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Fri, 14 Apr 2023 06:19:05 -0400 (EDT) Received: by box.shutemov.name (Postfix, from userid 1000) id EE51510D7B4; Fri, 14 Apr 2023 13:19:01 +0300 (+03) Date: Fri, 14 Apr 2023 13:19:01 +0300 From: "Kirill A. Shutemov" To: Vlastimil Babka Cc: "Kirill A. Shutemov" , Borislav Petkov , Andy Lutomirski , Sean Christopherson , Andrew Morton , Joerg Roedel , Ard Biesheuvel , Andi Kleen , Kuppuswamy Sathyanarayanan , David Rientjes , Tom Lendacky , Thomas Gleixner , Peter Zijlstra , Paolo Bonzini , Ingo Molnar , Dario Faggioli , Dave Hansen , Mike Rapoport , David Hildenbrand , Mel Gorman , marcelo.cerri@canonical.com, tim.gardner@canonical.com, khalid.elmously@canonical.com, philip.cox@canonical.com, aarcange@redhat.com, peterx@redhat.com, x86@kernel.org, linux-mm@kvack.org, linux-coco@lists.linux.dev, linux-efi@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCHv9 03/14] mm/page_alloc: Fake unaccepted memory Message-ID: <20230414101901.j3zoji6vmjzpjiec@box> References: <20230330114956.20342-1-kirill.shutemov@linux.intel.com> <20230330114956.20342-4-kirill.shutemov@linux.intel.com> <835dfe65-d9dd-0b16-37d4-920e97f1bca0@suse.cz> <20230403143915.uc4tnpgmssvpdqxu@box.shutemov.name> <20230403155011.aodnd5ratcyeie52@box.shutemov.name> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20230403155011.aodnd5ratcyeie52@box.shutemov.name> X-Rspam-User: X-Rspamd-Server: rspam02 X-Rspamd-Queue-Id: 5892E40015 X-Stat-Signature: ksjaju79jo5rqukxn8b9er35hrhun9hk X-HE-Tag: 1681467549-604651 X-HE-Meta: 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 oXC5XLv6 9l04pwTRMdxwvLBYPrZ2PEWkw3DV+vnNGwKb13f78xnC11giUS201F5z3ppOFoE2bPYHMSOiV3FBTlH9R/queuOgR1R5NFGQ1IGD8DYjzxhH7tNi/72G7tbV4SXyXAztzHdyVljmzKqD+iucqNlqIqLlFuC2p931wYcnN7IjBSp8iUTL071IYRN4Ox3OimF4BoxeiCg2yyt0ztkXAMGD1zhoH8hu/GD1DFkWDmvbN2yDuM4UA01VsyRYJ+MOxKRB8sX2+73jHBii1kPftHfog0x8Midch/bIV0TQgh5Zku20wYk15kpg++6tz4uhtTxE00afvbZPUG4Cl88s= 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, Apr 03, 2023 at 06:50:11PM +0300, Kirill A. Shutemov wrote: > On Mon, Apr 03, 2023 at 05:39:15PM +0300, Kirill A. Shutemov wrote: > > On Mon, Apr 03, 2023 at 03:39:53PM +0200, Vlastimil Babka wrote: > > > On 3/30/23 13:49, Kirill A. Shutemov wrote: > > > > For testing purposes, it is useful to fake unaccepted memory in the > > > > system. It helps to understand unaccepted memory overhead to the page > > > > allocator. > > > > > > Ack on being useful for testing, but the question is if we want to also > > > merge this patch into mainline as it is? > > > > I don't insist on getting it upstream, but it can be handy to debug > > related bugs in the future. > > > > > > The patch allows to treat memory above the specified physical memory > > > > address as unaccepted. > > > > > > > > The change only fakes unaccepted memory for page allocator. Memblock is > > > > not affected. > > > > > > > > It also assumes that arch-provided accept_memory() on already accepted > > > > memory is a nop. > > > > > > I guess to be in mainline it would have to at least gracefully handle the > > > case of accept_memory actually not being a nop, and running on a system with > > > actual unaccepted memory (probably by ignoring the parameter in such case). > > > Then also the parameter would have to be documented. > > > > As it is written now, accept_memory() is nop on system with real > > unaccepted memory if the memory is already accepted. Arch-specific code > > will check against own records to see if the memory needs accepting. If > > not, just return. > > > > And the option will not interfere with unaccepted memory declared by EFI > > memmap. It can extend it, but that's it. > > > > Looks safe to me. > > > > > Speaking of documented parameters, I found at least two that seem a more > > > generic variant of this (but I didn't look closely if that makes sense): > > > > > > efi_fake_mem= nn[KMG]@ss[KMG]:aa[,nn[KMG]@ss[KMG]:aa,..] [EFI; X86] > > > Add arbitrary attribute to specific memory range by > > > updating original EFI memory map. > > As of now, efi_fake_mem= can adjust attributes of memory. Unaccepted is > type of memory, not an attribute. I guess we can allow it override type > too. But syntax is going to be fun. efi_fake_mem applied too late. Bitmap that represents unaccepted memory for kernel created at kernel decompression stage, but efi_fake_mem= handled in main kernel. I don't think pushing efi_fake_mem to decompressor makes sesne. I would rather drom the feature altogether. -- Kiryl Shutsemau / Kirill A. Shutemov