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 for kexec@lists.infradead.org; Fri, 15 Mar 2013 20:08:28 +0000
Date: Fri, 15 Mar 2013 21:08:20 +0100
From: Simon Horman <horms@verge.net.au>
Subject: Re: [PATCH] kexec/s390: Replace clgfi with cghi
Message-ID: <20130315200817.GG16561@verge.net.au>
References: <20130315134632.1177a239@holzheu>
 <20130315155732.GF16561@verge.net.au>
 <20130315182549.652495c3@holzheu>
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To: Michael Holzheu <holzheu@linux.vnet.ibm.com>
Cc: kexec@lists.infradead.org

On Fri, Mar 15, 2013 at 06:25:49PM +0100, Michael Holzheu wrote:
> Hello Simon,
> 
> From the "Principles of Operations" (the s390 bible):
> 
> The first operand is compared with the second operand, and the result
> is indicated in the condition code.
> 
> For COMPARE LOGICAL IMMEDIATE (CLGFI), the first operand is treated as
> 64 bits, and the second operand is treated as 32 bits with 32 zeros
> appended on the left.
> 
> This instruction works with 32 bit immediate values.
> 
> For COMPARE HALFWORD IMMEDIATE (CGHI), the first operand is treated as
> a 64-bit signed binary integer.
> 
> This instruction works only with 16 bit immediate values.
> 
> See:
> 
> http://pic.dhe.ibm.com/infocenter/ratdevz/v8r0/topic/com.ibm.tpf.toolkit.hlasm.doc/dz9zr006.pdf
> 
> Because I only want to check against zero the two instructions will
> have the same effect in the purgatory code.

Thanks. I have applied the change.

> Michael
> 
> 
> On Fri, 15 Mar 2013 16:57:33 +0100
> Simon Horman <horms@verge.net.au> wrote:
> 
> > On Fri, Mar 15, 2013 at 01:46:32PM +0100, Michael Holzheu wrote:
> > > The clgfi instruction needs at least z9 machine level. To allow
> > > kexec-tools compiled also with z900, this patch replaces clgfi with
> > > the older cghi instruction.
> > 
> > Hi,
> > 
> > could you update the changelog to include a brief description of the
> > difference between the two instructions - I assume they work the same
> > way in the context of this change.
> > 
> > > Signed-off-by: Michael Holzheu <holzheu@linux.vnet.ibm.com>
> > > ---
> > >  purgatory/arch/s390/setup-s390.S |    2 +-
> > >  1 file changed, 1 insertion(+), 1 deletion(-)
> > > 
> > > Index: kexec-tools-2.0.3/purgatory/arch/s390/setup-s390.S
> > > ===================================================================
> > > --- kexec-tools-2.0.3.orig/purgatory/arch/s390/setup-s390.S
> > > +++ kexec-tools-2.0.3/purgatory/arch/s390/setup-s390.S
> > > @@ -16,7 +16,7 @@ purgatory_start:
> > >  	larl	%r15,lstack_end
> > >  	aghi	%r15,-160
> > >  
> > > -	clgfi	%r2,0
> > > +	cghi	%r2,0
> > >  	je	verify_checksums
> > >  
> > >  	brasl	%r14,purgatory
> > > 
> > > 
> > > _______________________________________________
> > > kexec mailing list
> > > kexec@lists.infradead.org
> > > http://lists.infradead.org/mailman/listinfo/kexec
> > > 
> > 
> 

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