Copying Paolo, author of memory-backend-file. Baptiste Reynal <b.rey...@virtualopensystems.com> writes:
> 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. Can you explain why that's useful in a bit more detail? > Such new backend enables, on a master side, to allocate the whole > memory as shareable (e.g. /dev/shm, or hugetlbfs). memory-backend-file can do that already. What exactly does memory-backend-shared add to it? > On the slave side it enables the startup of QEMU without any main memory > allocated. Then the slave goes in a waiting state, the same used in the > case of an incoming migration, and the file descriptor of the shared > memory is sent by the master over a socket. > The waiting state ends when the master sends to the slave a signal > with size and offset to mmap and use as memory as payload. > > You can test those patches using modules and test application available > on https://git.virtualopensystems.com/dev/qemu-het-tools. > - SDM Platform module on branch sdm_test_mod_v1 > - Test application on branch sdm_test_app > - Slave files on branch demo_slaves_sdm > > QEMU code is avalaible here https://git.virtualopensystems.com/dev/qemu on > branch rfc_v2. > > Run QEMU master instance: > ./qemu-system-arm -nographic \ > -kernel zImage \ > -M virt -m 1G \ > -initrd busybox.cpio \ > -object multi-socket-backend,id=sock,path=sock,listen \ > -object > memory-backend-shared,id=mem,size=1G,mem-path=/dev/hugepages,socket=sock,master > \ > -object sdm-signal-shboot,id=boot,shm=mem \ > -object sdm-communication-socket,id=scomm,socket=sock \ > -device > virtio-sdm-device,comm=scomm,master,num-slaves=1,len-signals=1,signals[0]=boot > \ > -append "mem=512M memmap=512M$0x60000000" \ > -numa node,memdev=mem -m 1G > > Run QEMU slave instance: > ./qemu-system-arm -nographic \ > -kernel zImage \ > -M virt -m 1G \ > -initrd busybox.cpio \ > -object multi-socket-backend,id=sock,path=sock \ > -object memory-backend-shared,id=mem,size=512M,socket=sock \ > -object sdm-signal-shboot,id=boot,shm=mem \ > -object sdm-communication-socket,id=scomm,socket=sock \ > -device sdm-platform,comm=scomm,len-signals=1,signals[0]="boot" \ > -incoming "shared:mem" \ > -numa node,memdev=mem -m 512M > > On the master, load the SDM module (insmod sdm_test_mod_v1) and trigger the > boot with > the following command: > ./sdm-test -b 0 1 zImage slave.dtb > > zImage and slave.dtb are available on branch demo_slaves_sdm. > > This patch serie is a follow-up to "[RFC PATCH 0/8] Towards an Heterogeneous > QEMU": > https://lists.gnu.org/archive/html/qemu-devel/2015-10/msg00171.html > > This patch serie depends on: > - [RFC v2 0/6] SDM Interface > - [RFC v2 1/1] backend: multi-client-socket > > This work has been sponsored by Huawei Technologies Duesseldorf GmbH. > > Baptiste Reynal (3): > backend: shared memory backend > migration: add shared migration type > hw/misc: sdm signal shboot > > Christian Pinto (3): > qemu: slave machine flag > hw/arm: boot > qemu: numa > > backends/Makefile.objs | 2 +- > backends/hostmem-shared.c | 198 > ++++++++++++++++++++++++++++++++++++ > hw/arm/boot.c | 13 +++ > hw/core/machine.c | 27 +++++ > hw/misc/Makefile.objs | 1 + > hw/misc/sdm-signal-shboot.c | 62 +++++++++++ > include/hw/boards.h | 2 + > include/hw/misc/sdm-signal-shboot.h | 38 +++++++ > include/migration/migration.h | 2 + > include/sysemu/hostmem-shared.h | 66 ++++++++++++ > migration/Makefile.objs | 2 +- > migration/migration.c | 2 + > migration/shared.c | 33 ++++++ > numa.c | 17 +++- > qemu-options.hx | 5 +- > util/qemu-config.c | 5 + > 16 files changed, 471 insertions(+), 4 deletions(-) > create mode 100644 backends/hostmem-shared.c > create mode 100644 hw/misc/sdm-signal-shboot.c > create mode 100644 include/hw/misc/sdm-signal-shboot.h > create mode 100644 include/sysemu/hostmem-shared.h > create mode 100644 migration/shared.c
