linux-kernel - Re: [PATCH] mm: ignore nomap memory during mirror init

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <aHj8mfecDhJJZW1Y@kernel.org>
Date: Thu, 17 Jul 2025 16:37:29 +0300
From: Mike Rapoport <rppt@...nel.org>
To: mawupeng <mawupeng1@...wei.com>
Cc: akpm@...ux-foundation.org, ardb@...nel.org, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] mm: ignore nomap memory during mirror init

On Thu, Jul 17, 2025 at 07:06:52PM +0800, mawupeng wrote:
> 
> On 2025/7/17 18:29, Mike Rapoport wrote:
> > On Thu, Jul 17, 2025 at 04:57:23PM +0800, Wupeng Ma wrote:
> >> When memory mirroring is enabled, the BIOS may reserve memory regions
> >> at the start of the physical address space without the MR flag. This will
> >> lead to zone_movable_pfn to be updated to the start of these reserved
> >> regions, resulting in subsequent mirrored memory being ignored.
> >>
> >> Here is the log with efi=debug enabled:
> >>   efi:   0x084004000000-0x0842bf37ffff [Conventional|   |  |MR|...|WB|WT|WC|  ]
> >>   efi:   0x0842bf380000-0x0842c21effff [Loader Code |   |  |MR|...|WB|WT|WC|  ]
> >>   efi:   0x0842c21f0000-0x0847ffffffff [Conventional|   |  |MR|...|WB|WT|WC|  ]
> >>   efi:   0x085000000000-0x085fffffffff [Conventional|   |  |  |...|WB|WT|WC|  ]
> >> ...
> >>   efi:   0x084000000000-0x084003ffffff [Reserved    |   |  |  |...|WB|WT|WC|  ]
> >>
> >> Since this kind of memory can not be used by kernel. ignore nomap memory to fix
> >> this issue.
> 
> Since the first non-mirror pfn of this node is 0x084000000000, then zone_movable_pfn 
> for this node will be updated to this. This will lead to Mirror Region 
>   - 0x084004000000-0x0842bf37ffff
>   - 0x0842bf380000-0x0842c21effff 
>   - 0x0842c21f0000-0x0847ffffffff
> be seen as non-mirror memory since zone_movable_pfn will be the start_pfn of this node
> in adjust_zone_range_for_zone_movable().

What do you mean by "seen as non-mirror memory"?

What is the problem with having movable zone on that node start at
0x084000000000?

Can you post the kernel log up to "Memory: nK/mK available" line for more
context?
 
> So igore nomap memory to fix this problem.
> 
> > 
> > If the memory is nomap it won't be used by the kernel anyway.
> > What's the actual issue you are trying to fix?
> >  
> >> Signed-off-by: Wupeng Ma <mawupeng1@...wei.com>
> >> ---
> >>  mm/mm_init.c | 2 +-
> >>  1 file changed, 1 insertion(+), 1 deletion(-)
> >>
> >> diff --git a/mm/mm_init.c b/mm/mm_init.c
> >> index f2944748f526..1c36518f0fe4 100644
> >> --- a/mm/mm_init.c
> >> +++ b/mm/mm_init.c
> >> @@ -405,7 +405,7 @@ static void __init find_zone_movable_pfns_for_nodes(void)
> >>  		}
> >>  
> >>  		for_each_mem_region(r) {
> >> -			if (memblock_is_mirror(r))
> >> +			if (memblock_is_mirror(r) || memblock_is_nomap(r))
> >>  				continue;
> >>  
> >>  			nid = memblock_get_region_node(r);
> >> -- 
> >> 2.43.0
> >>
> > 
> 

-- 
Sincerely yours,
Mike.