Re: [libvirt] [PATCH v3 0/2] Allow migration with invtsc if TSC frequency is explicitly set

This series makes QEMU accept migration if tsc-frequency is explicitly set on configuration. As management software is required to keep device configuration the same on migration source or destination, explicit tsc-frequency will ensure that either: * The destination host has a matching TSC frequency; or * The destination host has TSC scaling available. Changelog ========= v2 -> v3: * Fix build failure ((missing closing braces) v1 -> v2: * v1 series subject was: * [PATCH 0/4] Allow migration with invtsc if there's no frequency mismatch * Removed patches 3/4 and 4/4, that allowed migration if no explicit tsc-frequency was set. Implementing the check on post_load or post_init is not enough to make migration abort, so we will need a more complex solution to implement that feature. Plans for future work ===================== 1) Querying host TSC frequency/scaling capability ------------------------------------------------- I plan to include TSC frequency/scaling information on query-cpu-model-expansion model="host" in a future series. Then management software will be able to automatically configure TSC frequency when invtsc is enabled, instead of requiring the user to configure it explicitly. While we don't implement that, invtsc migration will be possible only if the user configures TSC frequency manually. 2) invtsc migration with no explicit TSC frequency -------------------------------------------------- A future series can implement migration when TSC frequency is not specified explicitly. It will be a bit more complex because it requires either letting the destination abort the migration, or sending TSC frequency/scaling information from destination to source. --- Cc: Marcelo Tosatti <mtosatti(a)redhat.com&gt; Cc: "Daniel P. Berrange" <berrange(a)redhat.com&gt; Cc: Paolo Bonzini <pbonzini(a)redhat.com&gt; Cc: kvm(a)vger.kernel.org Cc: Haozhong Zhang <haozhong.zhang(a)intel.com&gt; Cc: "Michael S. Tsirkin" <mst(a)redhat.com&gt; Cc: Igor Mammedov <imammedo(a)redhat.com&gt; Cc: libvir-list(a)redhat.com Cc: Jiri Denemark <jdenemar(a)redhat.com&gt; Eduardo Habkost (2): kvm: Simplify invtsc check kvm: Allow invtsc migration if tsc-khz is set explicitly target/i386/kvm.c | 20 +++++++++++--------- 1 file changed, 11 insertions(+), 9 deletions(-) -- 2.11.0.259.g40922b1