linux-kernel - Re: [PATCH 1/3] proc/vmcore: Do not map unaccepted memory

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Message-ID: <21bf2e44-3316-2372-44cb-1488f88650f5@intel.com>
Date:   Thu, 7 Sep 2023 08:39:13 -0700
From:   Dave Hansen <dave.hansen@...el.com>
To:     Adrian Hunter <adrian.hunter@...el.com>,
        "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
        Borislav Petkov <bp@...en8.de>,
        Andrew Morton <akpm@...ux-foundation.org>
Cc:     Vlastimil Babka <vbabka@...e.cz>,
        Mike Rapoport <rppt@...ux.ibm.com>,
        Lorenzo Stoakes <lstoakes@...il.com>,
        Tom Lendacky <thomas.lendacky@....com>,
        Baoquan He <bhe@...hat.com>, Vivek Goyal <vgoyal@...hat.com>,
        Dave Young <dyoung@...hat.com>, linux-kernel@...r.kernel.org,
        linux-fsdevel@...r.kernel.org, linux-mm@...ck.org,
        linux-coco@...ts.linux.dev, linux-efi@...r.kernel.org,
        kexec@...ts.infradead.org
Subject: Re: [PATCH 1/3] proc/vmcore: Do not map unaccepted memory

On 9/6/23 00:39, Adrian Hunter wrote:
> @@ -559,7 +567,8 @@ static int vmcore_remap_oldmem_pfn(struct vm_area_struct *vma,
>  	 * pages without a reason.
>  	 */
>  	idx = srcu_read_lock(&vmcore_cb_srcu);
> -	if (!list_empty(&vmcore_cb_list))
> +	if (!list_empty(&vmcore_cb_list) ||
> +	    range_contains_unaccepted_memory(paddr, paddr + size))
>  		ret = remap_oldmem_pfn_checked(vma, from, pfn, size, prot);
>  	else
>  		ret = remap_oldmem_pfn_range(vma, from, pfn, size, prot);

The whole callback mechanism which fs/proc/vmcore.c::pfn_is_ram()
implements seems to be in place to ensure that there aren't a billion
different "ram" checks in here.

Is there a reason you can't register_vmcore_cb() a callback to check for
unaccepted memory?