On Sat, May 2, 2020 at 2:27 AM David Hildenbrand <david@xxxxxxxxxx> wrote: > > >> Now, let's clarify what I want regarding virtio-mem: > >> > >> 1. kexec should not add virtio-mem memory to the initial firmware > >> memmap. The driver has to be in charge as discussed. > >> 2. kexec should not place kexec images onto virtio-mem memory. That > >> would end badly. > >> 3. kexec should still dump virtio-mem memory via kdump. > > > > Ok, but then seems to say to me that dax/kmem is a different type of > > (driver managed) than virtio-mem and it's confusing to try to apply > > the same meaning. Why not just call your type for the distinct type it > > is "System RAM (virtio-mem)" and let any other driver managed memory > > follow the same "System RAM ($driver)" format if it wants? > > I had the same idea but discarded it because it seemed to uglify the > add_memory() interface (passing yet another parameter only relevant for > driver managed memory). Maybe we really want a new one, because I like > that idea: > > /* > * Add special, driver-managed memory to the system as system ram. > * The resource_name is expected to have the name format "System RAM > * ($DRIVER)", so user space (esp. kexec-tools)" can special-case it. > * > * For this memory, no entries in /sys/firmware/memmap are created, > * as this memory won't be part of the raw firmware-provided memory map > * e.g., after a reboot. Also, the created memory resource is flagged > * with IORESOURCE_MEM_DRIVER_MANAGED, so in-kernel users can special- > * case this memory (e.g., not place kexec images onto it). > */ > int add_memory_driver_managed(int nid, u64 start, u64 size, > const char *resource_name); > > > If we'd ever have to special case it even more in the kernel, we could > allow to specify further resource flags. While passing the driver name > instead of the resource_name would be an option, this way we don't have > to hand craft new resource strings for added memory resources. > > Thoughts? Looks useful to me and simplifies walking /proc/iomem. I personally like the safety of the string just being the $driver component of the name, but I won't lose sleep if the interface stays freeform like you propose.
