Sebastien Boeuf 2e0508cdc6 vm-virtio: fs: Add DAX shared region support ... This patch enables the vhost-user protocol features to let the slave initiates some request towards the master (VMM). It also takes care of receiving the requests from the slave and take appropriate actions based on the request type. The way the flow works now are as follow: - The VMM creates a region of memory that is made available to the guest by exposing it through the virtio-fs PCI BAR 2. - The virtio-fs device is created by the VMM, exposing some protocol features bits to virtiofsd, letting it know that it can send some request to the VMM through a dedicated socket. - On behalf of the guest driver asking for reading or writing a file, virtiofsd sends a request to the VMM, asking for a file descriptor to be mapped into the shared memory region at a specific offset. - The guest can directly read/write the file at the offset of the memory region. This implementation is more performant than the one using exclusively the virtqueues. With the virtqueues, the content of the file needs to be copied to the queues every time the guest is asking to access it. With the shared memory region, the virtqueues become the control plane where the libfuse commands are sent to virtiofsd. The data plane is literally the whole memory region which does not need any extra copy of the file content. The only penalty is the first time a file is accessed, it needs to be mapped into the VMM virtual address space. Another interesting case where this solution will not perform as well as expected is when a file is larger than the region itself. This means the file needs to be mapped in several times, but more than that this means it needs to be remapped every time it's being accessed. Signed-off-by: Sebastien Boeuf <sebastien.boeuf@intel.com>		2019-08-13 13:57:53 +02:00
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src	vm-virtio: fs: Add DAX shared region support	2019-08-13 13:57:53 +02:00
Cargo.toml	build: Bulk update dependencies	2019-08-02 15:22:37 +02:00