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Thu, 16 Apr 2020 06:28:44 -0700 Received: from shsmsx151.ccr.corp.intel.com (10.239.6.50) by FMSMSX102.amr.corp.intel.com (10.18.124.200) with Microsoft SMTP Server (TLS) id 14.3.439.0; Thu, 16 Apr 2020 06:28:43 -0700 Received: from shsmsx104.ccr.corp.intel.com ([169.254.5.225]) by SHSMSX151.ccr.corp.intel.com ([169.254.3.22]) with mapi id 14.03.0439.000; Thu, 16 Apr 2020 21:28:41 +0800 From: "Tian, Kevin" To: Auger Eric , "Liu, Yi L" , "Alex Williamson" Subject: RE: [PATCH v1 7/8] vfio/type1: Add VFIO_IOMMU_CACHE_INVALIDATE Thread-Topic: [PATCH v1 7/8] vfio/type1: Add VFIO_IOMMU_CACHE_INVALIDATE Thread-Index: AQHWAEUdbUtKvEWiiEiZu1SnRvWegKhl0sQAgAEuFaCAABNDAIAUHAOAgACdTsD//4TxAIAAkflQ Date: Thu, 16 Apr 2020 13:28:41 +0000 Message-ID: References: <1584880325-10561-1-git-send-email-yi.l.liu@intel.com> <1584880325-10561-8-git-send-email-yi.l.liu@intel.com> <20200402142428.2901432e@w520.home> <20200403093436.094b1928@w520.home> <7d13bdbb-e972-c301-0970-90f63ecf69fc@redhat.com> In-Reply-To: <7d13bdbb-e972-c301-0970-90f63ecf69fc@redhat.com> Accept-Language: en-US Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: dlp-product: dlpe-windows dlp-version: 11.2.0.6 dlp-reaction: no-action x-originating-ip: [10.239.127.40] MIME-Version: 1.0 Cc: "jean-philippe@linaro.org" , "Raj, Ashok" , "kvm@vger.kernel.org" , "Tian, Jun J" , "iommu@lists.linux-foundation.org" , "linux-kernel@vger.kernel.org" , "Sun, Yi Y" , "Wu, Hao" X-BeenThere: iommu@lists.linux-foundation.org X-Mailman-Version: 2.1.15 Precedence: list List-Id: Development issues for Linux IOMMU support List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: iommu-bounces@lists.linux-foundation.org Sender: "iommu" > From: Auger Eric > Sent: Thursday, April 16, 2020 8:43 PM > > Hi Kevin, > On 4/16/20 2:09 PM, Tian, Kevin wrote: > >> From: Liu, Yi L > >> Sent: Thursday, April 16, 2020 6:40 PM > >> > >> Hi Alex, > >> Still have a direction question with you. Better get agreement with you > >> before heading forward. > >> > >>> From: Alex Williamson > >>> Sent: Friday, April 3, 2020 11:35 PM > >> [...] > >>>>>> + * > >>>>>> + * returns: 0 on success, -errno on failure. > >>>>>> + */ > >>>>>> +struct vfio_iommu_type1_cache_invalidate { > >>>>>> + __u32 argsz; > >>>>>> + __u32 flags; > >>>>>> + struct iommu_cache_invalidate_info cache_info; > >>>>>> +}; > >>>>>> +#define VFIO_IOMMU_CACHE_INVALIDATE _IO(VFIO_TYPE, > >>> VFIO_BASE > >>>>> + 24) > >>>>> > >>>>> The future extension capabilities of this ioctl worry me, I wonder if > >>>>> we should do another data[] with flag defining that data as > >> CACHE_INFO. > >>>> > >>>> Can you elaborate? Does it mean with this way we don't rely on iommu > >>>> driver to provide version_to_size conversion and instead we just pass > >>>> data[] to iommu driver for further audit? > >>> > >>> No, my concern is that this ioctl has a single function, strictly tied > >>> to the iommu uapi. If we replace cache_info with data[] then we can > >>> define a flag to specify that data[] is struct > >>> iommu_cache_invalidate_info, and if we need to, a different flag to > >>> identify data[] as something else. For example if we get stuck > >>> expanding cache_info