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Tsirkin" , "Zhu, Lingshan" Cc: Si-Wei Liu , virtualization@lists.linux-foundation.org, netdev@vger.kernel.org, kvm@vger.kernel.org, parav@nvidia.com, xieyongji@bytedance.com, gautam.dawar@amd.com References: <20e92551-a639-ec13-3d9c-13bb215422e1@intel.com> <9b6292f3-9bd5-ecd8-5e42-cd5d12f036e7@oracle.com> <22e0236f-b556-c6a8-0043-b39b02928fd6@intel.com> <892b39d6-85f8-bff5-030d-e21288975572@oracle.com> <52a47bc7-bf26-b8f9-257f-7dc5cea66d23@intel.com> <20220817045406-mutt-send-email-mst@kernel.org> <20220817053821-mutt-send-email-mst@kernel.org> <449c2fb2-3920-7bf9-8c5c-a68456dfea76@intel.com> <20220817063450-mutt-send-email-mst@kernel.org> From: Jason Wang In-Reply-To: <20220817063450-mutt-send-email-mst@kernel.org> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org 在 2022/8/17 18:37, Michael S. Tsirkin 写道: > On Wed, Aug 17, 2022 at 05:43:22PM +0800, Zhu, Lingshan wrote: >> >> On 8/17/2022 5:39 PM, Michael S. Tsirkin wrote: >>> On Wed, Aug 17, 2022 at 05:13:59PM +0800, Zhu, Lingshan wrote: >>>> On 8/17/2022 4:55 PM, Michael S. Tsirkin wrote: >>>>> On Wed, Aug 17, 2022 at 10:14:26AM +0800, Zhu, Lingshan wrote: >>>>>> Yes it is a little messy, and we can not check _F_VERSION_1 because of >>>>>> transitional devices, so maybe this is the best we can do for now >>>>> I think vhost generally needs an API to declare config space endian-ness >>>>> to kernel. vdpa can reuse that too then. >>>> Yes, I remember you have mentioned some IOCTL to set the endian-ness, >>>> for vDPA, I think only the vendor driver knows the endian, >>>> so we may need a new function vdpa_ops->get_endian(). >>>> In the last thread, we say maybe it's better to add a comment for now. >>>> But if you think we should add a vdpa_ops->get_endian(), I can work >>>> on it for sure! >>>> >>>> Thanks >>>> Zhu Lingshan >>> I think QEMU has to set endian-ness. No one else knows. >> Yes, for SW based vhost it is true. But for HW vDPA, only >> the device & driver knows the endian, I think we can not >> "set" a hardware's endian. > QEMU knows the guest endian-ness and it knows that > device is accessed through the legacy interface. > It can accordingly send endian-ness to the kernel and > kernel can propagate it to the driver. I wonder if we can simply force LE and then Qemu can do the endian conversion? Thanks > >> So if you think we should add a vdpa_ops->get_endian(), >> I will drop these comments in the next version of >> series, and work on a new patch for get_endian(). >> >> Thanks, >> Zhu Lingshan > Guests don't get endian-ness from devices so this seems pointless. >