From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 14FAC1534E1 for ; Tue, 2 Jul 2024 12:34:35 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1719923676; cv=none; b=VJp4C6urEoZAytV56DqlNQthcgqLTouBk1A2xnhd1m6zI1YbtSmaqY6MwZP08IJ6AiVpca/xpsVdwoTQmV53AEhp3HQCmnS/cvL4dfqPyfQWMz8ojeN8sGma/7+4yYYw0Xy8dLckr50ix6imHjMxmL5wa/f74yXjmRHFtbtO2aA= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1719923676; c=relaxed/simple; bh=OH6oYUoymhgjC/JuHvWia2C/kOgOQMzd/Pdohajox5A=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=A2OijNCKvodBYaLlPxcl6nORWon9NNFCd4WHmFAI1RC6qDcA9C7TJm7Ts7zo5+T+PDK0QlA6wyHyV3qO1O36xwY/a86TyCKOVJljd7q5AaWipP3/B3hz2RkqT3mKz4Oyv3s3qd8q5o6128+eUZBy9uzoFQg0lW6/6rjRps5MEIA= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 Received: by smtp.kernel.org (Postfix) with ESMTPSA id 218CCC116B1; Tue, 2 Jul 2024 12:34:33 +0000 (UTC) Date: Tue, 2 Jul 2024 13:34:31 +0100 From: Catalin Marinas To: Yang Shi Cc: muchun.song@linux.dev, will@kernel.org, akpm@linux-foundation.org, linux-mm@kvack.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] hugetlbfs: add MTE support Message-ID: References: <20240625233717.2769975-1-yang@os.amperecomputing.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20240625233717.2769975-1-yang@os.amperecomputing.com> On Tue, Jun 25, 2024 at 04:37:17PM -0700, Yang Shi wrote: > MTE can be supported on ram based filesystem. It is supported on tmpfs. > There is use case to use MTE on hugetlbfs as well, adding MTE support. > > Signed-off-by: Yang Shi > --- > fs/hugetlbfs/inode.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/fs/hugetlbfs/inode.c b/fs/hugetlbfs/inode.c > index ecad73a4f713..c34faef62daf 100644 > --- a/fs/hugetlbfs/inode.c > +++ b/fs/hugetlbfs/inode.c > @@ -110,7 +110,7 @@ static int hugetlbfs_file_mmap(struct file *file, struct vm_area_struct *vma) > * way when do_mmap unwinds (may be important on powerpc > * and ia64). > */ > - vm_flags_set(vma, VM_HUGETLB | VM_DONTEXPAND); > + vm_flags_set(vma, VM_HUGETLB | VM_DONTEXPAND | VM_MTE_ALLOWED); > vma->vm_ops = &hugetlb_vm_ops; Last time I checked, about a year ago, this was not sufficient. One issue is that there's no arch_clear_hugetlb_flags() implemented by your patch, leaving PG_arch_{2,3} set on a page. The other issue was that I initially tried to do this only on the head page but this did not go well with the folio_copy() -> copy_highpage() which expects the PG_arch_* flags on each individual page. The alternative was for arch_clear_hugetlb_flags() to iterate over all the pages in a folio. I'd also like to see some tests added to tools/testing/selftest/arm64/mte to exercise MAP_HUGETLB with PROT_MTE: write/read tags, a series of mman+munmap (mostly to check if old page flags are still around), force some copy on write. I don't think we should merge the patch without proper tests. An untested hunk on top of your changes: diff --git a/arch/arm64/include/asm/hugetlb.h b/arch/arm64/include/asm/hugetlb.h index 3954cbd2ff56..5357b00b9087 100644 --- a/arch/arm64/include/asm/hugetlb.h +++ b/arch/arm64/include/asm/hugetlb.h @@ -20,7 +20,19 @@ extern bool arch_hugetlb_migration_supported(struct hstate *h); static inline void arch_clear_hugetlb_flags(struct folio *folio) { - clear_bit(PG_dcache_clean, &folio->flags); + unsigned long i, nr_pages = folio_nr_pages(folio); + const unsigned long clear_flags = BIT(PG_dcache_clean) | + BIT(PG_arch_2) | BIT(PG_arch_3); + + if (!system_supports_mte()) { + clear_bit(PG_dcache_clean, &folio->flags); + return; + } + + for (i = 0; i < nr_pages; i++) { + struct page *page = folio_page(folio, i); + page->flags &= ~clear_flags; + } } #define arch_clear_hugetlb_flags arch_clear_hugetlb_flags diff --git a/arch/arm64/include/asm/mman.h b/arch/arm64/include/asm/mman.h index 5966ee4a6154..304dfc499e68 100644 --- a/arch/arm64/include/asm/mman.h +++ b/arch/arm64/include/asm/mman.h @@ -28,7 +28,8 @@ static inline unsigned long arch_calc_vm_flag_bits(unsigned long flags) * backed by tags-capable memory. The vm_flags may be overridden by a * filesystem supporting MTE (RAM-based). */ - if (system_supports_mte() && (flags & MAP_ANONYMOUS)) + if (system_supports_mte() && + (flags & (MAP_ANONYMOUS | MAP_HUGETLB))) return VM_MTE_ALLOWED; return 0; -- Catalin