Hi Jim, > -----Original Message----- > From: dev [mailto:dev-boun...@dpdk.org] On Behalf Of Jim Murphy > Sent: Wednesday, September 20, 2017 6:24 AM > To: dev@dpdk.org > Subject: [dpdk-dev] [PATCH v2] net/virtio-user: fix not working on 32-bit > system > > Hi, > > The fix contained in this patch breaks under the following scenario: > > 1. A 64 bit host and virtual machine. Therefore all physical addresses are > 64 bits.
Host, VM and application are 64bit, then I suppose there's no problem? > 2. A 32 bit user mode DPDK process running on a 64 bit virtual machine (64 > bit kernel). Ah, this is a case we fail to cover. > > In this case, the physical address is 64bits but the virtual address of the > user process is 32 bits so uintptr_t is only 32 bits. As a result when: > > (uintptr_t)(mb) + (vq)->offset) > > is referenced, only 32 bits are copied into the descriptor but 64 bits are > required because in this scenario that is the size of a physical address. > > So it seems like we need a way to determine the size of the physical > address and then VIRTIO_MBUF_ADDR should be written to copy that many > bytes > into the uint64_t. Does anyone know how to determine the size of the > physical address? It's easy to find a way to decide the length (similar to _offset_), but copying variable length of bytes seems not an efficient way. Thanks, Jianfeng
