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

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Message-ID: <5a188bb6-add4-0522-069f-18fbd34aff16@intel.com>
Date:   Thu, 7 Sep 2023 08:51:06 -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 9/7/23 08:44, Adrian Hunter wrote:
> On 7/09/23 18:39, Dave Hansen wrote:
>> 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?
> Someone asked for the change to be in arch-independent code... 😉

That doesn't really answer my question.  virtio_mem_init_kdump(), for
instance, is in arch-independent code.