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[79.179.85.180]) by smtp.gmail.com with ESMTPSA id h8sm17044762qtm.51.2020.01.20.04.03.22 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 20 Jan 2020 04:03:26 -0800 (PST) Date: Mon, 20 Jan 2020 07:03:20 -0500 From: "Michael S. Tsirkin" To: Stefano Garzarella Cc: David Miller , netdev@vger.kernel.org, linux-kernel@vger.kernel.org, jhansen@vmware.com, jasowang@redhat.com, kvm@vger.kernel.org, stefanha@redhat.com, virtualization@lists.linux-foundation.org, linux-hyperv@vger.kernel.org, decui@microsoft.com Subject: Re: [PATCH net-next 1/3] vsock: add network namespace support Message-ID: <20200120060601-mutt-send-email-mst@kernel.org> References: <20200116172428.311437-1-sgarzare@redhat.com> <20200116172428.311437-2-sgarzare@redhat.com> <20200120.100610.546818167633238909.davem@davemloft.net> <20200120101735.uyh4o64gb4njakw5@steredhat> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200120101735.uyh4o64gb4njakw5@steredhat> Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Jan 20, 2020 at 11:17:35AM +0100, Stefano Garzarella wrote: > On Mon, Jan 20, 2020 at 10:06:10AM +0100, David Miller wrote: > > From: Stefano Garzarella > > Date: Thu, 16 Jan 2020 18:24:26 +0100 > > > > > This patch adds 'netns' module param to enable this new feature > > > (disabled by default), because it changes vsock's behavior with > > > network namespaces and could break existing applications. > > > > Sorry, no. > > > > I wonder if you can even design a legitimate, reasonable, use case > > where these netns changes could break things. > > I forgot to mention the use case. > I tried the RFC with Kata containers and we found that Kata shim-v1 > doesn't work (Kata shim-v2 works as is) because there are the following > processes involved: > - kata-runtime (runs in the init_netns) opens /dev/vhost-vsock and > passes it to qemu > - kata-shim (runs in a container) wants to talk with the guest but the > vsock device is assigned to the init_netns and kata-shim runs in a > different netns, so the communication is not allowed > But, as you said, this could be a wrong design, indeed they already > found a fix, but I was not sure if others could have the same issue. > > In this case, do you think it is acceptable to make this change in > the vsock's behavior with netns and ask the user to change the design? David's question is what would be a usecase that's broken (as opposed to fixed) by enabling this by default. If it does exist, you need a way for userspace to opt-in, module parameter isn't that. > > > > > I am totally against adding a module parameter for this, it's > > incredibly confusing for users and will create a test scenerio > > that is strongly less likely to be covered. > > > > Got it, I'll remove the module parameter! > > Thanks, > Stefano