On Tue, Feb 04, 2020 at 12:30:42PM +0100, i.kotrasi...@partner.samsung.com wrote: > From: Igor Kotrasinski <i.kotrasi...@partner.samsung.com> > > This patchset adds a "memory exposing" device that allows two QEMU > instances to share arbitrary memory regions. Unlike ivshmem, it does not > create a new region of memory that's shared between VMs, but instead > allows one VM to access any memory region of the other VM we choose to > share. > > The motivation for this device is a sort of ARM Trustzone "emulation", > where a rich system running on one machine (e.g. x86_64 linux) is able > to perform SMCs to a trusted system running on another (e.g. OpTEE on > ARM). With a device that allows sharing arbitrary memory between VMs, > this can be achieved with minimal changes to the trusted system and its > linux driver while allowing the rich system to run on a speedier x86 > emulator. I prepared additional patches for linux, OpTEE OS and OpTEE > build system as a PoC that such emulation works and passes OpTEE tests; > I'm not sure what would be the best way to share them. > > This patchset is my first foray into QEMU source code and I'm certain > it's not yet ready to be merged in. I'm not sure whether memory sharing > code has any race conditions or breaks rules of working with memory > regions, or if having VMs communicate synchronously via chardevs is the > right way to do it. I do believe the basic idea for sharing memory > regions is sound and that it could be useful for inter-VM communication.
Hi, Without having looked into the patches yet, I'm already wondering if you can use the existing -object memory-backend-file,size=512M,mem-path=/my/shared/mem feature for your use case? That's the existing mechanism for fully sharing guest RAM and if you want to share all of memory then maybe a device is not necessary - just share the memory. Stefan > Igor Kotrasinski (9): > memory: Add function for finding flat memory ranges > memory: Support mmap offset for fd-backed memory regions > memory: Hack - use shared memory when possible > hw/misc/memexpose: Add documentation > hw/misc/memexpose: Add core memexpose files > hw/misc/memexpose: Add memexpose pci device > hw/misc/memexpose: Add memexpose memory region device > hw/misc/memexpose: Add simple tests > hw/arm/virt: Hack in support for memexpose device > > Kconfig.host | 3 + > MAINTAINERS | 12 + > Makefile | 1 + > backends/hostmem-memfd.c | 2 +- > configure | 8 + > docs/specs/memexpose-spec.txt | 168 +++++++++ > exec.c | 10 +- > hw/arm/virt.c | 110 +++++- > hw/core/numa.c | 4 +- > hw/mem/Kconfig | 3 + > hw/misc/Makefile.objs | 1 + > hw/misc/ivshmem.c | 3 +- > hw/misc/memexpose/Makefile.objs | 4 + > hw/misc/memexpose/memexpose-core.c | 630 > ++++++++++++++++++++++++++++++++ > hw/misc/memexpose/memexpose-core.h | 109 ++++++ > hw/misc/memexpose/memexpose-memregion.c | 142 +++++++ > hw/misc/memexpose/memexpose-memregion.h | 41 +++ > hw/misc/memexpose/memexpose-msg.c | 261 +++++++++++++ > hw/misc/memexpose/memexpose-msg.h | 161 ++++++++ > hw/misc/memexpose/memexpose-pci.c | 218 +++++++++++ > include/exec/memory.h | 20 + > include/exec/ram_addr.h | 2 +- > include/hw/arm/virt.h | 5 + > include/qemu/mmap-alloc.h | 1 + > memory.c | 82 ++++- > tests/qtest/Makefile.include | 2 + > tests/qtest/memexpose-test.c | 364 ++++++++++++++++++ > util/mmap-alloc.c | 7 +- > util/oslib-posix.c | 2 +- > 29 files changed, 2360 insertions(+), 16 deletions(-) > create mode 100644 docs/specs/memexpose-spec.txt > create mode 100644 hw/misc/memexpose/Makefile.objs > create mode 100644 hw/misc/memexpose/memexpose-core.c > create mode 100644 hw/misc/memexpose/memexpose-core.h > create mode 100644 hw/misc/memexpose/memexpose-memregion.c > create mode 100644 hw/misc/memexpose/memexpose-memregion.h > create mode 100644 hw/misc/memexpose/memexpose-msg.c > create mode 100644 hw/misc/memexpose/memexpose-msg.h > create mode 100644 hw/misc/memexpose/memexpose-pci.c > create mode 100644 tests/qtest/memexpose-test.c > > -- > 2.7.4 > >
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