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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)
Date: Fri, 18 Jun 2010 21:56:56 +0200	[thread overview]
Message-ID: <20100618195656.GA3821@elte.hu> (raw)
In-Reply-To: <4C1BCDD5.5040805@zytor.com>


* 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

  reply	other threads:[~2010-06-18 19:57 UTC|newest]

Thread overview: 7+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2010-06-18 19:42 [PATCH] x86: OLPC: add support for calling into OpenFirmware (v5) Andres Salomon
2010-06-18 19:49 ` H. Peter Anvin
2010-06-18 19:56   ` Ingo Molnar [this message]
2010-06-18 20:00     ` H. Peter Anvin
2010-06-19  7:43       ` Ingo Molnar
2010-06-18 20:19   ` Andres Salomon
2010-06-18 20:24     ` H. Peter Anvin

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