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authorDavid Hildenbrand <david@redhat.com>2020-11-12 16:38:03 +0300
committerMichael S. Tsirkin <mst@redhat.com>2020-12-19 00:14:26 +0300
commitd5614944254cf288b8fd46fda8c86d916346131d (patch)
tree3ae3d5e92058d9be9ea11413619537e7e416c320 /drivers/virtio
parent98ff9f9411860073f952f1e62a05afb9f6a9e77e (diff)
downloadlinux-d5614944254cf288b8fd46fda8c86d916346131d.tar.xz
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 <richard.weiyang@linux.alibaba.com> Reviewed-by: Pankaj Gupta <pankaj.gupta.linux@gmail.com> Cc: "Michael S. Tsirkin" <mst@redhat.com> Cc: Jason Wang <jasowang@redhat.com> Cc: Pankaj Gupta <pankaj.gupta.linux@gmail.com> Signed-off-by: David Hildenbrand <david@redhat.com> Link: https://lore.kernel.org/r/20201112133815.13332-18-david@redhat.com Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Diffstat (limited to 'drivers/virtio')
-rw-r--r--drivers/virtio/virtio_mem.c15
1 files changed, 15 insertions, 0 deletions
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,