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Received: from foss.arm.com ([217.140.110.172]) by desiato.infradead.org with esmtp (Exim 4.99.2 #2 (Red Hat Linux)) id 1wjILS-0000000BlXI-0xe2 for linux-arm-kernel@lists.infradead.org; Mon, 13 Jul 2026 15:13:25 +0000 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 569451576; Mon, 13 Jul 2026 08:13:16 -0700 (PDT) Received: from [10.164.19.52] (unknown [10.164.19.52]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id B8B5B3F93E; Mon, 13 Jul 2026 08:13:16 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=simple/simple; d=arm.com; s=foss; t=1783955600; bh=FxZLR9R+Tw/RTXShqH2JiucTcF7BYOfeeQ7iY565rBc=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=l18hC4xT/sUPl8dCaDqcr/Ljf4Uj9z5GidEBxYlDB+Za59H+9rQjYDbLJFszRBqYW PxjxqhsMi5uQxLcE4Nl/DuuoVFXXxhLjquX1Os0uGlFuFAuY9NJJW5nS3LunIq6U9n qnX+Oi/SN60p8p0hOGnN7SN2AjE0Cqe1N/bsuZak= Message-ID: <54434a84-51b3-4e3f-988b-6bcbac5a2f42@arm.com> Date: Mon, 13 Jul 2026 20:43:14 +0530 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v6 0/6] mm/vmalloc: Speed up ioremap, vmalloc and vmap with contiguous memory To: Wen Jiang , Andrew Morton Cc: catalin.marinas@arm.com, linux-mm@kvack.org, urezki@gmail.com, will@kernel.org, Xueyuan.chen21@gmail.com, ajd@linux.ibm.com, anshuman.khandual@arm.com, david@kernel.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, rppt@kernel.org, ryan.roberts@arm.com, Wen Jiang References: <20260709073823.6643-1-jiangwen6@xiaomi.com> <20260709160805.26e63bae89dd03cf2951104e@linux-foundation.org> Content-Language: en-US From: Dev Jain In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.9.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20260713_161322_618914_975EF345 X-CRM114-Status: GOOD ( 21.59 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On 10/07/26 2:24 pm, Wen Jiang wrote: > On Fri, 10 Jul 2026 at 07:08, Andrew Morton wrote: >> >> On Thu, 9 Jul 2026 15:38:17 +0800 Wen Jiang wrote: >> >>> This patchset accelerates ioremap, vmalloc, and vmap when the memory >>> is physically fully or partially contiguous. >> >> Thanks, I added this to mm.git's mm-new branch for wider testing. >> >> AI review asked some questions, and some of them are new since the v5 >> series: >> https://sashiko.dev/#/patchset/20260709073823.6643-1-jiangwen6@xiaomi.com > > Hi Andrew, > > I've gone through the Sashiko findings: > > - Patch 1 (find_num_contig): Over-interpretation. No new hugetlbfs hstate > is added. The extra sizes are only used by init_mm kernel mappings via. > > - Patch 5/6 (NULL page): Invalid input. vmap() expects a fully populated > array of valid struct page pointers. Correct, but vmap_pages_pte_range has !page and !pfn_valid checks. I really hate those checks - if those checks have any remote possibility of firing, then we already have a bug at vm_map_ram -> vmap_pages_range -> vmap_pages_range_noflush -> kmsan_vmap_pages_range_noflush because the last function dereferences the struct page pointers. It is painful to do the page array sanity check deep into vmap - it implies we simply cannot play with the page array before that. But since vmap is an exported function, doing a sanity check for the page array in the vmap code makes sense. So how about the following: diff --git a/mm/vmalloc.c b/mm/vmalloc.c index afaa14ebf17bb..0c44bb7a45b5d 100644 --- a/mm/vmalloc.c +++ b/mm/vmalloc.c @@ -566,14 +566,6 @@ static int vmap_pages_pte_range(pmd_t *pmd, unsigned long addr, err = -EBUSY; break; } - if (WARN_ON(!page)) { - err = -ENOMEM; - break; - } - if (WARN_ON(!pfn_valid(page_to_pfn(page)))) { - err = -EINVAL; - break; - } pfn = page_to_pfn(page); size = vmap_set_ptes(pte, addr, end, pfn, prot, shift); @@ -603,11 +595,6 @@ static int vmap_pages_pmd_range(pud_t *pud, unsigned long addr, struct page *page = pages[*nr]; phys_addr_t phys_addr; - if (WARN_ON(!page)) - return -ENOMEM; - if (WARN_ON(!pfn_valid(page_to_pfn(page)))) - return -EINVAL; - phys_addr = page_to_phys(page); if (vmap_try_huge_pmd(pmd, addr, next, phys_addr, prot, @@ -3663,6 +3650,19 @@ static struct vm_struct *vmap_get_aligned_vm_area(unsigned long size, return __get_vm_area_node_aligned_caller(size, PAGE_SIZE, flags, caller); } +static inline bool vmap_page_sanity_checks(struct page **pages, unsigned int count) +{ + for (int i = 0; i < count; ++i) { + if (WARN_ON(!pages[i])) + return true; + + if (WARN_ON(!pfn_valid(page_to_pfn(pages[i])))) + return true; + } + + return false; +} + /** * vmap - map an array of pages into virtually contiguous space * @pages: array of page pointers @@ -3706,6 +3706,9 @@ void *vmap(struct page **pages, unsigned int count, if (!area) return NULL; + if (unlikely(vmap_page_sanity_checks(pages, count))) + return NULL; + addr = (unsigned long)area->addr; if (vmap_pages_range_batched(addr, addr + size, pgprot_nx(prot), pages) < 0) { Reasoning for calling vmap_page_sanity_checks() before vmap_pages_range_batched, and not at the start of vmap: I am worried that since vmap() is already very fast, we may cause a regression: vmap() -> scan page array with linear map pointers -> vmap_get_aligned_vm_area (does memory allocation, throwing out the linear map VAs from cache and TLB) -> walk the pgtables and again access cold page array. Perhaps I am being very pedantic here. What do you think? > > - Patch 6 (32-bit count << PAGE_SHIFT overflow): Pre-existing. This was > already discussed in the V3 thread, and a separate fix was proposed > there. > > Thanks, > Wen >