linux-kernel - Re: [PATCH v2 5/8] riscv: mm: Take memory hotplug read-lock during kernel page table dump

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Date: Tue, 14 May 2024 22:39:30 +0200
From: David Hildenbrand <david@...hat.com>
To: Björn Töpel <bjorn@...nel.org>,
 Alexandre Ghiti <alexghiti@...osinc.com>, Albert Ou <aou@...s.berkeley.edu>,
 Palmer Dabbelt <palmer@...belt.com>, Paul Walmsley
 <paul.walmsley@...ive.com>, linux-riscv@...ts.infradead.org
Cc: Björn Töpel <bjorn@...osinc.com>,
 Andrew Bresticker <abrestic@...osinc.com>,
 Chethan Seshadri <Chethan.Seshadri@...alinasystems.io>,
 Lorenzo Stoakes <lstoakes@...il.com>, Oscar Salvador <osalvador@...e.de>,
 Santosh Mamila <santosh.mamila@...alinasystems.io>,
 Sivakumar Munnangi <siva.munnangi@...alinasystems.io>,
 Sunil V L <sunilvl@...tanamicro.com>, linux-kernel@...r.kernel.org,
 linux-mm@...ck.org, virtualization@...ts.linux-foundation.org
Subject: Re: [PATCH v2 5/8] riscv: mm: Take memory hotplug read-lock during
 kernel page table dump

On 14.05.24 16:04, Björn Töpel wrote:
> From: Björn Töpel <bjorn@...osinc.com>
> 
> During memory hot remove, the ptdump functionality can end up touching
> stale data. Avoid any potential crashes (or worse), by holding the
> memory hotplug read-lock while traversing the page table.
> 
> This change is analogous to arm64's commit bf2b59f60ee1 ("arm64/mm:
> Hold memory hotplug lock while walking for kernel page table dump").
> 
> Signed-off-by: Björn Töpel <bjorn@...osinc.com>
> ---
>   arch/riscv/mm/ptdump.c | 3 +++
>   1 file changed, 3 insertions(+)
> 
> diff --git a/arch/riscv/mm/ptdump.c b/arch/riscv/mm/ptdump.c
> index 1289cc6d3700..9d5f657a251b 100644
> --- a/arch/riscv/mm/ptdump.c
> +++ b/arch/riscv/mm/ptdump.c
> @@ -6,6 +6,7 @@
>   #include <linux/efi.h>
>   #include <linux/init.h>
>   #include <linux/debugfs.h>
> +#include <linux/memory_hotplug.h>
>   #include <linux/seq_file.h>
>   #include <linux/ptdump.h>
>   
> @@ -370,7 +371,9 @@ bool ptdump_check_wx(void)
>   
>   static int ptdump_show(struct seq_file *m, void *v)
>   {
> +	get_online_mems();
>   	ptdump_walk(m, m->private);
> +	put_online_mems();
>   
>   	return 0;
>   }

Reviewed-by: David Hildenbrand <david@...hat.com>

-- 
Cheers,

David / dhildenb