In safety-critical environment, it is not considered safe to dynamically change important configurations at runtime. Everything should be statically defined and statically verified.
In this case, if the system configuration knows a priori that there are only 2 VMs and they need to communicate over shared memory, it is safer to pre-configure the shared memory at build time rather than let the VMs attempt to share memory at runtime. And it is faster too. Furthermore, on dom0less system, the legacy way to build up communication channels between domains, like grant table, are normally absent there. So this patch serie introduces a set of static shared memory device tree nodes to allow users to statically set up shared memory on dom0less system, enabling domains to do shm-based communication. The only way to trigger this static shared memory configuration should be via device tree, which is at the same level as the XSM rules. It was inspired by the patch serie of ["xl/libxl-based shared mem]( https://marc.info/?l=xen-devel&m=154404821731186ory";). Looking into related [design link]( https://lore.kernel.org/all/a50d9fde-1d06-7cda-2779-9eea9e1c0...@xen.org/T/) for more details. Penny Zheng (8): xen/arm: introduce static shared memory xen/arm: allocate static shared memory to the default owner dom_io xen/arm: allocate static shared memory to a specific owner domain xen/arm: introduce put_page_nr and get_page_nr xen/arm: Add additional reference to owner domain when the owner is allocated xen/arm: set up shared memory foreign mapping for borrower domain xen/arm: create shared memory nodes in guest device tree xen/arm: enable statically shared memory on Dom0 docs/misc/arm/device-tree/booting.txt | 120 ++++++++ xen/arch/arm/Kconfig | 6 + xen/arch/arm/bootfdt.c | 68 +++++ xen/arch/arm/domain_build.c | 378 +++++++++++++++++++++++++- xen/arch/arm/include/asm/kernel.h | 1 + xen/arch/arm/include/asm/mm.h | 4 + xen/arch/arm/include/asm/setup.h | 4 + xen/arch/arm/mm.c | 36 ++- xen/common/domain.c | 5 + 9 files changed, 612 insertions(+), 10 deletions(-) -- 2.25.1
