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

From: Dave Hansen <dave.hansen@intel.com>
To: Adrian Hunter <adrian.hunter@intel.com>,
	"Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>,
	Borislav Petkov <bp@alien8.de>,
	Andrew Morton <akpm@linux-foundation.org>
Cc: Vlastimil Babka <vbabka@suse.cz>,
	Mike Rapoport <rppt@linux.ibm.com>,
	Lorenzo Stoakes <lstoakes@gmail.com>,
	Tom Lendacky <thomas.lendacky@amd.com>,
	Baoquan He <bhe@redhat.com>, Vivek Goyal <vgoyal@redhat.com>,
	Dave Young <dyoung@redhat.com>,
	linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org,
	linux-mm@kvack.org, linux-coco@lists.linux.dev,
	linux-efi@vger.kernel.org, kexec@lists.infradead.org
Subject: Re: [PATCH 1/3] proc/vmcore: Do not map unaccepted memory
Date: Thu, 7 Sep 2023 08:51:06 -0700	[thread overview]
Message-ID: <5a188bb6-add4-0522-069f-18fbd34aff16@intel.com> (raw)
In-Reply-To: <30d0cebb-13f9-572e-9baa-b7450fec9108@intel.com>

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.