From patchwork Sun Mar 21 18:45:29 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Patchwork-Submitter: =?utf-8?q?Thomas_Hellstr=C3=B6m_=28Intel=29?= X-Patchwork-Id: 12153237 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-16.6 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_GIT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id B938BC433E1 for ; Sun, 21 Mar 2021 18:46:19 +0000 (UTC) Received: from gabe.freedesktop.org (gabe.freedesktop.org [131.252.210.177]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 7D6006195B for ; Sun, 21 Mar 2021 18:46:19 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 7D6006195B Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=shipmail.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=dri-devel-bounces@lists.freedesktop.org Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id 69B7C89FED; Sun, 21 Mar 2021 18:46:16 +0000 (UTC) Received: from pio-pvt-msa1.bahnhof.se (pio-pvt-msa1.bahnhof.se [79.136.2.40]) by gabe.freedesktop.org (Postfix) with ESMTPS id EFF6C89FEC for ; Sun, 21 Mar 2021 18:46:13 +0000 (UTC) Received: from localhost (localhost [127.0.0.1]) by pio-pvt-msa1.bahnhof.se (Postfix) with ESMTP id 470BD40762; Sun, 21 Mar 2021 19:46:12 +0100 (CET) Authentication-Results: pio-pvt-msa1.bahnhof.se; dkim=pass (1024-bit key; unprotected) header.d=shipmail.org header.i=@shipmail.org header.b="QgstfKZg"; dkim-atps=neutral X-Virus-Scanned: Debian amavisd-new at bahnhof.se Received: from pio-pvt-msa1.bahnhof.se ([127.0.0.1]) by localhost (pio-pvt-msa1.bahnhof.se [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id Zz_OBa3Q9uRF; Sun, 21 Mar 2021 19:46:10 +0100 (CET) Received: by pio-pvt-msa1.bahnhof.se (Postfix) with ESMTPA id C1E1F40391; Sun, 21 Mar 2021 19:46:09 +0100 (CET) Received: from localhost.localdomain (2.70.38.73.mobile.tre.se [2.70.38.73]) by mail1.shipmail.org (Postfix) with ESMTPSA id 08C20361E92; Sun, 21 Mar 2021 19:46:08 +0100 (CET) DKIM-Signature: v=1; a=rsa-sha256; c=simple/simple; d=shipmail.org; s=mail; t=1616352369; bh=ZnblYh+CL4ivnDI/E6ELj+Eqjfd3BvnVp2d0Kcr13LY=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=QgstfKZge72BS3EhP/IMO2NO6UDPjjWw3EOjZQCCAMAZbOhSTAWCUxhA0NuKRdbAb O17orFTuvm1/2qUmi4x93pHCMDBI9J8h4+MyhcJS2AMr2K+PHTWIkcqJyU4cmkLUCi R2rjarNFky6QOoSe+ndSkv2nZu4fJR5yy1qRp8gY= From: =?utf-8?q?Thomas_Hellstr=C3=B6m_=28Intel=29?= To: dri-devel@lists.freedesktop.org Subject: [RFC PATCH 2/2] mm,drm/ttm: Use VM_PFNMAP for TTM vmas Date: Sun, 21 Mar 2021 19:45:29 +0100 Message-Id: <20210321184529.59006-3-thomas_os@shipmail.org> X-Mailer: git-send-email 2.30.2 In-Reply-To: <20210321184529.59006-1-thomas_os@shipmail.org> References: <20210321184529.59006-1-thomas_os@shipmail.org> MIME-Version: 1.0 X-BeenThere: dri-devel@lists.freedesktop.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Direct Rendering Infrastructure - Development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Jason Gunthorpe , David Airlie , =?utf-8?q?Thomas_Hellstr=C3=B6m_=28Intel=29?= , linux-kernel@vger.kernel.org, linux-mm@kvack.org, Andrew Morton , Christian Koenig Errors-To: dri-devel-bounces@lists.freedesktop.org Sender: "dri-devel" To block fast gup we need to make sure TTM ptes are always special. With MIXEDMAP we, on architectures that don't support pte_special, insert normal ptes, but OTOH on those architectures, fast is not supported. At the same time, the function documentation to vm_normal_page() suggests that ptes pointing to system memory pages of MIXEDMAP vmas are always normal, but that doesn't seem consistent with what's implemented in vmf_insert_mixed(). I'm thus not entirely sure this patch is actually needed. But to make sure and to avoid also normal (non-fast) gup, make all TTM vmas PFNMAP. With PFNMAP we can't allow