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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: <20230911100555.mjjnx3ujnjlaxgsy@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> <20230911092712.2ps55mylf7elfqp6@box.shutemov.name> <476456e1-ac50-8e48-260d-5cbe5e8b085e@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <476456e1-ac50-8e48-260d-5cbe5e8b085e@redhat.com> X-Rspam-User: X-Stat-Signature: i45fhqjsuag9hy4fso1pqtmsmyngbyk5 X-Rspamd-Server: rspam07 X-Rspamd-Queue-Id: 768D98000A X-HE-Tag: 1694426765-329220 X-HE-Meta: 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 UxZ1vCIf gcCqXfTEL+7U0nIQ4y32wi99BbsohnsnBIoFJNab2B+ta3JECnKLCquHICyUXYOZjMfaqHG3jRvFlL0BSe+iyGJirvh7uL9BLl4nyXZ0FC79QRzE= 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 11:50:31AM +0200, David Hildenbrand wrote: > 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? Can do. But the other two patches are not related to kexec. Hm. -- Kiryl Shutsemau / Kirill A. Shutemov