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 X-Spam-Level: X-Spam-Status: No, score=-21.7 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,MENTIONS_GIT_HOSTING,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED, 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 0E33FC63697 for ; Thu, 19 Nov 2020 14:27:56 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id A860A238E6 for ; Thu, 19 Nov 2020 14:27:55 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727864AbgKSO1z (ORCPT ); Thu, 19 Nov 2020 09:27:55 -0500 Received: from foss.arm.com ([217.140.110.172]:58922 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727809AbgKSO1y (ORCPT ); Thu, 19 Nov 2020 09:27:54 -0500 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 7555D1042; Thu, 19 Nov 2020 06:27:53 -0800 (PST) Received: from entos-ampere-02.shanghai.arm.com (entos-ampere-02.shanghai.arm.com [10.169.214.110]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPA id 7E36E3F719; Thu, 19 Nov 2020 06:27:51 -0800 (PST) From: Jia He To: Alex Williamson , Cornelia Huck Cc: kvm@vger.kernel.org, linux-kernel@vger.kernel.org, Jia He Subject: [PATCH] vfio iommu type1: Bypass the vma permission check in vfio_pin_pages_remote() Date: Thu, 19 Nov 2020 22:27:37 +0800 Message-Id: <20201119142737.17574-1-justin.he@arm.com> X-Mailer: git-send-email 2.17.1 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org The permission of vfio iommu is different and incompatible with vma permission. If the iotlb->perm is IOMMU_NONE (e.g. qemu side), qemu will simply call unmap ioctl() instead of mapping. Hence vfio_dma_map() can't map a dma region with NONE permission. This corner case will be exposed in coming virtio_fs cache_size commit [1] - mmap(NULL, size, PROT_NONE, MAP_ANONYMOUS | MAP_PRIVATE, -1, 0); memory_region_init_ram_ptr() - re-mmap the above area with read/write authority. - vfio_dma_map() will be invoked when vfio device is hotplug added. qemu: vfio_listener_region_add() vfio_dma_map(..., readonly=false) map.flags is set to VFIO_DMA_MAP_FLAG_READ|VFIO_..._WRITE ioctl(VFIO_IOMMU_MAP_DMA) kernel: vfio_dma_do_map() vfio_pin_map_dma() vfio_pin_pages_remote() vaddr_get_pfn() ... check_vma_flags() failed! because vm_flags hasn't VM_WRITE && gup_flags has FOLL_WRITE It will report error in qemu log when hotplug adding(vfio) a nvme disk to qemu guest on an Ampere EMAG server: "VFIO_MAP_DMA failed: Bad address" [1] https://gitlab.com/virtio-fs/qemu/-/blob/virtio-fs-dev/hw/virtio/vhost-user-fs.c#L502 Signed-off-by: Jia He --- drivers/vfio/vfio_iommu_type1.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/drivers/vfio/vfio_iommu_type1.c b/drivers/vfio/vfio_iommu_type1.c index 67e827638995..33faa6b7dbd4 100644 --- a/drivers/vfio/vfio_iommu_type1.c +++ b/drivers/vfio/vfio_iommu_type1.c @@ -453,7 +453,8 @@ static int vaddr_get_pfn(struct mm_struct *mm, unsigned long vaddr, flags |= FOLL_WRITE; mmap_read_lock(mm); - ret = pin_user_pages_remote(mm, vaddr, 1, flags | FOLL_LONGTERM, + ret = pin_user_pages_remote(mm, vaddr, 1, + flags | FOLL_LONGTERM | FOLL_FORCE, page, NULL, NULL); if (ret == 1) { *pfn = page_to_pfn(page[0]); -- 2.17.1