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[79.176.41.183]) by smtp.gmail.com with ESMTPSA id c45sm14187780qtd.43.2020.02.05.05.14.48 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 05 Feb 2020 05:14:52 -0800 (PST) Date: Wed, 5 Feb 2020 08:14:46 -0500 From: "Michael S. Tsirkin" To: Jason Gunthorpe Cc: Jason Wang , Shahaf Shuler , Tiwei Bie , "linux-kernel@vger.kernel.org" , "kvm@vger.kernel.org" , "virtualization@lists.linux-foundation.org" , "netdev@vger.kernel.org" , "rob.miller@broadcom.com" , "haotian.wang@sifive.com" , "eperezma@redhat.com" , "lulu@redhat.com" , Parav Pandit , "rdunlap@infradead.org" , "hch@infradead.org" , Jiri Pirko , "hanand@xilinx.com" , "mhabets@solarflare.com" , "maxime.coquelin@redhat.com" , "lingshan.zhu@intel.com" , "dan.daly@intel.com" , "cunming.liang@intel.com" , "zhihong.wang@intel.com" Subject: Re: [PATCH] vhost: introduce vDPA based backend Message-ID: <20200205081210-mutt-send-email-mst@kernel.org> References: <20200131033651.103534-1-tiwei.bie@intel.com> <7aab2892-bb19-a06a-a6d3-9c28bc4c3400@redhat.com> <20200205020247.GA368700@___> <112858a4-1a01-f4d7-e41a-1afaaa1cad45@redhat.com> <20200205125648.GV23346@mellanox.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200205125648.GV23346@mellanox.com> Sender: netdev-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org On Wed, Feb 05, 2020 at 08:56:48AM -0400, Jason Gunthorpe wrote: > On Wed, Feb 05, 2020 at 03:50:14PM +0800, Jason Wang wrote: > > > Would it be better for the map/umnap logic to happen inside each device ? > > > Devices that needs the IOMMU will call iommu APIs from inside the driver callback. > > > > Technically, this can work. But if it can be done by vhost-vpda it will make > > the vDPA driver more compact and easier to be implemented. > > Generally speaking, in the kernel, it is normal to not hoist code of > out drivers into subsystems until 2-3 drivers are duplicating that > code. It helps ensure the right design is used > > Jason That's up to the sybsystem maintainer really, as there's also some intuition involved in guessing a specific API is widely useful. In-kernel APIs are flexible, if we find something isn't needed we just drop it. -- MST