From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 7413023C8AE for ; Wed, 6 Aug 2025 10:58:18 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1754477899; cv=none; b=itGkMbDjMQn1lEyOTxBUsq1OB4mmGN/L3qUzdPEXV9JvOgL84qtUA7DoebRvT0OiMO3SH9lUpg6bpC9fXQ+W/qt1Og5t3ivMO4p/T3OUBw5KD2QFjWidtQ7rYznFR8iJUamYynZJmb+gYBMNyqlIfSmsKmWOa/upqLmJ8O5nd6Y= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1754477899; c=relaxed/simple; bh=9vV6D9rZRafX6ErINmAAiDv16ZiuY96suxd9anC9tBU=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=ayT8h4RIgWd0V/R5iT4XVOEQyEd29DtNH/ZBdTUwdiabVz77hwgx6ACIL82+LgSVyKd0BVrwzw1mNjRaFadEgyhhWsCUqV5aisz+sTufxt5ztgM+nvv03TUedWRFSuZ1sHl9H97FCS4ERSYUYkSEme8VAZbKt/XEiz0EOfSK4gg= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=Fk+8h164; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="Fk+8h164" Received: by smtp.kernel.org (Postfix) with ESMTPSA id C5F20C4CEE7; Wed, 6 Aug 2025 10:58:15 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1754477898; bh=9vV6D9rZRafX6ErINmAAiDv16ZiuY96suxd9anC9tBU=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=Fk+8h164x2QfKL8pa/aGXhnMZKIXXQ4Lb9ckBtxZNIqewwf9BEdIC4CLImZlBTqWl XuIxFHV4Q6jBI+7MqUL3SmY42VUCcF2b9NxuiOVuygrM/qcVfdVbxv+f9qf3qXASo+ kZO7voTduRFa+6rfVotePbUG6lzOS5DFD+gg1M8OCTXdvkU+J23t9sunL0i6mBS+Hj U+L11I0/CMWAdwFN/vLSceqIXuTjt0ZiWL+ptJwuftj0FZs3/fvSLm8UeQA9vdTzaf 7v8jldJ4g/5jwrqgzhbowcTn/F5ucIoQZ5u1JxL2c6aLsj7U4P1eDjIzLeWUArCrQM r5OADw0rWBXmg== Date: Wed, 6 Aug 2025 13:58:12 +0300 From: Mike Rapoport To: mawupeng Cc: ardb@kernel.org, akpm@linux-foundation.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] mm: ignore nomap memory during mirror init Message-ID: References: <20250717085723.1875462-1-mawupeng1@huawei.com> <9688e968-e9af-4143-b550-16c02a0b4ceb@huawei.com> <8d604308-36d3-4b55-8ddb-b33f8b586c1a@huawei.com> <113b914f-1597-41ca-b714-7ea048c3c6df@huawei.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <113b914f-1597-41ca-b714-7ea048c3c6df@huawei.com> On Tue, Aug 05, 2025 at 04:47:31PM +0800, mawupeng wrote: > > On 2025/7/22 16:17, Mike Rapoport wrote: > > Hi Ard, > > > > On Mon, Jul 21, 2025 at 03:08:48PM +1000, Ard Biesheuvel wrote: > >> On Sun, 20 Jul 2025 at 22:38, Mike Rapoport wrote: > >>> > >> ... > >>> > >>>> w/o this patch > >>>> [root@localhost ~]# lsmem --output-all > >>>> RANGE SIZE STATE REMOVABLE BLOCK NODE ZONES > >>>> 0x0000084000000000-0x00000847ffffffff 32G online yes 67584-67839 0 Movable > >>>> 0x0000085000000000-0x0000085fffffffff 64G online yes 68096-68607 0 Movable > >>>> > >>>> w/ this patch > >>>> [root@localhost ~]# lsmem --output-all > >>>> RANGE SIZE STATE REMOVABLE BLOCK NODE ZONES > >>>> 0x0000084000000000-0x00000847ffffffff 32G online yes 8448-8479 0 Normal > >>>> 0x0000085000000000-0x0000085fffffffff 64G online yes 8512-8575 0 Movable > >>> > >>> As I see the problem, you have a problematic firmware that fails to report > >>> memory as mirrored because it reserved for firmware own use. This causes > >>> for non-mirrored memory to appear before mirrored memory. And this breaks > >>> an assumption in find_zone_movable_pfns_for_nodes() that mirrored memory > >>> always has lower addresses than non-mirrored memory and you end up wiht > >>> having all the memory in movable zone. > >>> > >> > >> That assumption seems highly problematic to me on non-x86 > >> architectures: why should mirrored (or 'more reliable' in EFI speak) > >> memory always appear before ordinary memory in the physical memory > >> map? > > > > It's not really x86, although historically it probably comes from there. > > ZONE_NORMAL is always before ZONE_MOVABLE, so in order to have ZONE_NORMAL > > with mirrored (more reliable) memory, the mirrored memory should be before > > non-mirrored. > > > >>> So to workaround this firmware issue you propose a hack that would skip > >>> NOMAP regions while calculating zone_movable_pfn because your particular > >>> firmware reports the reserved mirrored memory as NOMAP. > >>> > >> > >> NOMAP is a Linux construct - the particular firmware reports a > >> 'reserved' memory region, but other more widely used memory types such > >> as EfiRuntimeServicesCode or *Data would result in an omitted region > >> as well, and can appear anywhere in the physical memory map. There is > >> no requirement for the firmware to do anything here wrt the > >> MORE_RELIABLE attribute even though such regions may be carved out of > >> a block of memory that is reported as such to the OS. > >> > >> So I agree with Wupeng Ma that there is an issue here: reporting it as > >> mirrored even though it is reserved should not be needed to prevent > >> the kernel from mishandling it. > > > > But a check for NOMAP won't actually fix it in the general case, especially > > if it can appear anywhere in the physical memory map. E.g. if there's an MR > > region followed by two reserved regions and one of these regions is not > > NOMAP and then MR region again, ZONE_NORMAL will only include the first MR > > region. > > What kind of memory is reserved and is not nomap. EFI_ACPI_RECLAIM_MEMORY is surely reserved and it won't be nomap if it can be mapped WB. I believe other types may be treated the same, I don't familiar with efi code enough to tell. > > We may want to consider scanning the entire memblock.memory to find all > > mirrored regions in a and than make a decision where to cut ZONE_NORMAL > > based on that. > > AFICT, mirrored memory should always locate at the top of numa memory > region due the linux's zone management. there maybe no good decision > based on memblock.memory rather that use the the first non-mirror > usable memory pfn to cut. Thinking out loud, if nomap is not usable to Linux why would efi add it to memblock.memory at all? -- Sincerely yours, Mike.