From: Segher Boessenkool <segher@kernel.crashing.org>
To: Michael Ellerman <mpe@ellerman.id.au>
Cc: linuxppc-dev@lists.ozlabs.org,
Alastair D'Silva <alastair@au1.ibm.com>,
linux-kernel@vger.kernel.org
Subject: Re: [RFC PATCH] powerpc: Convert ____flush_dcache_icache_phys() to C
Date: Mon, 2 Sep 2019 06:11:05 -0500 [thread overview]
Message-ID: <20190902111105.GX31406@gate.crashing.org> (raw)
In-Reply-To: <87imqbtqlw.fsf@mpe.ellerman.id.au>
On Mon, Sep 02, 2019 at 11:48:59AM +1000, Michael Ellerman wrote:
> "Alastair D'Silva" <alastair@au1.ibm.com> writes:
> > On Wed, 2019-08-21 at 22:27 +0200, Christophe Leroy wrote:
> >> Can we be 100% sure that GCC won't add any code accessing some
> >> global data or stack while the Data MMU is OFF ?
> >
> > +mpe
> >
> > I'm not sure how we would go about making such a guarantee, but I've
> > tied every variable used to a register and addr is passed in a
> > register, so there is no stack usage, and every call in there only
> > operates on it's operands.
>
> That's not safe, I can believe it happens to work but the compiler
> people will laugh at us if it ever breaks.
Yes. Sorry.
> Let's leave it in asm.
+1
The asm is simpler, more readable, more maintainable, and perhaps more
performant even. Plus the being-laughed-at issue.
Segher
prev parent reply other threads:[~2019-09-02 11:13 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-08-16 15:52 [RFC PATCH] powerpc: Convert ____flush_dcache_icache_phys() to C Christophe Leroy
2019-08-20 4:36 ` Alastair D'Silva
2019-08-21 20:27 ` Christophe Leroy
2019-08-22 0:27 ` Alastair D'Silva
2019-08-22 5:06 ` Christophe Leroy
2019-08-22 5:47 ` Alastair D'Silva
2019-09-02 1:48 ` Michael Ellerman
2019-09-02 11:11 ` Segher Boessenkool [this message]
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