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[204.195.22.127]) by smtp.gmail.com with ESMTPSA id d24sm15022315pfq.75.2019.12.20.14.30.03 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 20 Dec 2019 14:30:04 -0800 (PST) Date: Fri, 20 Dec 2019 14:30:01 -0800 From: Stephen Hemminger To: David Miller Cc: cforno12@linux.vnet.ibm.com, netdev@vger.kernel.org, mst@redhat.com, jasowang@redhat.com, haiyangz@microsoft.com, sthemmin@microsoft.com, sashal@kernel.org, tlfalcon@linux.ibm.com Subject: Re: [PATCH, net-next, v3, 0/2] net/ethtool: Introduce link_ksettings API for virtual network devices Message-ID: <20191220143001.1e78dc82@hermes.lan> In-Reply-To: <20191219.141619.1840874136750249908.davem@davemloft.net> References: <20191219194057.4208-1-cforno12@linux.vnet.ibm.com> <20191219131156.21332555@hermes.lan> <20191219.141619.1840874136750249908.davem@davemloft.net> MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: netdev-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org On Thu, 19 Dec 2019 14:16:19 -0800 (PST) David Miller wrote: > From: Stephen Hemminger > Date: Thu, 19 Dec 2019 13:11:56 -0800 > > > I don't think this makes sense for netvsc. The speed and duplex have no > > meaning, why do you want to allow overriding it? If this is to try and make > > some dashboard look good; then you aren't seeing the real speed which is > > what only the host knows. Plus it does take into account the accelerated > > networking path. > > Maybe that's the point, userspace has extraneous knowledge it might > use to set it accurately. > > This helps for bonding/team etc. as well. > > I don't think there is any real harm in allowing to set this, and > we've done this in the past I think. Looked a little more. The netvsc driver does query the host already and get a correct link speed. See drivers/net/hyperv/rndis_filter.c If running on Windows Server 2019 you will see speed report of 40G if using 40G Mellanox SRIOV, and 10G if using a private virtual network. On Azure, the guest sees the speed of the underlying network connection which varies based on machine type. Bottom line: it behaves like real hardware now, why should we allow user to set it for netvsc and not other real hardware.