The virtio-mem driver currently supports logical hot(un)plug in MAX_ORDER - 1 granularity (4MiB on x86-64) or bigger. We want to support pageblock granularity (2MiB on x86-64), to make hot(un)plug even more flexible, and to improve hotunplug when using ZONE_NORMAL. With pageblock granularity, we then have a granularity comparable to hugepage ballooning. Further, there are ideas to increase MAX_ORDER, so we really want to decouple it from MAX_ORDER. While ZONE_MOVABLE should mostly work already, alloc_contig_range() still needs work to be able to properly handle pageblock granularity on ZONE_NORMAL. This support is in the works [1], so let's prepare virtio-mem for supporting smaller granularity than MAX_ORDER - 1. Tested with ZONE_MOVABLE after removing the MAX_ORDER - 1 granularity limitation in virtio-mem, and using different device block sizes (2MiB, 4MiB, 8MiB). [1] https://lkml.kernel.org/r/20211115193725.737539-1-zi.yan@xxxxxxxx Cc: "Michael S. Tsirkin" <mst@xxxxxxxxxx> Cc: Jason Wang <jasowang@xxxxxxxxxx> Cc: Zi Yan <ziy@xxxxxxxxxx> Cc: Gavin Shan <gshan@xxxxxxxxxx> Cc: Hui Zhu <teawater@xxxxxxxxx> Cc: Eric Ren <renzhengeek@xxxxxxxxx> Cc: Sebastien Boeuf <sebastien.boeuf@xxxxxxxxx> Cc: Pankaj Gupta <pankaj.gupta.linux@xxxxxxxxx> Cc: Wei Yang <richard.weiyang@xxxxxxxxxxxxxxxxx> Cc: virtualization@xxxxxxxxxxxxxxxxxxxxxxxxxx Cc: linux-mm@xxxxxxxxx David Hildenbrand (2): virtio-mem: prepare page onlining code for granularity smaller than MAX_ORDER - 1 virtio-mem: prepare fake page onlining code for granularity smaller than MAX_ORDER - 1 drivers/virtio/virtio_mem.c | 110 ++++++++++++++++++++++++------------ 1 file changed, 74 insertions(+), 36 deletions(-) -- 2.31.1
