linux-kernel - Re: [PATCH] memblock: add no-map alloc functions

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Date: Wed, 17 Apr 2024 08:54:43 +0300
From: Mike Rapoport <rppt@...nel.org>
To: Wei Yang <richard.weiyang@...il.com>
Cc: skseofh@...il.com, robh@...nel.org, saravanak@...gle.com,
	akpm@...ux-foundation.org, devicetree@...r.kernel.org,
	linux-kernel@...r.kernel.org, linux-mm@...ck.org,
	Daero Lee <daero_le.lee@...sung.com>
Subject: Re: [PATCH] memblock: add no-map alloc functions

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.