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author | David Hildenbrand <david@redhat.com> | 2020-05-07 16:01:25 +0200 |
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committer | Michael S. Tsirkin <mst@redhat.com> | 2020-06-04 15:36:52 -0400 |
commit | 5f1f79bbc9e26fa9412fa9522f957bb8f030c442 (patch) | |
tree | e68e7ccef1416641ff32389fea47091008ea6e84 /include/uapi/linux/virtio_ids.h | |
parent | 18e643cd6c4dcdb09510a4bf739438e7cd1ae1f2 (diff) | |
download | linux-stable-5f1f79bbc9e26fa9412fa9522f957bb8f030c442.tar.gz linux-stable-5f1f79bbc9e26fa9412fa9522f957bb8f030c442.tar.bz2 linux-stable-5f1f79bbc9e26fa9412fa9522f957bb8f030c442.zip |
virtio-mem: Paravirtualized memory hotplug
Each virtio-mem device owns exactly one memory region. It is responsible
for adding/removing memory from that memory region on request.
When the device driver starts up, the requested amount of memory is
queried and then plugged to Linux. On request, further memory can be
plugged or unplugged. This patch only implements the plugging part.
On x86-64, memory can currently be plugged in 4MB ("subblock") granularity.
When required, a new memory block will be added (e.g., usually 128MB on
x86-64) in order to plug more subblocks. Only x86-64 was tested for now.
The online_page callback is used to keep unplugged subblocks offline
when onlining memory - similar to the Hyper-V balloon driver. Unplugged
pages are marked PG_offline, to tell dump tools (e.g., makedumpfile) to
skip them.
User space is usually responsible for onlining the added memory. The
memory hotplug notifier is used to synchronize virtio-mem activity
against memory onlining/offlining.
Each virtio-mem device can belong to a NUMA node, which allows us to
easily add/remove small chunks of memory to/from a specific NUMA node by
using multiple virtio-mem devices. Something that works even when the
guest has no idea about the NUMA topology.
One way to view virtio-mem is as a "resizable DIMM" or a DIMM with many
"sub-DIMMS".
This patch directly introduces the basic infrastructure to implement memory
unplug. Especially the memory block states and subblock bitmaps will be
heavily used there.
Notes:
- In case memory is to be onlined by user space, we limit the amount of
offline memory blocks, to not run out of memory. This is esp. an
issue if memory is added faster than it is getting onlined.
- Suspend/Hibernate is not supported due to the way virtio-mem devices
behave. Limited support might be possible in the future.
- Reloading the device driver is not supported.
Reviewed-by: Pankaj Gupta <pankaj.gupta.linux@gmail.com>
Tested-by: Pankaj Gupta <pankaj.gupta.linux@gmail.com>
Cc: "Michael S. Tsirkin" <mst@redhat.com>
Cc: Jason Wang <jasowang@redhat.com>
Cc: Oscar Salvador <osalvador@suse.de>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Igor Mammedov <imammedo@redhat.com>
Cc: Dave Young <dyoung@redhat.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Pavel Tatashin <pasha.tatashin@soleen.com>
Cc: Stefan Hajnoczi <stefanha@redhat.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: "Rafael J. Wysocki" <rjw@rjwysocki.net>
Cc: Len Brown <lenb@kernel.org>
Cc: linux-acpi@vger.kernel.org
Signed-off-by: David Hildenbrand <david@redhat.com>
Link: https://lore.kernel.org/r/20200507140139.17083-2-david@redhat.com
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Diffstat (limited to 'include/uapi/linux/virtio_ids.h')
-rw-r--r-- | include/uapi/linux/virtio_ids.h | 1 |
1 files changed, 1 insertions, 0 deletions
diff --git a/include/uapi/linux/virtio_ids.h b/include/uapi/linux/virtio_ids.h index ecc27a17401a..b052355ac7a3 100644 --- a/include/uapi/linux/virtio_ids.h +++ b/include/uapi/linux/virtio_ids.h @@ -44,6 +44,7 @@ #define VIRTIO_ID_VSOCK 19 /* virtio vsock transport */ #define VIRTIO_ID_CRYPTO 20 /* virtio crypto */ #define VIRTIO_ID_IOMMU 23 /* virtio IOMMU */ +#define VIRTIO_ID_MEM 24 /* virtio mem */ #define VIRTIO_ID_FS 26 /* virtio filesystem */ #define VIRTIO_ID_PMEM 27 /* virtio pmem */ #define VIRTIO_ID_MAC80211_HWSIM 29 /* virtio mac80211-hwsim */ |