This series is based on [1]: [PATCH v2 00/10] virtio-mem: paravirtualized memory That will hopefull get picked up soon, rebased to -next. The following patches were reverted from -next [2]: [PATCH 0/3] kexec/memory_hotplug: Prevent removal and accidental use As discussed in that thread, they should be reverted from -next already. In theory, if people agree, we could take the first two patches via the -mm tree now and the last (virtio-mem) patch via MST's tree once picking up virtio-mem. No strong feelings. Memory added by virtio-mem is special and might contain logical holes, especially after memory unplug, but also when adding memory in sub-section size. While memory in these holes can usually be read, that memory should not be touched. virtio-mem managed device memory is never exposed via any firmware memmap (esp., e820). The device driver will request to plug memory from the hypervisor and add it to Linux. On a cold start, all memory is unplugged, and the guest driver will first request to plug memory from the hypervisor, to then add it to Linux. After a reboot, all memory will get unplugged (except in rare, special cases). In case the device driver comes up and detects that some memory is still plugged after a reboot, it will manually request to unplug all memory from the hypervisor first - to then request to plug memory from the hypervisor and add to Linux. This is essentially a defragmentation step, where all logical holes are removed. As the device driver is responsible for detecting, adding and managing that memory, also kexec should treat it like that. It is special. We need a way to teach kexec-tools to not add that memory to the fixed-up firmware memmap, to not place kexec images onto this memory, but still allow kdump to dump it. Add a flag to tell memory hotplug code to not create /sys/firmware/memmap entries and to indicate it via "System RAM (driver managed)" in /proc/iomem. Before this series, kexec_file_load() already did the right thing (for virtio-mem) by not adding that memory to the fixed-up firmware memmap and letting the device driver handle it. With this series, also kexec_load() - which relies on user space to provide a fixed up firmware memmap - does the right thing with virtio-mem memory. When the virtio-mem device driver(s) come up, they will request to unplug all memory from the hypervisor first (esp. defragment), to then request to plug consecutive memory ranges from the hypervisor, and add them to Linux - just like on a reboot where we still have memory plugged. [1] https://lore.kernel.org/r/20200311171422.10484-1-david@xxxxxxxxxx/ [2] https://lore.kernel.org/r/20200326180730.4754-1-james.morse@xxxxxxx David Hildenbrand (3): mm/memory_hotplug: Prepare passing flags to add_memory() and friends mm/memory_hotplug: Introduce MHP_DRIVER_MANAGED virtio-mem: Add memory with MHP_DRIVER_MANAGED arch/powerpc/platforms/powernv/memtrace.c | 2 +- .../platforms/pseries/hotplug-memory.c | 2 +- drivers/acpi/acpi_memhotplug.c | 2 +- drivers/base/memory.c | 2 +- drivers/dax/kmem.c | 2 +- drivers/hv/hv_balloon.c | 2 +- drivers/s390/char/sclp_cmd.c | 2 +- drivers/virtio/virtio_mem.c | 3 +- drivers/xen/balloon.c | 2 +- include/linux/memory_hotplug.h | 15 +++++++-- mm/memory_hotplug.c | 31 +++++++++++++------ 11 files changed, 44 insertions(+), 21 deletions(-) -- 2.25.3
