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Mon, 28 Sep 2026 10:12:33 +0000 X-Mizu-Trace-ID: 52ca14a05b391034 X-Migadu-Flow: FLOW_OUT Date: Mon, 28 Sep 2026 18:12:30 +0800 From: Baoquan He To: "David Hildenbrand (Arm)" Cc: Andrew Morton , David Carlier , Dave Young , linux-kernel@vger.kernel.org, linux-mm@kvack.org Subject: Re: [PATCH] vmcoreinfo: export SECTION_HAS_MEM_MAP Message-ID: References: <20260928-section_has_mem_map-v1-1-4129f6ba2838@kernel.org> <21abd60c-e71b-40ed-9506-853d4485cf4b@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <21abd60c-e71b-40ed-9506-853d4485cf4b@kernel.org> X-Rspamd-Server: rspam06 X-Stat-Signature: ab7caddtr5bcieji67m47dnoe3b5ga1g X-Rspam-User: X-Rspamd-Queue-Id: 6FCA180008 X-HE-Tag: 1790590365-595110 X-HE-Meta: U2FsdGVkX18CR/jPrTNwQOhYLf201IpY3YWcmQ6c/71CJ+9xmX/EjkoQNLUpqFpZYKtOp/JxtJPLW4VwAYHmeM+Q0CZEIFsbcBRhJnee/hbS0r4Ijk05q4R5eY4KfC0O0r4kxiE1pv3XfxdMPxKUwtQtX3mWe4jkczELBn1FYE0mNzA3nwmukN4iQbU5MBo36SUmJzper/x10tva/avmg4gJ6jZBiweYxKyPHixmL/aFH3Snkz81TVNorOVqtsuiZ+/MPDRYgCCTd97m/c0u4FkWt0b3sP09WRFnghI+BnsyFgW4H1D4VYViFUrqQGcECr6xnIoDoEpVeA8jNMF5Ico5C2KeNyGhRi3QVzwOGdPtD7xOC56/CnOjhi9PLNdhprm1PF5Jhgq2Dg/iJzRrTTkyL1UBMaF91mHQyZdCT04PIqZVhreIRSXCWfF41hXhBJne7+JPiStY//wEeWL7AU1SMEZamyZ5U78zWXqBivyCjiBn/N972grVrrrqzsu+vcNIv7fGJvsrbtIRJ1iyasPBdwr4c88lcMLi0uhiji/BMcqVuTqGzXoxszA0wtK5RlbNJByJ4I3R4rfTS5+7Ue59TxrN8IpDGAjiS/1hnaih6DLIEZYcOdqKAJ3TmkeSf6s+HHXPH8mlJnGFXtidcL780+8UEqFml9bqDWf8b9hmv92qsWQ5TTsnmv2n9vQRiOxl0H/3aIWq2HdPpnCSqemRoAhj7/rCS8ehhLHY31OpFCzMIyoZaN2WBZh1it5nh2VM+7xrKS2EcSWIi/9XMOQsFgqOOaV9U5gk26Glk72rhhIJ8a21+Pm+9UApoGOLboutdS/6WDO3N40znvixI363wGYjm7JEH6nCsGMIfqm4EzyeulKmxsz+pv8TDyhSVW6G+0Mw1pMy1QQoT0J8lx7u56WTRj8gBVu+A09dzDq+r+EPZnEv6I7D9AY/W4+mDZRD4CweDc9Hty3lygd SRFkAOYn +jGG/B+s3/r5LVkps9yLYCXDCMXi05G1261i5ad7MT57tWpQlscdtR/fglPgWDj2vBu4TMiO5E/SokNeg1CvrwZCHkl5sY7HGKBC+4jSQeH0/PdWwDVtrLrabeaFjPy+fQ5atcH5mftscxw2/jFEDm3xaRevBzdkC8TsVPLRRXL3HNtcDkU3mX6u0Mci+esUPGmAaYFSaFLAzYY3Oki2p1qzsx3ZHw3qgI80QsZNu3e5j5aQMsRc9vB+CzRM3k6/ZOSClSreDQoXe9tDev1iQHxo4eL5JKCPulzmhmOusuq8WYmlLZk02/rMnJJ4PizAfktf8+rBcBXt/cHDsgGpcd/uriZgMCAmzGwQ3n/e1s3aSsL2b9/x7FJdxuA== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 09/28/26 at 11:14am, David Hildenbrand (Arm) wrote: > On 9/28/26 11:11, Baoquan He wrote: > > On 09/28/26 at 10:48am, David Hildenbrand (Arm) wrote: > >> The crash tool currently hardcodes SECTION_HAS_MEM_MAP, and makedumpfile > >> needs similar information (although still relying on > >> SECTION_MARKED_PRESENT, it should switch to SECTION_HAS_MEM_MAP). > >> > >> Let's just export the value instead, so tools that work on vmcoreinfo > >> will not have to guess. > >> > >> Signed-off-by: David Hildenbrand (Arm) > >> --- > >> Result of the discussion in reply to "[PATCH v2 00/13] mm/sparse: remove > >> SECTION_MARKED_PRESENT and further cleanups" [1] > >> > >> This patch can go in independently. It would be preferable if both > >> go into the same kernel release ;) > >> > >> [1] https://lore.kernel.org/r/20260921-b4-sparsemem_cleanups-v2-0-54d81d65e125@kernel.org > >> --- > >> kernel/vmcore_info.c | 1 + > >> 1 file changed, 1 insertion(+) > >> > >> diff --git a/kernel/vmcore_info.c b/kernel/vmcore_info.c > >> index 5a417f8a922a..7833a36064a8 100644 > >> --- a/kernel/vmcore_info.c > >> +++ b/kernel/vmcore_info.c > >> @@ -182,6 +182,7 @@ static int __init crash_save_vmcoreinfo_init(void) > >> VMCOREINFO_STRUCT_SIZE(mem_section); > >> VMCOREINFO_OFFSET(mem_section, section_mem_map); > >> VMCOREINFO_NUMBER(SECTION_SIZE_BITS); > >> + VMCOREINFO_NUMBER(SECTION_HAS_MEM_MAP); > >> VMCOREINFO_NUMBER(MAX_PHYSMEM_BITS); > >> #endif > >> VMCOREINFO_STRUCT_SIZE(page); > > > > It would be good to add one section in > > Documentation/admin-guide/kdump/vmcoreinfo.rst, e.g > > > > SECTION_HAS_MEM_MAP > > ------------------- > > > > Indicates a memory section has struct page array (mem_map). User-space > > tools should read this value but not hardcode it since the bit position > > could change between kernel versions. > > I'm not particularly happy about having core-kernel defines documented in > kdump/vmcoreinfo.rst, though? > > If it would be something vmcoreinfo special, sure. But not for basic defines. > > "See the kernel source code" is really what anybody using this should be doing? I can't remember who suggested adding this document. The benefit is users can read document to understand how it works, no need to look at the code. I don't have strong preference on this. So I am fine with both. Or we can add it if anyone really complains. For the patch itself, Acked-by: Baoquan He Thanks Baoquan