Date: Fri, 18 Jun 2010 21:56:56 +0200
From: Ingo Molnar <mingo@elte.hu>
To: "H. Peter Anvin" <hpa@zytor.com>
Cc: Andres Salomon <dilinger@queued.net>,
       Andrew Morton <akpm@linux-foundation.org>, linux-kernel@vger.kernel.org,
       tglx@linutronix.de, mingo@redhat.com, x86@kernel.org,
       Mitch Bradley <wmb@laptop.org>
Subject: Re: [PATCH] x86: OLPC: add support for calling into OpenFirmware (v5)
Message-ID: <20100618195656.GA3821@elte.hu>
References: <20100618154245.2e00af2a@dev.queued.net>
 <4C1BCDD5.5040805@zytor.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <4C1BCDD5.5040805@zytor.com>
User-Agent: Mutt/1.5.20 (2009-08-17)
Sender: linux-kernel-owner@vger.kernel.org
Content-Length: 985
Lines: 28


* H. Peter Anvin <hpa@zytor.com> wrote:

> On 06/18/2010 12:42 PM, Andres Salomon wrote:
> > +
> > +	/* install OFW's PDE permanently into the kernel's pgtable */
> > +	set_pgd(&swapper_pg_dir[OLPC_OFW_PDE_NR], *ofw_pde);
> > +	flush_tlb();
> > +	early_iounmap(base, sizeof(olpc_ofw_pgd) * PTRS_PER_PGD);
> 
> I just realized... this flush_tlb() is actually not necessary since on x86 
> it is always legal to go from a less permissive configuration to a more 
> permissive, and the initial configuration is "not present" which is 
> maximally nonpermissive.
> 
> Could you take it out and make sure it still works?

small nit: an optimization barrier would still be needed if the result is 
being relied on by the kernel.

Thanks,

	Ingo
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/