Skip to content
Snippets Groups Projects
Commit 9181fb70 authored by David Hildenbrand's avatar David Hildenbrand Committed by Paolo Bonzini
Browse files

hostmem: Wire up RAM_NORESERVE via "reserve" property


Let's provide a way to control the use of RAM_NORESERVE via memory
backends using the "reserve" property which defaults to true (old
behavior).

Only Linux currently supports clearing the flag (and support is checked at
runtime, depending on the setting of "/proc/sys/vm/overcommit_memory").
Windows and other POSIX systems will bail out with "reserve=false".

The target use case is virtio-mem, which dynamically exposes memory
inside a large, sparse memory area to the VM. This essentially allows
avoiding to set "/proc/sys/vm/overcommit_memory == 0") when using
virtio-mem and also supporting hugetlbfs in the future.

As really only Linux implements RAM_NORESERVE right now, let's expose
the property only with CONFIG_LINUX. Setting the property to "false"
will then only fail in corner cases -- for example on very old kernels
or when memory overcommit was completely disabled by the admin.

Reviewed-by: default avatarPeter Xu <peterx@redhat.com>
Reviewed-by: default avatarEduardo Habkost <ehabkost@redhat.com>
Reviewed-by: default avatarMarkus Armbruster <armbru@redhat.com>
Acked-by: Eduardo Habkost <ehabkost@redhat.com> for memory backend and machine core
Cc: Markus Armbruster <armbru@redhat.com>
Cc: Eric Blake <eblake@redhat.com>
Cc: Igor Mammedov <imammedo@redhat.com>
Signed-off-by: default avatarDavid Hildenbrand <david@redhat.com>
Message-Id: <20210510114328.21835-11-david@redhat.com>
Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
parent d94e0bc9
No related branches found
No related tags found
No related merge requests found
Loading
0% Loading or .
You are about to add 0 people to the discussion. Proceed with caution.
Finish editing this message first!
Please register or to comment