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b=eGaUrFBycjIxreSz5k8O47OfOVXtrnqaQYRaseR+2Q1urnt/g9M7QSF+wY+bV6+7W c6fyrD9bkONk+3gILyKLscIKyA8XQh8eZJjOqtCT6alE7fWfXE48w7QYpkJw/BarBn rRgtfCrLhUXqB98oB+T3H3ANZsGQ/OaWsfeDJn586cIWRqokJQqO2GBZlA1hhIbUeR p7jMQlRnN8ZR23ryoaJCo2NbCebuK3JHlawmTbKFJmkDf5B/sqU+PWBjUrlM3PSGY8 Suh/GdmqS/JWaZtgSncYTGoM+loAt0EC1jtcX0lMKNcxbq/LbxCP5f7kgyzA64GJa5 i4BspvJG+rBlg== From: Sasha Levin To: stable@vger.kernel.org, cuichao1753@phytium.com.cn Cc: Jonathan Cameron , Gregory Price , Dan Williams , "Mike Rapoport (Microsoft)" , linux-mm@kvack.org Subject: FAILED: Patch "mm: numa_memblks: Identify the accurate NUMA ID of CFMW" failed to apply to 6.12-stable tree Date: Sat, 28 Feb 2026 20:28:31 -0500 Message-ID: <20260301012832.1686293-1-sashal@kernel.org> X-Mailer: git-send-email 2.51.0 MIME-Version: 1.0 X-Patchwork-Hint: ignore X-stable: review Content-Transfer-Encoding: 8bit X-Rspamd-Server: rspam02 X-Rspamd-Queue-Id: AD1F7C0005 X-Stat-Signature: 6k4iedxzqkrmq8tepkif4or1dwnnd1ry X-Rspam-User: X-HE-Tag: 1772328514-826117 X-HE-Meta: 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 7NcDvRZ6 LqKCH Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: The patch below does not apply to the 6.12-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to . Thanks, Sasha ------------------ original commit in Linus's tree ------------------ >From f043a93fff9e3e3e648b6525483f59104b0819fa Mon Sep 17 00:00:00 2001 From: Cui Chao Date: Fri, 13 Feb 2026 14:03:47 +0800 Subject: [PATCH] mm: numa_memblks: Identify the accurate NUMA ID of CFMW In some physical memory layout designs, the address space of CFMW (CXL Fixed Memory Window) resides between multiple segments of system memory belonging to the same NUMA node. In numa_cleanup_meminfo, these multiple segments of system memory are merged into a larger numa_memblk. When identifying which NUMA node the CFMW belongs to, it may be incorrectly assigned to the NUMA node of the merged system memory. When a CXL RAM region is created in userspace, the memory capacity of the newly created region is not added to the CFMW-dedicated NUMA node. Instead, it is accumulated into an existing NUMA node (e.g., NUMA0 containing RAM). This makes it impossible to clearly distinguish between the two types of memory, which may affect memory-tiering applications. Example memory layout: Physical address space: 0x00000000 - 0x1FFFFFFF System RAM (node0) 0x20000000 - 0x2FFFFFFF CXL CFMW (node2) 0x40000000 - 0x5FFFFFFF System RAM (node0) 0x60000000 - 0x7FFFFFFF System RAM (node1) After numa_cleanup_meminfo, the two node0 segments are merged into one: 0x00000000 - 0x5FFFFFFF System RAM (node0) // CFMW is inside the range 0x60000000 - 0x7FFFFFFF System RAM (node1) So the CFMW (0x20000000-0x2FFFFFFF) will be incorrectly assigned to node0. To address this scenario, accurately identifying the correct NUMA node can be achieved by checking whether the region belongs to both numa_meminfo and numa_reserved_meminfo. While this issue is only observed in a QEMU configuration, and no known end users are impacted by this problem, it is likely that some firmware implementation is leaving memory map holes in a CXL Fixed Memory Window. CXL hotplug depends on mapping free window capacity, and it seems to be only a coincidence to have not hit this problem yet. Fixes: 779dd20cfb56 ("cxl/region: Add region creation support") Signed-off-by: Cui Chao Cc: stable@vger.kernel.org Reviewed-by: Jonathan Cameron Reviewed-by: Gregory Price Reviewed-by: Dan Williams Link: https://patch.msgid.link/20260213060347.2389818-2-cuichao1753@phytium.com.cn Signed-off-by: Mike Rapoport (Microsoft) --- mm/numa_memblks.c | 9 +++++---- 1 file changed, 5 insertions(+), 4 deletions(-) diff --git a/mm/numa_memblks.c b/mm/numa_memblks.c index 8f5735fda0a21..3f53464240e8d 100644 --- a/mm/numa_memblks.c +++ b/mm/numa_memblks.c @@ -570,15 +570,16 @@ static int meminfo_to_nid(struct numa_meminfo *mi, u64 start) int phys_to_target_node(u64 start) { int nid = meminfo_to_nid(&numa_meminfo, start); + int reserved_nid = meminfo_to_nid(&numa_reserved_meminfo, start); /* - * Prefer online nodes, but if reserved memory might be - * hot-added continue the search with reserved ranges. + * Prefer online nodes unless the address is also described + * by reserved ranges, in which case use the reserved nid. */ - if (nid != NUMA_NO_NODE) + if (nid != NUMA_NO_NODE && reserved_nid == NUMA_NO_NODE) return nid; - return meminfo_to_nid(&numa_reserved_meminfo, start); + return reserved_nid; } EXPORT_SYMBOL_GPL(phys_to_target_node); -- 2.51.0