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([2404:f801:9000:1a:efea::50b]) by smtp.gmail.com with ESMTPSA id 19sm2945794pfw.203.2021.08.13.10.58.34 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 13 Aug 2021 10:58:47 -0700 (PDT) Subject: Re: [PATCH V3 10/13] x86/Swiotlb: Add Swiotlb bounce buffer remap function for HV IVM 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, 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, m.szyprowski@samsung.com, robin.murphy@arm.com, thomas.lendacky@amd.com, brijesh.singh@amd.com, ardb@kernel.org, Tianyu.Lan@microsoft.com, 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, michael.h.kelley@microsoft.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, parri.andrea@gmail.com, dave.hansen@intel.com References: <20210809175620.720923-1-ltykernel@gmail.com> <20210809175620.720923-11-ltykernel@gmail.com> <20210812122741.GC19050@lst.de> From: Tianyu Lan Message-ID: Date: Sat, 14 Aug 2021 01:58:32 +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: <20210812122741.GC19050@lst.de> 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-hyperv@vger.kernel.org On 8/12/2021 8:27 PM, Christoph Hellwig wrote: > This is still broken. You need to make sure the actual DMA allocations > do have struct page backing. > Hi Christoph: swiotlb_tbl_map_single() still returns PA below vTOM/share_gpa_ boundary. These PAs has backing pages and belong to system memory. In other word, all PAs passed to DMA API have backing pages and these is no difference between Isolation guest and traditional guest for DMA API. The new mapped VA for PA above vTOM here is just to access the bounce buffer in the swiotlb code and isn't exposed to outside.