linux-kernel - Re: [PATCH] mm/early_ioremap: Print the starting physical address in __early

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Message-ID: <aWNqQd3CVx8Z_KFB@kernel.org>
Date: Sun, 11 Jan 2026 11:15:45 +0200
From: Mike Rapoport <rppt@...nel.org>
To: Andrew Morton <akpm@...ux-foundation.org>
Cc: Hou Wenlong <houwenlong.hwl@...group.com>, linux-kernel@...r.kernel.org,
	David Hildenbrand <david@...nel.org>,
	Lorenzo Stoakes <lorenzo.stoakes@...cle.com>,
	"Liam R. Howlett" <Liam.Howlett@...cle.com>,
	Vlastimil Babka <vbabka@...e.cz>,
	Suren Baghdasaryan <surenb@...gle.com>,
	Michal Hocko <mhocko@...e.com>, linux-mm@...ck.org
Subject: Re: [PATCH] mm/early_ioremap: Print the starting physical address in
 __early_ioremap()

On Sat, Jan 10, 2026 at 03:57:21PM -0800, Andrew Morton wrote:
> On Fri,  9 Jan 2026 21:31:51 +0800 Hou Wenlong <houwenlong.hwl@...group.com> wrote:
> 
> > The debug WARN() printing occurs after the while loop, so the
> > 'phys_addr' reflects the last physical address rather than the actual
> > starting physical address, which is not useful for debugging. To
> > simplify, the WARN() statement could be moved up before the loop instead
> > of introducing a new variable to record the original 'phys_addr' value.
> > Additionally, swap the print order of 'slot_virt[slot]' and 'offset', as
> > this will enhance output readability.
> > 
> 
> yep, thanks.
> 
> > --- a/mm/early_ioremap.c
> > +++ b/mm/early_ioremap.c
> > @@ -139,6 +139,9 @@ __early_ioremap(resource_size_t phys_addr, unsigned long size, pgprot_t prot)
> >  	if (WARN_ON(nrpages > NR_FIX_BTMAPS))
> >  		return NULL;
> >  
> > +	WARN(early_ioremap_debug, "%s(%pa, %08lx) [%d] => %08lx + %08lx\n",
> > +	     __func__, &phys_addr, size, slot, slot_virt[slot], offset);
> > +
> >  	/*
> >  	 * Ok, go for it..
> >  	 */
> > @@ -152,8 +155,6 @@ __early_ioremap(resource_size_t phys_addr, unsigned long size, pgprot_t prot)
> >  		--idx;
> >  		--nrpages;
> >  	}
> > -	WARN(early_ioremap_debug, "%s(%pa, %08lx) [%d] => %08lx + %08lx\n",
> > -	     __func__, &phys_addr, size, slot, offset, slot_virt[slot]);
> 
> It's strange that this code uses WARN when nothing is wrong.  The rest
> of the function uses WARN appropriately.  But that's off-topic!

It seems an historic thing. A nice cleanup would be to replace
WARN(early_ioremap_debug) with pr_warn() + dump_stack().
 
> Reviewed-by: Andrew Morton <akpm@...ux-foundation.org>
> 

-- 
Sincerely yours,
Mike.