linux-kernel - Re: [PATCH V3 1/5] powerpc, perf: Add new BHRB related instructions for POWER8

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <14063.1366599003@ale.ozlabs.ibm.com>
Date:	Mon, 22 Apr 2013 12:50:03 +1000
From:	Michael Neuling <mikey@...ling.org>
To:	Michael Ellerman <michael@...erman.id.au>
cc:	Anshuman Khandual <khandual@...ux.vnet.ibm.com>,
	linuxppc-dev@...abs.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH V3 1/5] powerpc, perf: Add new BHRB related instructions for POWER8

Michael Ellerman <michael@...erman.id.au> wrote:

> On Mon, Apr 22, 2013 at 11:13:43AM +1000, Michael Neuling wrote:
> > Michael Ellerman <michael@...erman.id.au> wrote:
> > 
> > > On Thu, Apr 18, 2013 at 05:56:12PM +0530, Anshuman Khandual wrote:
> > > > This patch adds new POWER8 instruction encoding for reading
> > > > the BHRB buffer entries and also clearing it. Encoding for
> > > > "clrbhrb" instruction is straight forward.
> > > 
> > > Which is "clear branch history rolling buffer" ?
> > > 
> > > > But "mfbhrbe"
> > > > encoding involves reading a certain index of BHRB buffer
> > > > into a particular GPR register.
> > > 
> > > And "Move from branch history rolling buffer entry" ?
> > > 
> > > > diff --git a/arch/powerpc/include/asm/ppc-opcode.h b/arch/powerpc/include/asm/ppc-opcode.h
> > > > index 8752bc8..93ae5a1 100644
> > > > --- a/arch/powerpc/include/asm/ppc-opcode.h
> > > > +++ b/arch/powerpc/include/asm/ppc-opcode.h
> > > > @@ -82,6 +82,7 @@
> > > >  #define	__REGA0_R31	31
> > > >  
> > > >  /* sorted alphabetically */
> > > > +#define PPC_INST_BHRBE			0x7c00025c
> > > 
> > > I don't think you really need this, just use the literal value below.
> > 
> > The rest of the defines in this file do this, so Anshuman's right. 
> 
> I don't see the point, but sure let's be consistent. Though in that case
> he should do the same for PPC_CLRBHRB below.

Agreed.

Mikey

> 
> > > > @@ -297,6 +298,12 @@
> > > >  #define PPC_NAP			stringify_in_c(.long PPC_INST_NAP)
> > > >  #define PPC_SLEEP		stringify_in_c(.long PPC_INST_SLEEP)
> > > >  
> > > > +/* BHRB instructions */
> > > > +#define PPC_CLRBHRB		stringify_in_c(.long 0x7c00035c)
> > > > +#define PPC_MFBHRBE(r, n)	stringify_in_c(.long PPC_INST_BHRBE | \
> > > > +						__PPC_RS(r) | \
> > > > +							(((n) & 0x1f) << 11))
> > > 
> > > Why are you not using ___PPC_RB(n) here ?
> > 
> > Actually, this is wrong.  The number field should be 10 bits (0x3ff),
> > not 5 (0x1f)  Anshuman please fix.
> 
> ACK.
> 
> cheers
> 
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/