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=-2.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=no 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 30BFCC76190 for ; Fri, 26 Jul 2019 02:22:17 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 0EA60217D4 for ; Fri, 26 Jul 2019 02:22:17 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726178AbfGZCWQ (ORCPT ); Thu, 25 Jul 2019 22:22:16 -0400 Received: from mga05.intel.com ([192.55.52.43]:47983 "EHLO mga05.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725808AbfGZCWP (ORCPT ); Thu, 25 Jul 2019 22:22:15 -0400 X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from orsmga002.jf.intel.com ([10.7.209.21]) by fmsmga105.fm.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 25 Jul 2019 19:22:15 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.64,308,1559545200"; d="scan'208";a="181729461" Received: from allen-box.sh.intel.com (HELO [10.239.159.136]) ([10.239.159.136]) by orsmga002.jf.intel.com with ESMTP; 25 Jul 2019 19:22:11 -0700 Cc: baolu.lu@linux.intel.com, David Woodhouse , Joerg Roedel , Bjorn Helgaas , ashok.raj@intel.com, jacob.jun.pan@intel.com, alan.cox@intel.com, kevin.tian@intel.com, mika.westerberg@linux.intel.com, Ingo Molnar , Greg Kroah-Hartman , pengfei.xu@intel.com, Konrad Rzeszutek Wilk , Marek Szyprowski , Robin Murphy , Jonathan Corbet , Boris Ostrovsky , Juergen Gross , Stefano Stabellini , Steven Rostedt , iommu@lists.linux-foundation.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v5 06/10] swiotlb: Zero out bounce buffer for untrusted device To: Christoph Hellwig References: <20190725031717.32317-1-baolu.lu@linux.intel.com> <20190725031717.32317-7-baolu.lu@linux.intel.com> <20190725114903.GB31065@lst.de> From: Lu Baolu Message-ID: Date: Fri, 26 Jul 2019 10:21:36 +0800 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.7.2 MIME-Version: 1.0 In-Reply-To: <20190725114903.GB31065@lst.de> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi, On 7/25/19 7:49 PM, Christoph Hellwig wrote: >> index 43c88626a1f3..edc84a00b9f9 100644 >> --- a/kernel/dma/swiotlb.c >> +++ b/kernel/dma/swiotlb.c >> @@ -35,6 +35,7 @@ >> #include >> #include >> #include >> +#include >> #ifdef CONFIG_DEBUG_FS >> #include >> #endif >> @@ -562,6 +563,11 @@ phys_addr_t swiotlb_tbl_map_single(struct device *hwdev, >> */ >> for (i = 0; i < nslots; i++) >> io_tlb_orig_addr[index+i] = orig_addr + (i << IO_TLB_SHIFT); >> + >> + /* Zero out the bounce buffer if the consumer is untrusted. */ >> + if (dev_is_untrusted(hwdev)) >> + memset(phys_to_virt(tlb_addr), 0, alloc_size); > > Hmm. Maybe we need to move the untrusted flag to struct device? > Directly poking into the pci_dev from swiotlb is a bit of a layering > violation. Yes. We can consider this. But I tend to think that it's worth of a separated series. That's a reason why I defined dev_is_untrusted(). This helper keeps the caller same when moving the untrusted flag. > >> + >> if (!(attrs & DMA_ATTR_SKIP_CPU_SYNC) && >> (dir == DMA_TO_DEVICE || dir == DMA_BIDIRECTIONAL)) >> swiotlb_bounce(orig_addr, tlb_addr, mapping_size, DMA_TO_DEVICE); > > Also for the case where we bounce here we only need to zero the padding > (if there is any), so I think we could optimize this a bit. > Yes. There's duplication here. Best regards, Baolu