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([2404:f801:9000:1a:efea::4b1]) by smtp.gmail.com with ESMTPSA id 1sm8338487pjm.8.2021.06.10.07.25.11 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 10 Jun 2021 07:25:23 -0700 (PDT) Subject: Re: [RFC PATCH V3 08/11] swiotlb: Add bounce buffer remap address setting function From: Tianyu Lan To: Christoph Hellwig Cc: kys@microsoft.com, haiyangz@microsoft.com, sthemmin@microsoft.com, wei.liu@kernel.org, decui@microsoft.com, tglx@linutronix.de, mingo@redhat.com, bp@alien8.de, x86@kernel.org, hpa@zytor.com, arnd@arndb.de, dave.hansen@linux.intel.com, luto@kernel.org, peterz@infradead.org, akpm@linux-foundation.org, kirill.shutemov@linux.intel.com, rppt@kernel.org, hannes@cmpxchg.org, cai@lca.pw, krish.sadhukhan@oracle.com, saravanand@fb.com, Tianyu.Lan@microsoft.com, konrad.wilk@oracle.com, m.szyprowski@samsung.com, robin.murphy@arm.com, boris.ostrovsky@oracle.com, jgross@suse.com, sstabellini@kernel.org, joro@8bytes.org, will@kernel.org, xen-devel@lists.xenproject.org, davem@davemloft.net, kuba@kernel.org, jejb@linux.ibm.com, martin.petersen@oracle.com, iommu@lists.linux-foundation.org, linux-arch@vger.kernel.org, linux-hyperv@vger.kernel.org, linux-kernel@vger.kernel.org, linux-scsi@vger.kernel.org, netdev@vger.kernel.org, vkuznets@redhat.com, thomas.lendacky@amd.com, brijesh.singh@amd.com, sunilmut@microsoft.com References: <20210530150628.2063957-1-ltykernel@gmail.com> <20210530150628.2063957-9-ltykernel@gmail.com> <20210607064312.GB24478@lst.de> <48516ce3-564c-419e-b355-0ce53794dcb1@gmail.com> Message-ID: <9c05f7fd-6460-5d4a-aa83-08626839d18e@gmail.com> Date: Thu, 10 Jun 2021 22:25:10 +0800 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:78.0) Gecko/20100101 Thunderbird/78.11.0 MIME-Version: 1.0 In-Reply-To: <48516ce3-564c-419e-b355-0ce53794dcb1@gmail.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-arch@vger.kernel.org On 6/7/2021 10:56 PM, Tianyu Lan wrote: > > On 6/7/2021 2:43 PM, Christoph Hellwig wrote: >> On Sun, May 30, 2021 at 11:06:25AM -0400, Tianyu Lan wrote: >>> From: Tianyu Lan >>> >>> For Hyper-V isolation VM with AMD SEV SNP, the bounce buffer(shared >>> memory) >>> needs to be accessed via extra address space(e.g address above bit39). >>> Hyper-V code may remap extra address space outside of swiotlb. swiotlb_ >>> bounce() needs to use remap virtual address to copy data from/to bounce >>> buffer. Add new interface swiotlb_set_bounce_remap() to do that. >> >> Why can't you use the bus_dma_region ranges to remap to your preferred >> address? >> > > Thanks for your suggestion. > > These addresses in extra address space works as system memory mirror. > The shared memory with host in Isolation VM needs to be accessed via > extra address space which is above shared gpa boundary. During > initializing swiotlb bounce buffer pool, only address bellow shared gpa > boundary can be accepted by swiotlb API because it is treated as system > memory and managed by memory management. This is why Hyper-V swiotlb > bounce buffer pool needs to be allocated in Hyper-V code and map > associated physical address in extra address space. The patch target is > to add the new interface to set start virtual address of bounce buffer > pool and let swiotlb boucne buffer copy function to use right virtual > address for extra address space. > > bus_dma_region is to translate cpu physical address to dma address. > It can't modify the virtual address of bounce buffer pool and let > swiotlb code to copy data with right address. If some thing missed, > please correct me. > Hi Christoph: Sorry to bother you. Could you have a look at my previous reply? I try figuring out the right way. Thanks.