COW mappings anymore so make is_cow_mapping() available and use it to reject COW mappigs at mmap time. There was previously a comment in the code that WC mappings together with x86 PAT + PFNMAP was bad for performance. However from looking at vmf_insert_mixed() it looks like in the current code PFNMAP and MIXEDMAP are handled the same for architectures that support pte_special. This means there should not be a performance difference anymore, but this needs to be verified. Cc: Christian Koenig Cc: David Airlie Cc: Daniel Vetter Cc: Andrew Morton Cc: Jason Gunthorpe Cc: linux-mm@kvack.org Cc: dri-devel@lists.freedesktop.org Cc: linux-kernel@vger.kernel.org Signed-off-by: Thomas Hellström (Intel) Reviewed-by: Daniel Vetter --- drivers/gpu/drm/ttm/ttm_bo_vm.c | 22 ++++++++-------------- include/linux/mm.h | 5 +++++ mm/internal.h | 5 ----- 3 files changed, 13 insertions(+), 19 deletions(-) diff --git a/drivers/gpu/drm/ttm/ttm_bo_vm.c b/drivers/gpu/drm/ttm/ttm_bo_vm.c index 1c34983480e5..708c6fb9be81 100644 --- a/drivers/gpu/drm/ttm/ttm_bo_vm.c +++ b/drivers/gpu/drm/ttm/ttm_bo_vm.c @@ -372,12 +372,7 @@ vm_fault_t ttm_bo_vm_fault_reserved(struct vm_fault *vmf, * at arbitrary times while the data is mmap'ed. * See vmf_insert_mixed_prot() for a discussion. */ - if (vma->vm_flags & VM_MIXEDMAP) - ret = vmf_insert_mixed_prot(vma, address, - __pfn_to_pfn_t(pfn, PFN_DEV), - prot); - else - ret = vmf_insert_pfn_prot(vma, address, pfn, prot); + ret = vmf_insert_pfn_prot(vma, address, pfn, prot); /* Never error on prefaulted PTEs */ if (unlikely((ret & VM_FAULT_ERROR))) { @@ -555,18 +550,14 @@ static void ttm_bo_mmap_vma_setup(struct ttm_buffer_object *bo, struct vm_area_s * Note: We're transferring the bo reference to * vma->vm_private_data here. */ - vma->vm_private_data = bo; /* - * We'd like to use VM_PFNMAP on shared mappings, where - * (vma->vm_flags & VM_SHARED) != 0, for performance reasons, - * but for some reason VM_PFNMAP + x86 PAT + write-combine is very - * bad for performance. Until that has been sorted out, use - * VM_MIXEDMAP on all mappings. See freedesktop.org bug #75719 + * PFNMAP forces us to block COW mappings in mmap(), + * and with MIXEDMAP we would incorrectly allow fast gup + * on TTM memory on architectures that don't have pte_special. */ - vma->vm_flags |= VM_MIXEDMAP; - vma->vm_flags |= VM_IO | VM_DONTEXPAND | VM_DONTDUMP; + vma->vm_flags |= VM_PFNMAP | VM_IO | VM_DONTEXPAND | VM_DONTDUMP; } int ttm_bo_mmap(struct file *filp, struct vm_area_struct *vma, @@ -579,6 +570,9 @@ int ttm_bo_mmap(struct file *filp, struct vm_area_struct *vma, if (unlikely(vma->vm_pgoff < DRM_FILE_PAGE_OFFSET_START)) return -EINVAL; + if (unlikely(is_cow_mapping(vma->vm_flags))) + return -EINVAL; + bo = ttm_bo_vm_lookup(bdev, vma->vm_pgoff, vma_pages(vma)); if (unlikely(!bo)) return -EINVAL; diff --git a/include/linux/mm.h b/include/linux/mm.h index 77e64e3eac80..c6ebf7f9ddbb 100644 --- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -686,6 +686,11 @@ static inline bool vma_is_accessible(struct vm_area_struct *vma) return vma->vm_flags & VM_ACCESS_FLAGS; } +static inline bool is_cow_mapping(vm_flags_t flags) +{ + return (flags & (VM_SHARED | VM_MAYWRITE)) == VM_MAYWRITE; +} + #ifdef CONFIG_SHMEM /* * The vma_is_shmem is not inline because it is used only by slow diff --git a/mm/internal.h b/mm/internal.h index 9902648f2206..1432feec62df 100644 --- a/mm/internal.h +++ b/mm/internal.h @@ -296,11 +296,6 @@ static inline unsigned int buddy_order(struct page *page) */ #define buddy_order_unsafe(page) READ_ONCE(page_private(page)) -static inline bool is_cow_mapping(vm_flags_t flags) -{ - return (flags & (VM_SHARED | VM_MAYWRITE)) == VM_MAYWRITE; -} - /* * These three helpers classifies VMAs for virtual memory accounting. */