On Thu, Mar 31, 2016 at 11:14 AM, Stefan Hajnoczi <stefa...@gmail.com> wrote: > > On Fri, Mar 18, 2016 at 10:13:52AM +0100, Baptiste Reynal wrote: > > A new memory backend, the shared memory backend, based on > > the file memory backend. > > > > This new backend allows a master QEMU instance to share a part of > > his main memory whith a slave QEMU instance. It is then possible to load > > a firmware on this memory and trigger the slave boot using a SDM > > signal. > > > > Such new backend enables, on a master side, to allocate the whole > > memory as shareable (e.g. /dev/shm, or hugetlbfs). > > How is this different from qemu -mem-path which can be used for > hugetlbfs?
A new mechanism is integrated here. This shared memory allows the slave to map dynamically only a subregion of the master memory, when with mempath the entire memory is shared. A use-case can be the use of remoteproc framework on Linux. Remoteproc carveout a memory region and load the slave firmware to this region, then send the size and offset to the slave before boot. The slave memory region is unknown before master execution, it cannot be set in QEMU command line.