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([2404:f801:9000:1a:efea::50b]) by smtp.gmail.com with ESMTPSA id i26sm7738720pfu.6.2021.08.20.08.37.57 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 20 Aug 2021 08:38:11 -0700 (PDT) Subject: Re: [PATCH V3 13/13] HV/Storvsc: Add Isolation VM support for storvsc driver From: Tianyu Lan To: Michael Kelley , KY Srinivasan , Haiyang Zhang , Stephen Hemminger , "wei.liu@kernel.org" , Dexuan Cui , "tglx@linutronix.de" , "mingo@redhat.com" , "bp@alien8.de" , "x86@kernel.org" , "hpa@zytor.com" , "dave.hansen@linux.intel.com" , "luto@kernel.org" , "peterz@infradead.org" , "konrad.wilk@oracle.com" , "boris.ostrovsky@oracle.com" , "jgross@suse.com" , "sstabellini@kernel.org" , "joro@8bytes.org" , "will@kernel.org" , "davem@davemloft.net" , "kuba@kernel.org" , "jejb@linux.ibm.com" , "martin.petersen@oracle.com" , "arnd@arndb.de" , "hch@lst.de" , "m.szyprowski@samsung.com" , "robin.murphy@arm.com" , "thomas.lendacky@amd.com" , "brijesh.singh@amd.com" , "ardb@kernel.org" , Tianyu Lan , "pgonda@google.com" , "martin.b.radev@gmail.com" , "akpm@linux-foundation.org" , "kirill.shutemov@linux.intel.com" , "rppt@kernel.org" , "sfr@canb.auug.org.au" , "saravanand@fb.com" , "krish.sadhukhan@oracle.com" , "aneesh.kumar@linux.ibm.com" , "xen-devel@lists.xenproject.org" , "rientjes@google.com" , "hannes@cmpxchg.org" , "tj@kernel.org" Cc: "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 , "parri.andrea@gmail.com" , "dave.hansen@intel.com" References: <20210809175620.720923-1-ltykernel@gmail.com> <20210809175620.720923-14-ltykernel@gmail.com> Message-ID: <9ae704a9-838c-0a54-9c16-f0f10eaaaefe@gmail.com> Date: Fri, 20 Aug 2021 23:37:56 +0800 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:78.0) Gecko/20100101 Thunderbird/78.13.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org On 8/20/2021 11:20 PM, Tianyu Lan wrote: >> The whole approach here is to do dma remapping on each individual page >> of the I/O buffer.  But wouldn't it be possible to use dma_map_sg() to >> map >> each scatterlist entry as a unit?  Each scatterlist entry describes a >> range of >> physically contiguous memory.  After dma_map_sg(), the resulting dma >> address must also refer to a physically contiguous range in the swiotlb >> bounce buffer memory.   So at the top of the "for" loop over the >> scatterlist >> entries, do dma_map_sg() if we're in an isolated VM.  Then compute the >> hvpfn value based on the dma address instead of sg_page().  But >> everything >> else is the same, and the inner loop for populating the pfn_arry is >> unmodified. >> Furthermore, the dma_range array that you've added is not needed, since >> scatterlist entries already have a dma_address field for saving the >> mapped >> address, and dma_unmap_sg() uses that field. > > I don't use dma_map_sg() here in order to avoid introducing one more > loop(e,g dma_map_sg()). We already have a loop to populate > cmd_request->dma_range[] and so do the dma map in the same loop. Sorry for a typo. s/cmd_request->dma_range[]/payload->range.pfn_array[]/