:12 2016 -0700
> > > > 
> > > >     linux-user: Provide safe_syscall for s390x
> > > > 
> > > > does not build on debian unstable porterbox for s390x, with
> > > > the following error message:
> > > > 
> > > > linux-user/host/s390x/safe-syscall.inc.S: Assembler messages:
> > > > linux-user/host/s390x/safe-syscall.inc.S:75: Error: Unrecognized opcode:
> > > > `lt'
> > > > rules.mak:72: recipe for target 'linux-user/safe-syscall.o' failed
> > > > 
> > > > Since I know nothing about s390, I've no idea what's at fault
> > > > here... :)  Thought I'd report this :)
> > > 
> > > "lt" seems to be a newer s390x opcode which has been added to the
> > > architecture within the last ten years or so. So maybe you've got to add
> > > some "-march=xxx" flag when compiling this file?
> > > Could you maybe start with finding out the exact comand line that is
> > > used to compile this file?
> > 
> > Yes, lt was added with the extended immidiate facility. So either use 
> > -march=z9-109 (introduced in
> > 2005) or replace the lt with an l + ltr to also run on older models.
> > 
> 
> Whoops.  I'd forgotten that RHEL defaults to z196 these days.  This piece of
> code is certainly not important enough to conditionalize on newer hardware.
> I'll put together a patch.

Actually gcc suggests to use icm %r0,15,0(%r8). It's even shorter than
lt %r0,0(%r8).

Aurelien

-- 
Aurelien Jarno                          GPG: 4096R/1DDD8C9B
address@hidden                 http://www.aurel32.net