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Sun, 23 Feb 2025 17:31:31 -0800 (PST) Date: Mon, 24 Feb 2025 01:31:31 +0000 From: Wei Yang To: Mike Rapoport Cc: Wei Yang , linux-kernel@vger.kernel.org, Alexander Graf , Andrew Morton , Andy Lutomirski , Anthony Yznaga , Arnd Bergmann , Ashish Kalra , Benjamin Herrenschmidt , Borislav Petkov , Catalin Marinas , Dave Hansen , David Woodhouse , Eric Biederman , Ingo Molnar , James Gowans , Jonathan Corbet , Krzysztof Kozlowski , Mark Rutland , Paolo Bonzini , Pasha Tatashin , "H. Peter Anvin" , Peter Zijlstra , Pratyush Yadav , Rob Herring , Rob Herring , Saravana Kannan , Stanislav Kinsburskii , Steven Rostedt , Thomas Gleixner , Tom Lendacky , Usama Arif , Will Deacon , devicetree@vger.kernel.org, kexec@lists.infradead.org, linux-arm-kernel@lists.infradead.org, linux-doc@vger.kernel.org, linux-mm@kvack.org, x86@kernel.org Subject: Re: [PATCH v4 02/14] memblock: add MEMBLOCK_RSRV_KERN flag Message-ID: <20250224013131.fzz552bn7fs64umq@master> Reply-To: Wei Yang References: <20250206132754.2596694-1-rppt@kernel.org> <20250206132754.2596694-3-rppt@kernel.org> <20250218155004.n53fcuj2lrl5rxll@master> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: NeoMutt/20170113 (1.7.2) X-Rspamd-Server: rspam04 X-Rspamd-Queue-Id: A6B6940006 X-Stat-Signature: 343nhwrbfy4y8bgxstmybski9fwq4zam X-Rspam-User: X-HE-Tag: 1740360694-174761 X-HE-Meta: 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 qO5AkiGp 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 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 Wed, Feb 19, 2025 at 09:24:31AM +0200, Mike Rapoport wrote: >Hi, > >On Tue, Feb 18, 2025 at 03:50:04PM +0000, Wei Yang wrote: >> On Thu, Feb 06, 2025 at 03:27:42PM +0200, Mike Rapoport wrote: >> >From: "Mike Rapoport (Microsoft)" >> > >> >to denote areas that were reserved for kernel use either directly with >> >memblock_reserve_kern() or via memblock allocations. >> > >> >Signed-off-by: Mike Rapoport (Microsoft) >> >--- >> > include/linux/memblock.h | 16 +++++++++++++++- >> > mm/memblock.c | 32 ++++++++++++++++++++++++-------- >> > 2 files changed, 39 insertions(+), 9 deletions(-) >> > >> >diff --git a/include/linux/memblock.h b/include/linux/memblock.h >> >index e79eb6ac516f..65e274550f5d 100644 >> >--- a/include/linux/memblock.h >> >+++ b/include/linux/memblock.h >> >@@ -50,6 +50,7 @@ enum memblock_flags { >> > MEMBLOCK_NOMAP = 0x4, /* don't add to kernel direct mapping */ >> > MEMBLOCK_DRIVER_MANAGED = 0x8, /* always detected via a driver */ >> > MEMBLOCK_RSRV_NOINIT = 0x10, /* don't initialize struct pages */ >> >+ MEMBLOCK_RSRV_KERN = 0x20, /* memory reserved for kernel use */ >> >> Above memblock_flags, there are comments on explaining those flags. >> >> Seems we miss it for MEMBLOCK_RSRV_KERN. > >Right, thanks! > >> > >> > #ifdef CONFIG_HAVE_MEMBLOCK_PHYS_MAP >> >@@ -1459,14 +1460,14 @@ phys_addr_t __init memblock_alloc_range_nid(phys_addr_t size, >> > again: >> > found = memblock_find_in_range_node(size, align, start, end, nid, >> > flags); >> >- if (found && !memblock_reserve(found, size)) >> >+ if (found && !__memblock_reserve(found, size, nid, MEMBLOCK_RSRV_KERN)) >> >> Maybe we could use memblock_reserve_kern() directly. If my understanding is >> correct, the reserved region's nid is not used. > >We use nid of reserved regions in reserve_bootmem_region() (commit >61167ad5fecd ("mm: pass nid to reserve_bootmem_region()")) but KHO needs to >know the distribution of reserved memory among the nodes before >memmap_init_reserved_pages(). > >> BTW, one question here. How we handle concurrent memblock allocation? If two >> threads find the same available range and do the reservation, it seems to be a >> problem to me. Or I missed something? > >memblock allocations end before smp_init(), there is no possible concurrency. > Thanks, I still have one question here. Below is a simplified call flow. mm_core_init() mem_init() memblock_free_all() free_low_memory_core_early() memmap_init_reserved_pages() memblock_set_node(..., memblock.reserved, ) --- (1) __free_memory_core() kmem_cache_init() slab_state = UP; --- (2) And memblock_allloc_range_nid() is not supposed to be called after slab_is_available(). Even someone do dose it, it will get memory from slab instead of reserve region in memblock. >From the above call flow and background, there are three cases when memblock_alloc_range_nid() would be called: * If it is called before (1), memblock.reserved's nid would be adjusted correctly. * If it is called after (2), we don't touch memblock.reserved. * If it happens between (1) and (2), it looks would break the consistency of nid information in memblock.reserved. Because when we use memblock_reserve_kern(), NUMA_NO_NODE would be stored in region. So my question is if the third case happens, would it introduce a bug? If it won't happen, seems we don't need to specify the nid here? -- Wei Yang Help you, Help me