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Shutemov" To: David Hildenbrand Cc: Adrian Hunter , Borislav Petkov , Andrew Morton , 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 Subject: Re: [PATCH 1/3] proc/vmcore: Do not map unaccepted memory Message-ID: <20230911092712.2ps55mylf7elfqp6@box.shutemov.name> References: <20230906073902.4229-1-adrian.hunter@intel.com> <20230906073902.4229-2-adrian.hunter@intel.com> <20230911084148.l6han7jxob42rdvm@box.shutemov.name> <49ab74c8-553b-b3d0-6a72-2d259a2b5bdf@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <49ab74c8-553b-b3d0-6a72-2d259a2b5bdf@redhat.com> X-Rspamd-Server: rspam09 X-Rspamd-Queue-Id: E962B100011 X-Stat-Signature: eokiyrw8zfgep4xustxddh9zui5qoq93 X-Rspam-User: X-HE-Tag: 1694424440-134879 X-HE-Meta: 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 bTAdSHkl DfipOz/jcZkRHgA68ZPQoMpTPcA4/nluSigcGqv/G3KE1pfM/+PKMffQe3t82Es4nUXLT5EBcXmqegyB/bzRgn5oUxgOuJavUCZqQg2pR8OdEXBU= X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: 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. -- Kiryl Shutsemau / Kirill A. Shutemov