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(p200300cbc74fd600c705bc2517b271c9.dip0.t-ipconnect.de. [2003:cb:c74f:d600:c705:bc25:17b2:71c9]) by smtp.gmail.com with ESMTPSA id ay7-20020a05600c1e0700b0040303a9965asm9212894wmb.40.2023.09.12.00.50.18 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 12 Sep 2023 00:50:19 -0700 (PDT) Message-ID: Date: Tue, 12 Sep 2023 09:50:18 +0200 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.13.0 Subject: Re: [PATCH V2 1/2] efi/unaccepted: Do not let /proc/vmcore try to access unaccepted memory Content-Language: en-US To: Adrian Hunter , "Kirill A. Shutemov" , Borislav Petkov , Andrew Morton , Ard Biesheuvel Cc: Dave Hansen , Vlastimil Babka , Mike Rapoport , Lorenzo Stoakes , Tom Lendacky , Baoquan He , Vivek Goyal , Dave Young , 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 References: <20230911112114.91323-1-adrian.hunter@intel.com> <20230911112114.91323-2-adrian.hunter@intel.com> <96f124d6-c1f2-adb3-1d3b-8329e85ff099@redhat.com> <1c736ca3-36e2-3225-2f98-e51149c468ef@intel.com> From: David Hildenbrand Organization: Red Hat In-Reply-To: <1c736ca3-36e2-3225-2f98-e51149c468ef@intel.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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