From mboxrd@z Thu Jan 1 00:00:00 1970 From: Lu Baolu Subject: Re: [PATCH v1 4/9] iommu/vt-d: Add bounce buffer API for domain map/unmap Date: Tue, 19 Mar 2019 15:59:48 +0800 Message-ID: References: <20190312060005.12189-1-baolu.lu@linux.intel.com> <20190312060005.12189-5-baolu.lu@linux.intel.com> <20190312163845.GA13141@infradead.org> <20190313161029.GA23513@infradead.org> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20190313161029.GA23513@infradead.org> Content-Language: en-US Sender: linux-kernel-owner@vger.kernel.org To: Christoph Hellwig Cc: baolu.lu@linux.intel.com, David Woodhouse , Joerg Roedel , ashok.raj@intel.com, jacob.jun.pan@intel.com, alan.cox@intel.com, kevin.tian@intel.com, mika.westerberg@linux.intel.com, pengfei.xu@intel.com, iommu@lists.linux-foundation.org, linux-kernel@vger.kernel.org, Jacob Pan List-Id: iommu@lists.linux-foundation.org Hi Christoph, On 3/14/19 12:10 AM, Christoph Hellwig wrote: > On Wed, Mar 13, 2019 at 10:31:52AM +0800, Lu Baolu wrote: >> Hi again, >> >> On 3/13/19 10:04 AM, Lu Baolu wrote: >>> Hi, >>> >>> On 3/13/19 12:38 AM, Christoph Hellwig wrote: >>>> On Tue, Mar 12, 2019 at 02:00:00PM +0800, Lu Baolu wrote: >>>>> This adds the APIs for bounce buffer specified domain >>>>> map() and unmap(). The start and end partial pages will >>>>> be mapped with bounce buffered pages instead. This will >>>>> enhance the security of DMA buffer by isolating the DMA >>>>> attacks from malicious devices. >>>> >>>> Please reuse the swiotlb code instead of reinventing it. >>>> >> >> Just looked into the code again. At least we could reuse below >> functions: >> >> swiotlb_tbl_map_single() >> swiotlb_tbl_unmap_single() >> swiotlb_tbl_sync_single() >> >> Anything else? > > Yes, that is probably about the level you want to reuse, given that the > next higher layer already has hooks into the direct mapping code. > I am trying to change my code to reuse swiotlb. But I found that swiotlb might not be suitable for my case. Below is what I got with swiotlb_map(): phy_addr size tlb_addr -------------------------------- 0x167eec330 0x8 0x85dc6000 0x167eef5c0 0x40 0x85dc6800 0x167eec330 0x8 0x85dc7000 0x167eef5c0 0x40 0x85dc7800 But what I expected to get is: phy_addr size tlb_addr -------------------------------- 0x167eec330 0x8 0xAAAAA330 0x167eef5c0 0x40 0xBBBBB5c0 0x167eec330 0x8 0xCCCCC330 0x167eef5c0 0x40 0xDDDDD5c0 , where 0xXXXXXX000 is the physical address of a bounced page. Basically, I want a bounce page to replace a leaf page in the vt-d page table, which maps a buffer with size less than a PAGE_SIZE. Best regards, Lu Baolu