David Hildenbrand <david@xxxxxxxxxx> writes: > On 12.05.23 16:57, Björn Töpel wrote: >> From: Björn Töpel <bjorn@xxxxxxxxxxxx> >> >> Memory Hot(Un)Plug support for the RISC-V port >> ============================================== [...] > > Cool stuff! I'm fairly busy right now, so some high-level questions upfront: No worries, and no rush! I'd say the v1 series was mainly for the RISC-V folks, and I've got tons of (offline) comments from Alex -- and with your comments below some more details to figure out. > What is the memory section size (which implies the memory block size > and)? This implies the minimum DIMM granularity and the high-level > granularity in which virtio-mem adds memory. It's 128M (27 bits) -- (like arm64 and x86-64?). > What is the pageblock size, implying the minimum granularity that > virtio-mem can operate on? Nothing special AFAIU; MAX_ORDER is 10, so PAGE_SIZE (4K) * 1024. Hmm, I realize that I need to look into some more details of virtio-mem! :-) > On x86-64 and arm64 we currently use the ACPI SRAT to expose the maximum > physical address where we can see memory getting hotplugged. [1] From > that, we can derive the "max_possible_pfn" and prepare the kernel > virtual memory layourt (especially, direct map). > > Is something similar required on RISC-V? Yes! RISC-V is in the progress of getting proper ACPI support. Thanks for pointing me in the these directions; Food for thought that I'll digest for the next version. Cheers, Björn
