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b=YW+c4kfO6iVUIhxBhnUx9AMimsxobF81pwBpnyQ0SE5E7ELvWmZdkfeto7vwKO9jq 6pfvL+Cjs/zRk8dKyK8FH3SBte060/4efJu+6WPW5gqUVS7doAeda5u4823Pi023DS xSZ4J/a/A52yUL+0jAMbSqNBdb5bPoPsJslMJWDztDUguK7z0qX4D48MemjMXuhf85 AABeg3ebvYkxWOGU/om+RSgSI+PV5rsz5/PN3cvtuA/LRwgy8Q3wEZG1Uma+J0C0Hx mwu9p4LHmHq3C+bZ43Yg2AFe8sDP+W4iDit7LlDX3xtJVyjUr+tLkWXA78uG7Q9Isw 7bMMhv3lMwXSg== Date: Sun, 10 Aug 2025 11:14:53 +0300 From: Mike Rapoport To: Ard Biesheuvel Cc: mawupeng , 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: <9688e968-e9af-4143-b550-16c02a0b4ceb@huawei.com> <8d604308-36d3-4b55-8ddb-b33f8b586c1a@huawei.com> <113b914f-1597-41ca-b714-7ea048c3c6df@huawei.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Stat-Signature: 6s9fr1ep8tyuas7ua86ceekgzx5i55ff X-Rspamd-Server: rspam01 X-Rspamd-Queue-Id: 3128540004 X-Rspam-User: X-HE-Tag: 1754813700-906883 X-HE-Meta: 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 mLoMY6gi vEFxbAh/k3RTf0Lrrf3+iUJFDapIyQkcZfcm5ZwmHrPLVtEwNj1cOGbNn2E4EMZx6vM+JxoJ8jPbwFCMPr/6wayaQ0Ibq7tu2ssd9lzS1fQfglG1BQxCsOY2Sy9EdTYsNSIPBbcfYXwHxsEsRkxedaZ2ewFexz21pArtqCP34X8mNKsYc43wNXMSQlowrTvxfHZtzTsYQLNEkt/PUbZDCIWkdTotobFZxhjXDKtjcOS+7X0G86c79j5M636MnG+N6MKT9ztdjxJIbfddVSBhIvNt10g== 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: List-Subscribe: List-Unsubscribe: On Sun, Aug 10, 2025 at 03:14:03PM +1000, Ard Biesheuvel wrote: > On Wed, 6 Aug 2025 at 20:58, Mike Rapoport wrote: > > > > 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? > > > > Because the region has RAM semantics and not MMIO semantics. This is > important on architectures such as arm64, where mapping RAM with > device attributes breaks cache coherency. Right, such regions should not be mapped. But this can be achieved with not memblock_add'ing them at the first place, like e820 does for example. -- Sincerely yours, Mike.