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smtp.subspace.kernel.org; dkim=pass header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=UIE+jqZK; arc=none smtp.remote-ip=100.103.45.18 Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (prime256v1)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 88C60606A32A; Thu, 12 Nov 2026 09:08:33 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=UIE+jqZK Received: by smtp.kernel.org (Postfix) with ESMTPSA id C01011F00A0A; Thu, 12 Nov 2026 09:08:26 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1794474513; bh=d0TW5g+5gf+ItcPdOWLfpHX4VmIPTaVn9u8r31nhF/E=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=UIE+jqZKYrrfRzCUJkrZMjAZk2iT+4AzaK39M6M3D3/SLhCgj65MkGDvs6u/InuwL p+SYWAtprInI/uTpnJZV/liEHwPI7EbU3xx7gP0pXYpGErDjbACmssL2pTRG91pJ7X DL/d4ADFb+TDAmC8EFy05ixD1V2CzAsINhjWcHRTbRlZfbkkGlnv924ADJldjo9P2l tz9iY/ErTV1OUvZVIiDUK972hNZ3t3Y5WLpgX9L00ZyuWOjaHfY0XaR8qLObnYnnFq 0590rXJS85TJ9/5fIc2IPUjFjNC7pDzMgUJrIGSVMYlu/dZ+D9a0E+n+sl/xG1rVt9 bdYucvLcBMoSA== Message-ID: <094479b1-a982-48f7-ac70-75260edc505f@kernel.org> Date: Thu, 12 Nov 2026 10:08:16 +0100 X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [RFC PATCH 4/5] mm/page_alloc: Keep pre-online poison out of the buddy allocator To: Shaikh Kamaluddin , Davidlohr Bueso , Jonathan Cameron , Dave Jiang , Alison Schofield , Vishal Verma , Dan Williams , Miaohe Lin , Andrew Morton , Vlastimil Babka , Breno Leitao Cc: Ira Weiny , Li Ming , Richard Cheng , Naoya Horiguchi , Suren Baghdasaryan , Michal Hocko , Brendan Jackman , Johannes Weiner , Zi Yan , linux-cxl@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, Oscar Salvador , Kiryl Shutsemau , Harry Yoo References: <20261010162017.62506-1-shaikhkamal2012@gmail.com> <20261010162017.62506-5-shaikhkamal2012@gmail.com> From: "David Hildenbrand (Arm)" Content-Language: en-US Autocrypt: addr=david@kernel.org; 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charset=UTF-8 Content-Transfer-Encoding: 7bit On 10/10/26 18:20, Shaikh Kamaluddin wrote: > The inherited-poison path checks initialized blocks before releasing > them to the buddy allocator. CXL device poison discovered before > hot-added memory is onlined is recorded separately in the pre-online > poison registry. > > Extend __free_pages_core() to send a block to free_poisoned_block() when > it intersects either poison source. In free_poisoned_block(), withhold a > page when its PFN is registered as pre-online poison or its physical > address is present in the inherited-poison table. > > Pages identified by either source continue through > hwpoison_boot_page(), while clean pages are released through > accept_and_free_block(). > > Signed-off-by: Shaikh Kamaluddin > --- > mm/page_alloc.c | 8 ++++++-- > 1 file changed, 6 insertions(+), 2 deletions(-) > > diff --git a/mm/page_alloc.c b/mm/page_alloc.c > index cca67a2702a4..57843df01b2a 100644 > --- a/mm/page_alloc.c > +++ b/mm/page_alloc.c > @@ -33,6 +33,7 @@ > #include > #include > #include > +#include > #include > #include > #include > @@ -1601,12 +1602,14 @@ static void __meminit free_poisoned_block(struct page *page, unsigned int order, > enum meminit_context context) > { > unsigned long i, nr_pages = 1UL << order; > + unsigned long pfn = page_to_pfn(page); > > for (i = 0; i < nr_pages; i++) { > struct page *p = page + i; > phys_addr_t phys = page_to_phys(p); > > - if (range_contains_poisoned_memory(phys, PAGE_SIZE)) { > + if (range_contains_poisoned_memory(phys, PAGE_SIZE) || > + preonline_hwpoison_contains(pfn + i)) { > hwpoison_boot_page(p, context); > continue; > } > @@ -1652,7 +1655,8 @@ void __meminit __free_pages_core(struct page *page, unsigned int order, > > /* First: a block parked by __free_unaccepted() never returns here. */ > if (range_contains_poisoned_memory(page_to_phys(page), > - PAGE_SIZE << order)) { > + PAGE_SIZE << order) || > + preonline_hwpoison_intersects(page_to_pfn(page), nr_pages)) { That looks rather hacky as well. I really don't want us to have various source of poison information that the page allocator + core-mm has to mess with. It's just very bad design. I made that clear in the last kexec attempt to do something similar. This likely belongs into memory onlining, which could online only the relevant, un-poisoned pageblocks. Not sure how it would best retrieve that information, but we should definitely not add more shaky hwpoison sources to random pieces of core kernel code. -- Cheers, David