linux-kernel - RE: [PATCH 2/3] arm64: mmu: early_pgtable

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Message-ID: <DB7PR04MB4490B00D34CCC1E3BC475B8888660@DB7PR04MB4490.eurprd04.prod.outlook.com>
Date:   Wed, 13 Feb 2019 11:50:18 +0000
From:   Peng Fan <peng.fan@....com>
To:     Mark Rutland <mark.rutland@....com>
CC:     "catalin.marinas@....com" <catalin.marinas@....com>,
        "will.deacon@....com" <will.deacon@....com>,
        "ard.biesheuvel@...aro.org" <ard.biesheuvel@...aro.org>,
        "yaojun8558363@...il.com" <yaojun8558363@...il.com>,
        "cpandya@...eaurora.org" <cpandya@...eaurora.org>,
        "robin.murphy@....com" <robin.murphy@....com>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "van.freenix@...il.com" <van.freenix@...il.com>
Subject: RE: [PATCH 2/3] arm64: mmu: early_pgtable_alloc: remove unnecessary
 comments

Hi Mark,

> -----Original Message-----
> From: Mark Rutland [mailto:mark.rutland@....com]
> Sent: 2019年2月13日 19:22
> To: Peng Fan <peng.fan@....com>
> Cc: catalin.marinas@....com; will.deacon@....com;
> ard.biesheuvel@...aro.org; yaojun8558363@...il.com;
> cpandya@...eaurora.org; robin.murphy@....com;
> linux-arm-kernel@...ts.infradead.org; linux-kernel@...r.kernel.org;
> van.freenix@...il.com
> Subject: Re: [PATCH 2/3] arm64: mmu: early_pgtable_alloc: remove
> unnecessary comments
> 
> On Wed, Feb 13, 2019 at 09:37:29AM +0000, Peng Fan wrote:
> > The empty zero page has been moved to bss area by commit 5227cfa71f9e
> > ("arm64: mm: place empty_zero_page in bss"),
> > and it alreay added "dsb     ishst" in head.S to make sure the empty
> > zero page visible to PTW.
> >
> > There is no code to reflect the comment, so remove it.
> 
> The comment below refers to the memory pointed to by ptr, which is zeroed
> by the memset. The comment does not refer to the generic
> empty_zero_page.
> 
> This comment is correct, and should stay. Please drop this patch.

I understand wrong. You are right.

Thanks,
Peng.

> 
> Thanks,
> Mark.
> 
> >
> > Signed-off-by: Peng Fan <peng.fan@....com>
> > ---
> >  arch/arm64/mm/mmu.c | 4 ----
> >  1 file changed, 4 deletions(-)
> >
> > diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c index
> > 065202da3ad2..f61fa7c8fd2e 100644
> > --- a/arch/arm64/mm/mmu.c
> > +++ b/arch/arm64/mm/mmu.c
> > @@ -113,10 +113,6 @@ static phys_addr_t __init
> > early_pgtable_alloc(void)
> >
> >  	memset(ptr, 0, PAGE_SIZE);
> >
> > -	/*
> > -	 * Implicit barriers also ensure the zeroed page is visible to the page
> > -	 * table walker
> > -	 */
> >  	pte_clear_fixmap();
> >
> >  	return phys;
> > --
> > 2.16.4
> >