From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 8ABBE410D04; Tue, 30 Jun 2026 12:46:35 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1782823596; cv=none; b=TpgCSDmKJB3/Hxxf+KgHi/bc+duQZMvBYt+YiZSScWxiKk2hweL1iJKKjx/isfcINWQ3yR/HrYE5n637j/ZyQ+0Ea8WX7GndM1g2IEabQFut1wu0G+BtkTL6Zr+hfADLFPiQI9KDZyB8/1+rJgGYKOT8z7U5gFueoYiE4yBGpUQ= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1782823596; c=relaxed/simple; bh=RT0dwjn0lBQ3vrq53HCmpzrU5ySV3XD8Calq9B5BmuA=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=S1K2kG0YBWH3k1pXtnFFjp11z6Kp3MykBeW//ylEnTh/M9eMSQBo9XPSa6saXcKgExm54fLX9NxLWPSvIu2T8lQcIOw1HBpjaFo+UScFoCuJICl8f9uJjaQp/Xyc6U39uNwXB7beAP32ErFy2B6F5QL56yKDilrACObhxsoZxJo= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=l9fHtvOQ; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="l9fHtvOQ" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 172481F000E9; Tue, 30 Jun 2026 12:46:28 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1782823595; bh=zVRDifu1QOyyXsAGZkUm6ew4XqjId6qSZyoyYBdxCL4=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=l9fHtvOQOP1Ai0VpWvZKiub+ksLWhWziADe3pLNfPxthadvVrmehxH6q/40yTMPH1 VKlXtQcRFJUncsgox7z1MmPK+41arWoWSKb15luQrC+c7RZwPSRh6YaHuQHVDlr2zP gE8n346B54Meo0ciXzFd11xIDgLQSmDXCrxIp2W8SKL2lQh5UiOZ7YltjkSkgnWpY4 EK8BYZHlvO7zQkCqxwftcbSy93CqfKyBZyqQhAuzUVHKqA45XL81fXEVvoJ4dwFkfn DFgd9gCeYXOIecVHrqwaum6X/8FjP9lDctXz4DYecsPkUmIuLDbc5l7elbP5B9KEUA WAar42Kf9ZP1Q== Message-ID: <1fb04774-1ac6-472a-bbc8-52fceb69b018@kernel.org> Date: Tue, 30 Jun 2026 14:46:27 +0200 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 4/5] mm/page_vma_mapped: use huge_ptep_get() for hugetlb To: Dev Jain , Lance Yang Cc: linmiaohe@huawei.com, muchun.song@linux.dev, osalvador@suse.de, akpm@linux-foundation.org, ljs@kernel.org, liam@infradead.org, riel@surriel.com, vbabka@kernel.org, harry@kernel.org, jannh@google.com, kas@kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, rcampbell@nvidia.com, apopple@nvidia.com, ziy@nvidia.com, matthew.brost@intel.com, joshua.hahnjy@gmail.com, rakie.kim@sk.com, byungchul@sk.com, gourry@gourry.net, ying.huang@linux.alibaba.com, mel@csn.ul.ie, nao.horiguchi@gmail.com, ak@linux.intel.com, j-nomura@ce.jp.nec.com, pfalcato@suse.de, dave.hansen@intel.com, tglx@kernel.org, jpoimboe@kernel.org, ryan.roberts@arm.com, anshuman.khandual@arm.com, stable@vger.kernel.org References: <0fabee2a-edb7-41c8-91ec-8cf0646c9e83@kernel.org> <20260629074802.42727-1-lance.yang@linux.dev> <6fdc0cbd-0880-4594-bf33-a2993ac2fe60@arm.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 6/30/26 13:34, Dev Jain wrote: > > > On 29/06/26 1:35 pm, David Hildenbrand (Arm) wrote: >> On 6/29/26 09:48, Lance Yang wrote: >>> >>> >from pagewalk code (where some users like pagemap need the actual address). >>> >>> Indeed ... >>> >>> >>> Kinda lean toward option 1, even if it's more invasive. If we pass the >>> hstate down, each arch can figure out the right addr from there. >>> >>> >>> AFAICT, for huge_ptep_get() the addr users are arm64 and powerpc, riscv >>> doesn't really care about addr there. Looks mostly arm64-specific ... >> powerpc handles it correctly in the weird "span two PMD entries" case by >> aligning the PMD down. >> >> Risc-v copied from arm64, but can simply derive the #entries from the PTE value. >> it doesn't have to re-walk the table using the address. >> >> But I think the following is required to fix, no? > > We don't receive an unaligned ptep in huge_ptep_get, and riscv derives the > number of cont ptes from the pte itself, so why is the below required? Let me look at the actual report once more ... I thought for a second that the problem would be having the ptep not point at the start of the hugetlb page mapping. But that should always be the case. So yes, riscv does not have any problems. And IIUC, arm64 only has a problem when CONT_PTES != CONT_PMDS (16 kernel?). Yeah, aligning the ptep down doesn't solve anything, it's already properly aligned. To fix it inside arm64 code, we'd have to teach find_num_contig() to ignore the ptep and instead look for the cont bit, maybe? But I'm sure I messed this up as I am working on 10 things at the same time :D diff --git a/arch/arm64/mm/hugetlbpage.c b/arch/arm64/mm/hugetlbpage.c index d477a9dd1b472..d1d03795c135e 100644 --- a/arch/arm64/mm/hugetlbpage.c +++ b/arch/arm64/mm/hugetlbpage.c @@ -76,7 +76,7 @@ bool arch_hugetlb_migration_supported(struct hstate *h) #endif static int find_num_contig(struct mm_struct *mm, unsigned long addr, - pte_t *ptep, size_t *pgsize) + size_t *pgsize) { pgd_t *pgdp = pgd_offset(mm, addr); p4d_t *p4dp; @@ -87,7 +87,7 @@ static int find_num_contig(struct mm_struct *mm, unsigned long addr, p4dp = p4d_offset(pgdp, addr); pudp = pud_offset(p4dp, addr); pmdp = pmd_offset(pudp, addr); - if ((pte_t *)pmdp == ptep) { + if (pmd_cont(*pmdp)) { *pgsize = PMD_SIZE; return CONT_PMDS; } @@ -131,7 +131,7 @@ pte_t huge_ptep_get(struct mm_struct *mm, unsigned long addr, pte_t *ptep) if (!pte_present(orig_pte) || !pte_cont(orig_pte)) return orig_pte; - ncontig = find_num_contig(mm, addr, ptep, &pgsize); + ncontig = find_num_contig(mm, addr, &pgsize); for (i = 0; i < ncontig; i++, ptep++) { pte_t pte = __ptep_get(ptep); @@ -475,7 +475,7 @@ void huge_ptep_set_wrprotect(struct mm_struct *mm, return; } - ncontig = find_num_contig(mm, addr, ptep, &pgsize); + ncontig = find_num_contig(mm, addr, &pgsize); pte = get_clear_contig_flush(mm, addr, ptep, pgsize, ncontig); pte = pte_wrprotect(pte); diff --git a/mm/memory.c b/mm/memory.c -- Cheers, David