From d5614944254cf288b8fd46fda8c86d916346131d Mon Sep 17 00:00:00 2001 From: David Hildenbrand Date: Thu, 12 Nov 2020 14:38:03 +0100 Subject: [PATCH] virito-mem: document Sub Block Mode (SBM) Let's add some documentation for the current mode - Sub Block Mode (SBM) - to prepare for a new mode - Big Block Mode (BBM). Follow-up patches will properly factor out the existing Sub Block Mode (SBM) and implement Big Block Mode (BBM). Reviewed-by: Wei Yang Reviewed-by: Pankaj Gupta Cc: "Michael S. Tsirkin" Cc: Jason Wang Cc: Pankaj Gupta Signed-off-by: David Hildenbrand Link: https://lore.kernel.org/r/20201112133815.13332-18-david@redhat.com Signed-off-by: Michael S. Tsirkin --- drivers/virtio/virtio_mem.c | 15 +++++++++++++++ 1 file changed, 15 insertions(+) diff --git a/drivers/virtio/virtio_mem.c b/drivers/virtio/virtio_mem.c index cbd0aa5eb95c..4234bfc0cf52 100644 --- a/drivers/virtio/virtio_mem.c +++ b/drivers/virtio/virtio_mem.c @@ -27,6 +27,21 @@ static bool unplug_online = true; module_param(unplug_online, bool, 0644); MODULE_PARM_DESC(unplug_online, "Try to unplug online memory"); +/* + * virtio-mem currently supports the following modes of operation: + * + * * Sub Block Mode (SBM): A Linux memory block spans 1..X subblocks (SB). The + * size of a Sub Block (SB) is determined based on the device block size, the + * pageblock size, and the maximum allocation granularity of the buddy. + * Subblocks within a Linux memory block might either be plugged or unplugged. + * Memory is added/removed to Linux MM in Linux memory block granularity. + * + * User space / core MM (auto onlining) is responsible for onlining added + * Linux memory blocks - and for selecting a zone. Linux Memory Blocks are + * always onlined separately, and all memory within a Linux memory block is + * onlined to the same zone - virtio-mem relies on this behavior. + */ + enum virtio_mem_mb_state { /* Unplugged, not added to Linux. Can be reused later. */ VIRTIO_MEM_MB_STATE_UNUSED = 0,