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authorIgor Mammedov <imammedo@redhat.com>2018-09-13 13:06:01 +0200
committerEduardo Habkost <ehabkost@redhat.com>2018-10-24 06:44:59 -0300
commitbc1fb850a31468ac4976f3895f01a6d981e06d0a (patch)
treea3fa1450e86dac4906819b21bb955ed01721dff8 /qemu-deprecated.texi
parenta1f3bb1845e23c38c3bb6ca5e90ac184cfaf1a57 (diff)
vl.c deprecate incorrect CPUs topology
-smp [cpus],sockets/cores/threads[,maxcpus] should describe topology so that total number of logical CPUs [sockets * cores * threads] would be equal to [maxcpus], however historically we didn't have such check in QEMU and it is possible to start VM with an invalid topology. Deprecate invalid options combination so we can make sure that the topology VM started with is always correct in the future. Users with an invalid sockets/cores/threads/maxcpus values should fix their CLI to make sure that [sockets * cores * threads] == [maxcpus] Signed-off-by: Igor Mammedov <imammedo@redhat.com> Reviewed-by: Andrew Jones <drjones@redhat.com> Reviewed-by: Eduardo Habkost <ehabkost@redhat.com> Message-Id: <1536836762-273036-2-git-send-email-imammedo@redhat.com> Reviewed-by: Eric Blake <eblake@redhat.com> [ehabkost: squashed unit test fix] Message-Id: <20181019215345.521d58d7@igors-macbook-pro.local> Signed-off-by: Eduardo Habkost <ehabkost@redhat.com>
Diffstat (limited to 'qemu-deprecated.texi')
-rw-r--r--qemu-deprecated.texi12
1 files changed, 12 insertions, 0 deletions
diff --git a/qemu-deprecated.texi b/qemu-deprecated.texi
index 11b870c5c1..5d2d7a3588 100644
--- a/qemu-deprecated.texi
+++ b/qemu-deprecated.texi
@@ -86,6 +86,18 @@ for these file types is 'host_cdrom' or 'host_device' as appropriate.
The @option{name} parameter of the @option{-net} option is a synonym
for the @option{id} parameter, which should now be used instead.
+@subsection -smp (invalid topologies) (since 3.1)
+
+CPU topology properties should describe whole machine topology including
+possible CPUs.
+
+However, historically it was possible to start QEMU with an incorrect topology
+where @math{@var{n} <= @var{sockets} * @var{cores} * @var{threads} < @var{maxcpus}},
+which could lead to an incorrect topology enumeration by the guest.
+Support for invalid topologies will be removed, the user must ensure
+topologies described with -smp include all possible cpus, i.e.
+ @math{@var{sockets} * @var{cores} * @var{threads} = @var{maxcpus}}.
+
@section QEMU Machine Protocol (QMP) commands
@subsection block-dirty-bitmap-add "autoload" parameter (since 2.12.0)