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

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: <476456e1-ac50-8e48-260d-5cbe5e8b085e@redhat.com>
Date:   Mon, 11 Sep 2023 11:50:31 +0200
From:   David Hildenbrand <david@...hat.com>
To:     "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>
Cc:     Adrian Hunter <adrian.hunter@...el.com>,
        Borislav Petkov <bp@...en8.de>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Dave Hansen <dave.hansen@...el.com>,
        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 11.09.23 11:27, Kirill A. Shutemov wrote:
> On Mon, Sep 11, 2023 at 10:42:51AM +0200, David Hildenbrand wrote:
>> On 11.09.23 10:41, Kirill A. Shutemov wrote:
>>> On Mon, Sep 11, 2023 at 10:03:36AM +0200, David Hildenbrand wrote:
>>>> On 06.09.23 09:39, Adrian Hunter wrote:
>>>>> Support for unaccepted memory was added recently, refer commit
>>>>> dcdfdd40fa82 ("mm: Add support for unaccepted memory"), whereby
>>>>> a virtual machine may need to accept memory before it can be used.
>>>>>
>>>>> Do not map unaccepted memory because it can cause the guest to fail.
>>>>>
>>>>> For /proc/vmcore, which is read-only, this means a read or mmap of
>>>>> unaccepted memory will return zeros.
>>>>
>>>> Does a second (kdump) kernel that exposes /proc/vmcore reliably get access
>>>> to the information whether memory of the first kernel is unaccepted (IOW,
>>>> not its memory, but the memory of the first kernel it is supposed to expose
>>>> via /proc/vmcore)?
>>>
>>> There are few patches in my queue to few related issue, but generally,
>>> yes, the information is available to the target kernel via EFI
>>> configuration table.
>>
>> I assume that table provided by the first kernel, and not read directly from
>> HW, correct?
> 
> The table is constructed by the EFI stub in the first kernel based on EFI
> memory map.
> 

Okay, should work then once that's done by the first kernel.

Maybe include this patch in your series?

-- 
Cheers,

David / dhildenb