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Message-ID: <ea1bc666-69ca-9ae4-36cf-cb3d852a0558@redhat.com>
Date:   Tue, 12 Sep 2023 09:50:18 +0200
From:   David Hildenbrand <david@...hat.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>,
        Ard Biesheuvel <ardb@...nel.org>
Cc:     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 V2 1/2] efi/unaccepted: Do not let /proc/vmcore try to
 access unaccepted memory

On 12.09.23 09:47, Adrian Hunter wrote:
> On 12/09/23 10:19, David Hildenbrand wrote:
>> On 11.09.23 13:21, 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 let /proc/vmcore try to access unaccepted memory because it can
>>> cause the guest to fail.
>>
>> Oh, hold on. What are the actual side effects of this?
>>
>> Once we're in the kdump kernel, any guest is already dead. So failing a guest doesn't apply, no?
>>
> Unaccepted Memory is used by virtual machines.  In this case the guest
> has kexec'ed to a dump-capture kernel, so the virtual machine is still
> alive and running the dump-capture kernel.

Ah, I got lost in TDX host semantics. So what you're saying, if we 
(guest) are reading unnaccepted memory we will get zapped. Makes sense.

-- 
Cheers,

David / dhildenb

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