to meet new demands and develop a new uapi to > >>> solve that, how would we expand this ioctl to support it rather than > >>> also create a new ioctl? There's also a trade-off in making the ioctl > >>> usage more difficult for the user. I'd still expect the vfio layer to > >>> check the flag and interpret data[] as indicated by the flag rather > >>> than just passing a blob of opaque data to the iommu layer though. > >>> Thanks, > >> > >> Based on your comments about defining a single ioctl and a unified > >> vfio structure (with a @data[] field) for pasid_alloc/free, bind/ > >> unbind_gpasid, cache_inv. After some offline trying, I think it would > >> be good for bind/unbind_gpasid and cache_inv as both of them use the > >> iommu uapi definition. While the pasid alloc/free operation doesn't. > >> It would be weird to put all of them together. So pasid alloc/free > >> may have a separate ioctl. It would look as below. Does this direction > >> look good per your opinion? > >> > >> ioctl #22: VFIO_IOMMU_PASID_REQUEST > >> /** > >> * @pasid: used to return the pasid alloc result when flags == > ALLOC_PASID > >> * specify a pasid to be freed when flags == FREE_PASID > >> * @range: specify the allocation range when flags == ALLOC_PASID > >> */ > >> struct vfio_iommu_pasid_request { > >> __u32 argsz; > >> #define VFIO_IOMMU_ALLOC_PASID (1 << 0) > >> #define VFIO_IOMMU_FREE_PASID (1 << 1) > >> __u32 flags; > >> __u32 pasid; > >> struct { > >> __u32 min; > >> __u32 max; > >> } range; > >> }; > >> > >> ioctl #23: VFIO_IOMMU_NESTING_OP > >> struct vfio_iommu_type1_nesting_op { > >> __u32 argsz; > >> __u32 flags; > >> __u32 op; > >> __u8 data[]; > >> }; > >> > >> /* Nesting Ops */ > >> #define VFIO_IOMMU_NESTING_OP_BIND_PGTBL 0 > >> #define VFIO_IOMMU_NESTING_OP_UNBIND_PGTBL 1 > >> #define VFIO_IOMMU_NESTING_OP_CACHE_INVLD 2 > >> > > > > Then why cannot we just put PASID into the header since the > > majority of nested usage is associated with a pasid? > > > > ioctl #23: VFIO_IOMMU_NESTING_OP > > struct vfio_iommu_type1_nesting_op { > > __u32 argsz; > > __u32 flags; > > __u32 op; > > __u32 pasid; > > __u8 data[]; > > }; > > > > In case of SMMUv2 which supports nested w/o PASID, this field can > > be ignored for that specific case. > On my side I would prefer keeping the pasid in the data[]. This is not > always used. > > For instance, in iommu_cache_invalidate_info/iommu_inv_pasid_info we > devised flags to tell whether the PASID is used. > But don't we include a PASID in both invalidate structures already? struct iommu_inv_addr_info { #define IOMMU_INV_ADDR_FLAGS_PASID (1 << 0) #define IOMMU_INV_ADDR_FLAGS_ARCHID (1 << 1) #define IOMMU_INV_ADDR_FLAGS_LEAF (1 << 2) __u32 flags; __u32 archid; __u64 pasid; __u64 addr; __u64 granule_size; __u64 nb_granules; }; struct iommu_inv_pasid_info { #define IOMMU_INV_PASID_FLAGS_PASID (1 << 0) #define IOMMU_INV_PASID_FLAGS_ARCHID (1 << 1) __u32 flags; __u32 archid; __u64 pasid; }; then consolidating the pasid field into generic header doesn't hurt. the specific handler still rely on flags to tell whether it is used? Thanks Kevin _______________________________________________ iommu mailing list iommu@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/iommu