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Mon, 10 Mar 2025 02:51:33 -0700 (PDT) Received: from localhost ([185.92.221.13]) by smtp.gmail.com with ESMTPSA id a640c23a62f3a-ac255589a30sm594247266b.107.2025.03.10.02.51.25 (version=TLS1_2 cipher=ECDHE-ECDSA-CHACHA20-POLY1305 bits=256/256); Mon, 10 Mar 2025 02:51:25 -0700 (PDT) Date: Mon, 10 Mar 2025 09:51:24 +0000 From: Wei Yang To: Wei Yang Cc: Mike Rapoport , 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: <20250310095124.pa7dwgqhxglqrfes@master> Reply-To: Wei Yang References: <20250206132754.2596694-1-rppt@kernel.org> <20250206132754.2596694-3-rppt@kernel.org> <20250218155004.n53fcuj2lrl5rxll@master> <20250223002229.xuk6xlp23zr72hkc@master> Precedence: bulk X-Mailing-List: devicetree@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: <20250223002229.xuk6xlp23zr72hkc@master> User-Agent: NeoMutt/20170113 (1.7.2) On Sun, Feb 23, 2025 at 12:22:29AM +0000, Wei Yang wrote: >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(). >> > >I took another look into this commit. There maybe a very corner case in which >will leave a reserved region with no nid set. > >memmap_init_reserved_pages() > for_each_mem_region() { > ... > memblock_set_node(start, end, &memblock.reserved, nid); > } > >We leverage the iteration here to set nid to all regions in memblock.reserved. >But memblock_set_node() may call memblock_double_array() to expand the array, >which may get a range before current start. So we would miss to set the >correct nid to the new reserved region. > >I have tried to create a case in memblock test. This would happen when there >are 126 memblock.reserved regions. And the last region is across the last two >node. > >One way to fix this is compare type->max in memblock_set_node(). Then check >this return value in memmap_init_reserved_pages(). If we found the size >changes, repeat the iteration. > >But this is a very trivial one, not sure it worth fix. > Hi, Mike I have done a user space test which shows we may have a chance to leave a region with non-nid set. Not sure you are ok with my approach of fixing. -- Wei Yang Help you, Help me