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(p200300cbc7435500a9bd94ab74e9782f.dip0.t-ipconnect.de. [2003:cb:c743:5500:a9bd:94ab:74e9:782f]) by smtp.gmail.com with ESMTPSA id r23-20020a05600c321700b00402b9d611d9sm5118569wmp.0.2023.09.11.01.03.37 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 11 Sep 2023 01:03:37 -0700 (PDT) Message-ID: Date: Mon, 11 Sep 2023 10:03:36 +0200 Precedence: bulk X-Mailing-List: linux-coco@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.13.0 To: Adrian Hunter , "Kirill A. Shutemov" , Borislav Petkov , Andrew Morton 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: <20230906073902.4229-1-adrian.hunter@intel.com> <20230906073902.4229-2-adrian.hunter@intel.com> From: David Hildenbrand Organization: Red Hat Subject: Re: [PATCH 1/3] proc/vmcore: Do not map unaccepted memory In-Reply-To: <20230906073902.4229-2-adrian.hunter@intel.com> X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Language: en-US Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit 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)? I recall there might be other kdump-related issues for TDX and friends to solve. Especially, which information the second kernel gets provided by the first kernel. So can this patch even be tested reasonably (IOW, get into a kdump kernel in an environment where the first kernel has unaccepted memory, and verify that unaccepted memory is handled accordingly? ... while kdump doing anything reasonable in such an environment at all?) -- Cheers, David / dhildenb