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Date: Wed, 17 Apr 2024 08:54:43 +0300
From: Mike Rapoport <rppt@kernel.org>
To: Wei Yang <richard.weiyang@gmail.com>
Cc: skseofh@gmail.com, robh@kernel.org, saravanak@google.com,
	akpm@linux-foundation.org, devicetree@vger.kernel.org,
	linux-kernel@vger.kernel.org, linux-mm@kvack.org,
	Daero Lee <daero_le.lee@samsung.com>
Subject: Re: [PATCH] memblock: add no-map alloc functions
Message-ID: <Zh9kI81ctisgukT8@kernel.org>
References: <20240415142448.333271-1-skseofh@gmail.com>
 <Zh1HP8IWWjexAUKN@kernel.org>
 <20240417023147.ybefdy6fn5drvq5w@master>
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In-Reply-To: <20240417023147.ybefdy6fn5drvq5w@master>

On Wed, Apr 17, 2024 at 02:31:47AM +0000, Wei Yang wrote:
> On Mon, Apr 15, 2024 at 06:26:55PM +0300, Mike Rapoport wrote:
> [...]
> >> +	
> >
> >This changes behaviour of internal function, what effect will it have on
> >the users?
> >
> >>  	if (!base)
> >>  		return -ENOMEM;
> >>  
> >>  	*res_base = base;
> >>  	if (nomap) {
> >>  		err = memblock_mark_nomap(base, size);
> 
> Mike
> 
> One question may not directly relevant to this thread.
> 
> NOMAP doesn't apply to all arch? I took a look into the direct mapping
> function on x86, memory_map_top_down(). It seems iterate all available pfn
> instead of skipping NOMAP range. 

Right, x86 does not use NOMAP.
NOMAP was introduced to ensure that device/firmware memory on arm64 does
not have an alias mapping in the direct map because MMU does not allow
alias mapping with different caching modes.
 
> >> -		if (err)
> >> -			memblock_phys_free(base, size);
> >>  	}
> >>  
> >>  	kmemleak_ignore_phys(base);
> >
> >-- 
> >Sincerely yours,
> >Mike.
> 
> -- 
> Wei Yang
> Help you, Help me

-- 
Sincerely yours,
Mike.