From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by smtp.subspace.kernel.org (Postfix) with ESMTP id 8A6A93A16A0; Fri, 26 Jun 2026 04:06:35 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=217.140.110.172 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1782446797; cv=none; b=Qlp3+q59WkXRIthitheP0nDie/j/k3HVMPodithNkZg4MOrZrBVVi0+C37VXEjjJFyIES7lk3DwHsc44puNbq9iXK1IsrEqGEWtLns4GdTI2EZoesXiILfCAlqoCl9m7V+//mAXOKhGImaTHeCXod2k8Iua73liOuErvxTZYZCQ= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1782446797; c=relaxed/simple; bh=rEMshQHon41Sg38Z8NXkpcWJh3M8Bi896t94h433fu4=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=Ig6SHCleYlEWtqIFm6QZT911UMpt1XykWYt90M6d2ZRu1GBF899xNO8tozzafWwhKmdz6IwbciK0rU4GS+2SBlmHoMMy0XhubqblW9K3lf4qNUCwLRD3RUCmxgkvBauVzFl6W6uaUpUuoXmYT44VVf/4dodi0Rpd0DaN9YPYr6o= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com; spf=pass smtp.mailfrom=arm.com; dkim=pass (1024-bit key) header.d=arm.com header.i=@arm.com header.b=Fj8zaU+K; arc=none smtp.client-ip=217.140.110.172 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=arm.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=arm.com header.i=@arm.com header.b="Fj8zaU+K" Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 5B59C2309; Thu, 25 Jun 2026 21:06:30 -0700 (PDT) Received: from [10.164.148.34] (MacBook-Pro.blr.arm.com [10.164.148.34]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id DFB573F905; Thu, 25 Jun 2026 21:06:24 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=simple/simple; d=arm.com; s=foss; t=1782446794; bh=rEMshQHon41Sg38Z8NXkpcWJh3M8Bi896t94h433fu4=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=Fj8zaU+KPHJaPRvKjc/hx7/6ra0teS9xSYnQ+26ogUvddNXmmNlv7QhKU25xMSAlN Wq2zLYewpTt7pliGi/d2ekpdihLOYB0/51RInxgvGHjGx+Vzf7VubYlS9fDgcfpi4B nV2D7k10xIHvTUErKhQKj/rkOvgkEaAxZJPyvZTg= Message-ID: <117fed1e-971d-4e31-a358-7a03f3db8338@arm.com> Date: Fri, 26 Jun 2026 09:36:21 +0530 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: Lance Yang Cc: muchun.song@linux.dev, osalvador@suse.de, akpm@linux-foundation.org, ljs@kernel.org, david@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: <20260625112955.3254283-5-dev.jain@arm.com> <20260626023127.60788-1-lance.yang@linux.dev> Content-Language: en-US From: Dev Jain In-Reply-To: <20260626023127.60788-1-lance.yang@linux.dev> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 26/06/26 8:01 am, Lance Yang wrote: > > On Thu, Jun 25, 2026 at 11:29:53AM +0000, Dev Jain wrote: >> check_pte() is the final validation step in page_vma_mapped_walk(). >> It reads pvmw->pte with ptep_get() to decide whether the entry maps >> the PFN range being walked. For hugetlb VMAs, that pointer refers >> to a hugetlb entry. >> >> On arches which provide their own huge_ptep_get() to dereference a huge >> pte pointer, accessing via ptep_get() would cause pte_pfn(), >> pte_present() etc to misbehave. >> >> It is not clear whether this has a trivially visible effect to userspace. >> >> Use huge_ptep_get() to dereference a huge pte pointer. >> >> Fixes: ace71a19cec5 ("mm: introduce page_vma_mapped_walk()") >> Cc: stable@vger.kernel.org >> Signed-off-by: Dev Jain >> --- >> mm/page_vma_mapped.c | 8 +++++++- >> 1 file changed, 7 insertions(+), 1 deletion(-) >> >> diff --git a/mm/page_vma_mapped.c b/mm/page_vma_mapped.c >> index 2ccbabfb2cc17..18e1d341f463c 100644 >> --- a/mm/page_vma_mapped.c >> +++ b/mm/page_vma_mapped.c >> @@ -107,7 +107,13 @@ static bool map_pte(struct page_vma_mapped_walk *pvmw, pmd_t *pmdvalp, >> static bool check_pte(struct page_vma_mapped_walk *pvmw, unsigned long pte_nr) > > Just one ordering thing: should this patch come first? > > Patches #01-#03 only reach the new huge_ptep_get() after > page_vma_mapped_walk() succeeds. But before this patch, hugetlb sill > goes through check_pte() (still using ptep_get()). You are right, but do we care? This is not a series meant for adding functionality. I just sent it as a series because they are similar fixes - the patches are to be applied individually with no dependency. > >> { >> unsigned long pfn; >> - pte_t ptent = ptep_get(pvmw->pte); >> + pte_t ptent; >> + >> + if (is_vm_hugetlb_page(pvmw->vma)) >> + ptent = huge_ptep_get(pvmw->vma->vm_mm, pvmw->address, >> + pvmw->pte); >> + else >> + ptent = ptep_get(pvmw->pte); >> >> if (pvmw->flags & PVMW_MIGRATION) { >> const softleaf_t entry = softleaf_from_pte(ptent); >> -- >> 2.43.0 >> >> >