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[79.180.2.31]) by smtp.gmail.com with ESMTPSA id e4sm11440644ejz.4.2021.02.28.13.30.10 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sun, 28 Feb 2021 13:30:11 -0800 (PST) Date: Sun, 28 Feb 2021 16:30:08 -0500 From: "Michael S. Tsirkin" To: Jason Wang Cc: Si-Wei Liu , elic@nvidia.com, linux-kernel@vger.kernel.org, virtualization@lists.linux-foundation.org, netdev@vger.kernel.org Subject: Re: [PATCH] vdpa/mlx5: set_features should allow reset to zero Message-ID: <20210228162909-mutt-send-email-mst@kernel.org> References: <20210223082536-mutt-send-email-mst@kernel.org> <3ff5fd23-1db0-2f95-4cf9-711ef403fb62@oracle.com> <20210224000057-mutt-send-email-mst@kernel.org> <0559fd8c-ff44-cb7a-8a74-71976dd2ee33@redhat.com> <20210224014232-mutt-send-email-mst@kernel.org> <20210224021222-mutt-send-email-mst@kernel.org> <20210224034240-mutt-send-email-mst@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Feb 24, 2021 at 05:30:37PM +0800, Jason Wang wrote: > > On 2021/2/24 4:43 下午, Michael S. Tsirkin wrote: > > On Wed, Feb 24, 2021 at 04:26:43PM +0800, Jason Wang wrote: > > > Basically on first guest access QEMU would tell kernel whether > > > guest is using the legacy or the modern interface. > > > E.g. virtio_pci_config_read/virtio_pci_config_write will call ioctl(ENABLE_LEGACY, 1) > > > while virtio_pci_common_read will call ioctl(ENABLE_LEGACY, 0) > > > > > > > > > But this trick work only for PCI I think? > > > > > > Thanks > > ccw has a revision it can check. mmio does not have transitional devices > > at all. > > > Ok, then we can do the workaround in the qemu, isn't it? > > Thanks which one do you mean? -- MST