qemu/backends
David Hildenbrand 9181fb7043 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: Peter Xu <peterx@redhat.com>
Reviewed-by: Eduardo Habkost <ehabkost@redhat.com>
Reviewed-by: Markus 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: David Hildenbrand <david@redhat.com>
Message-Id: <20210510114328.21835-11-david@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2021-06-15 20:27:38 +02:00
..
tpm docs: fix references to docs/devel/tracing.rst 2021-06-02 06:51:09 +02:00
confidential-guest-support.c confidential guest support: Introduce new confidential guest support class 2021-02-08 16:57:37 +11:00
cryptodev-builtin.c cryptodev: Fix Lesser GPL version number 2020-10-27 16:48:49 +01:00
cryptodev-vhost-user.c cryptodev: Fix Lesser GPL version number 2020-10-27 16:48:49 +01:00
cryptodev-vhost.c cryptodev: Fix Lesser GPL version number 2020-10-27 16:48:49 +01:00
cryptodev.c cryptodev: Fix Lesser GPL version number 2020-10-27 16:48:49 +01:00
dbus-vmstate.c dbus-vmstate: Increase the size of input stream buffer used during load 2021-04-01 15:27:44 +04:00
hostmem-file.c hostmem: Wire up RAM_NORESERVE via "reserve" property 2021-06-15 20:27:38 +02:00
hostmem-memfd.c hostmem: Wire up RAM_NORESERVE via "reserve" property 2021-06-15 20:27:38 +02:00
hostmem-ram.c hostmem: Wire up RAM_NORESERVE via "reserve" property 2021-06-15 20:27:38 +02:00
hostmem.c hostmem: Wire up RAM_NORESERVE via "reserve" property 2021-06-15 20:27:38 +02:00
Kconfig tpm: Move backend code under the 'backends/' directory 2020-06-19 07:25:55 -04:00
meson.build confidential guest support: Introduce new confidential guest support class 2021-02-08 16:57:37 +11:00
rng-builtin.c replay: rng-builtin support 2021-02-08 15:15:32 +01:00
rng-egd.c rng-egd: Register "chardev" as class property 2020-10-13 15:56:30 -04:00
rng-random.c rng-random: register "filename" as class property 2020-10-13 15:56:30 -04:00
rng.c rng: Register "opened" as class property 2020-10-13 15:56:30 -04:00
trace-events docs: fix references to docs/devel/tracing.rst 2021-06-02 06:51:09 +02:00
trace.h trace: switch position of headers to what Meson requires 2020-08-21 06:18:24 -04:00
vhost-user.c vhost-user: Register "chardev" as class property 2020-10-13 15:56:30 -04:00