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Wed, 09 Jul 2025 10:55:49 -0700 (PDT) X-Google-Smtp-Source: AGHT+IF6EpX3Sw0s8jIsdyBPDf75ZN/LNVdeWPNO6Sp49Va5PEtvpZm4D60pPRoM6/TinkXfgx7S2Q== X-Received: by 2002:a05:622a:230b:b0:4a4:2fd6:90b7 with SMTP id d75a77b69052e-4a9e9cd8589mr5732521cf.17.1752083748545; Wed, 09 Jul 2025 10:55:48 -0700 (PDT) Received: from [192.168.40.164] ([70.105.235.240]) by smtp.gmail.com with ESMTPSA id d75a77b69052e-4a995841539sm98077701cf.53.2025.07.09.10.55.47 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 09 Jul 2025 10:55:48 -0700 (PDT) Message-ID: <01584206-e2c0-4881-aaf5-d6c552a30873@redhat.com> Date: Wed, 9 Jul 2025 13:55:46 -0400 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v3 02/20] hw/pci: Introduce pci_device_get_viommu_cap() Content-Language: en-US To: Nicolin Chen , Zhenzhong Duan Cc: qemu-devel@nongnu.org, alex.williamson@redhat.com, clg@redhat.com, eric.auger@redhat.com, mst@redhat.com, jasowang@redhat.com, peterx@redhat.com, jgg@nvidia.com, shameerali.kolothum.thodi@huawei.com, joao.m.martins@oracle.com, clement.mathieu--drif@eviden.com, kevin.tian@intel.com, yi.l.liu@intel.com, chao.p.peng@intel.com References: <20250708110601.633308-1-zhenzhong.duan@intel.com> <20250708110601.633308-3-zhenzhong.duan@intel.com> From: Donald Dutile In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Received-SPF: pass client-ip=170.10.129.124; envelope-from=ddutile@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.001, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H5=0.001, RCVD_IN_MSPIKE_WL=0.001, RCVD_IN_VALIDITY_RPBL_BLOCKED=0.001, RCVD_IN_VALIDITY_SAFE_BLOCKED=0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org On 7/8/25 8:39 PM, Nicolin Chen wrote: > On Tue, Jul 08, 2025 at 07:05:43AM -0400, Zhenzhong Duan wrote: >> diff --git a/include/hw/iommu.h b/include/hw/iommu.h >> new file mode 100644 >> index 0000000000..e80aaf4431 >> --- /dev/null >> +++ b/include/hw/iommu.h >> @@ -0,0 +1,16 @@ >> +/* >> + * General vIOMMU capabilities, flags, etc >> + * >> + * Copyright (C) 2025 Intel Corporation. >> + * >> + * SPDX-License-Identifier: GPL-2.0-or-later >> + */ >> + >> +#ifndef HW_IOMMU_H >> +#define HW_IOMMU_H >> + >> +enum { >> + VIOMMU_CAP_STAGE1 = BIT_ULL(0), /* stage1 page table supported */ >> +}; > > Thanks for this work. I am happy to see that we can share the > common code that allocates a NESTING_PARENT in the core using > this flag. > > Yet on ARM, a STAGE1 page table isn't always a nested S1, the > hardware accelerated one. More often, it can be just a regular > 1-stage translation table via emulated translation code and an > emulated iotlb. > Because the user-created smmuv3 started as 'accelerated smmuv3', and had been 'de-accelerated' to simply 'user created smmuv3', I'm looking for some clarification in the above statement/request. Is the above suppose to reflect that a nested IOMMU has some hw-acceleration in its Stage1 implementation? If so, then call it that: STAGE1_ACCEL. If it's suppose to represent that an IOMMU has nested/2-stage support, then the above is a valid cap; -but-, having a nested/2-stage support IOMMU doesn't necessarily mean its accelerated. So, let's ensure terminology, esp. bit-macro names(pace) reflects the (exact) meaning, and not any indirect meaning. A recent kvm-arm email thread had such indirect naming cleaned up when referring to pfn-map/device-map/struct-page-mapped pages, which I'd like not to start down a similar mis-naming/indirect-naming path here. Look forward to the clarification. - Don > I think this flag should indicate that the vIOMMU supports a > HW-accelerated nested S1 HWPT allocation/invalidation. > > So, perhaps: > /* hardware-accelerated nested stage-1 page table support */ > VIOMMU_CAP_NESTED_S1 = BIT_ULL(0), > ? > > Nicolin >