On 7/20/21 12:05 AM, Long Li wrote: >> Subject: Re: [Patch v4 0/3] Introduce a driver to support host accelerated >> access to Microsoft Azure Blob >> >> On Mon, Jul 19, 2021 at 09:37:56PM -0700, Bart Van Assche wrote: >>> such that this object storage driver can be implemented as a >>> user-space library instead of as a kernel driver? As you may know vfio >>> users can either use eventfds for completion notifications or polling. >>> An interface like io_uring can be built easily on top of vfio. >> >> Yes. Similar to say the NVMe K/V command set this does not look like a >> candidate for a kernel driver. > > The driver is modeled to support multiple processes/users over a VMBUS > channel. I don't see a way that this can be implemented through VFIO? > > Even if it can be done, this exposes a security risk as the same VMBUS > channel is shared by multiple processes in user-mode. Sharing a VMBUS channel among processes is not necessary. I propose to assign one VMBUS channel to each process and to multiplex I/O submitted to channels associated with the same blob storage object inside e.g. the hypervisor. This is not a new idea. In the NVMe specification there is a diagram that shows that multiple NVMe controllers can provide access to the same NVMe namespace. See also diagram "Figure 416: NVM Subsystem with Three I/O Controllers" in version 1.4 of the NVMe specification. Bart.
