From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id CA20CC0015E for ; Mon, 3 Jul 2023 09:48:53 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231259AbjGCJsw (ORCPT ); Mon, 3 Jul 2023 05:48:52 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:48808 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229644AbjGCJsd (ORCPT ); Mon, 3 Jul 2023 05:48:33 -0400 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by lindbergh.monkeyblade.net (Postfix) with ESMTP id 80F4CDD for ; Mon, 3 Jul 2023 02:48:32 -0700 (PDT) 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 CF4EF1FB; Mon, 3 Jul 2023 02:49:14 -0700 (PDT) Received: from [10.57.76.103] (unknown [10.57.76.103]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 0970A3F762; Mon, 3 Jul 2023 02:48:28 -0700 (PDT) Message-ID: Date: Mon, 3 Jul 2023 10:48:27 +0100 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:102.0) Gecko/20100101 Thunderbird/102.12.0 Subject: Re: [PATCH v1 11/14] arm64/mm: Wire up PTE_CONT for user mappings To: John Hubbard , Catalin Marinas , Will Deacon , Ard Biesheuvel , Marc Zyngier , Oliver Upton , James Morse , Suzuki K Poulose , Zenghui Yu , Andrey Ryabinin , Alexander Potapenko , Andrey Konovalov , Dmitry Vyukov , Vincenzo Frascino , Andrew Morton , Anshuman Khandual , Matthew Wilcox , Yu Zhao , Mark Rutland Cc: linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org References: <20230622144210.2623299-1-ryan.roberts@arm.com> <20230622144210.2623299-12-ryan.roberts@arm.com> From: Ryan Roberts In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 30/06/2023 02:54, John Hubbard wrote: > On 6/22/23 07:42, Ryan Roberts wrote: >> With the ptep API sufficiently refactored, we can now introduce a new >> "contpte" API layer, which transparently manages the PTE_CONT bit for >> user mappings. Whenever it detects a set of PTEs that meet the >> requirements for a contiguous range, the PTEs are re-painted with the >> PTE_CONT bit. >> >> This initial change provides a baseline that can be optimized in future >> commits. That said, fold/unfold operations (which imply tlb >> invalidation) are avoided where possible with a few tricks for >> access/dirty bit management. >> >> Write-enable and write-protect modifications are likely non-optimal and >> likely incure a regression in fork() performance. This will be addressed >> separately. >> >> Signed-off-by: Ryan Roberts >> --- > > Hi Ryan! > > While trying out the full series from your gitlab features/granule_perf/all > branch, I found it necessary to EXPORT a symbol in order to build this. Thanks for the bug report! > Please see below: > > ... >> + >> +pte_t contpte_ptep_get(pte_t *ptep, pte_t orig_pte) >> +{ >> +    /* >> +     * Gather access/dirty bits, which may be populated in any of the ptes >> +     * of the contig range. We are guarranteed to be holding the PTL, so any >> +     * contiguous range cannot be unfolded or otherwise modified under our >> +     * feet. >> +     */ >> + >> +    pte_t pte; >> +    int i; >> + >> +    ptep = contpte_align_down(ptep); >> + >> +    for (i = 0; i < CONT_PTES; i++, ptep++) { >> +        pte = __ptep_get(ptep); >> + >> +        /* >> +         * Deal with the partial contpte_ptep_get_and_clear_full() case, >> +         * where some of the ptes in the range may be cleared but others >> +         * are still to do. See contpte_ptep_get_and_clear_full(). >> +         */ >> +        if (pte_val(pte) == 0) >> +            continue; >> + >> +        if (pte_dirty(pte)) >> +            orig_pte = pte_mkdirty(orig_pte); >> + >> +        if (pte_young(pte)) >> +            orig_pte = pte_mkyoung(orig_pte); >> +    } >> + >> +    return orig_pte; >> +} > > Here we need something like this, in order to get it to build in all > possible configurations: > > EXPORT_SYMBOL_GPL(contpte_ptep_get); > > (and a corresponding "#include linux/export.h" at the top of the file). > > Because, the static inline functions invoke this routine, above. A quick grep through the drivers directory shows: ptep_get() is used by: - drivers/gpu/drm/i915/gem/selftests/i915_gem_mman.c - drivers/misc/sgi-gru/grufault.c - drivers/vfio/vfio_iommu_type1.c - drivers/xen/privcmd.c ptep_set_at() is used by: - drivers/gpu/drm/i915/i915_mm.c - drivers/xen/xlate_mmu.c None of the other symbols are called, but I guess it is possible that out of tree modules are calling others. So on the basis that these symbols were previously pure inline, I propose to export all the contpte_* symbols using EXPORT_SYMBOL() so that anything that was previously calling them successfully continue to do so. Will include in v2. Thanks, Ryan > > thanks,