Re: [PATCH v2 4/4] qemu: Generate command line for tb-cache feature

Alright, here's the deal: to enable tb-cache one has to use '-accel tcg,tb-size=' which then conflicts with '-machine accel=tcg'. But sure, we can use the old -accel in this specific case.

But because of how the tb-size argument is defined in QEMU there's no way for us to have a capability check. The feature was introduced in QEMU commit of v5.0.0-rc0~175^2~62 and is tied to TCG only. Therefore, I think we can live without capability check. Worst case scenario, QEMU fails to start. Resolves: https://gitlab.com/libvirt/libvirt/-/issues/229 Signed-off-by: Michal Privoznik <mprivozn(a)redhat.com&gt; Tested-by: Kashyap Chamarthy <kchamart(a)redhat.com&gt; --- src/qemu/qemu_command.c | 5 +++ ...efault-cpu-tcg-features.x86_64-latest.args | 40 +++++++++++++++++++ tests/qemuxml2argvtest.c | 1 + 3 files changed, 46 insertions(+) create mode 100644 tests/qemuxml2argvdata/x86_64-default-cpu-tcg-features.x86_64-latest.args diff --git a/src/qemu/qemu_command.c b/src/qemu/qemu_command.c index 0257b86a0d..17ee3c5d3a 100644 --- a/src/qemu/qemu_command.c +++ b/src/qemu/qemu_command.c @@ -7271,6 +7271,11 @@ qemuBuildAccelCommandLine(virCommand *cmd, switch ((virDomainVirtType)def->virtType) { case VIR_DOMAIN_VIRT_QEMU: virBufferAddLit(&buf, "tcg"); + + if (def->features[VIR_DOMAIN_FEATURE_TCG] == VIR_TRISTATE_SWITCH_ON) {

+ virBufferAsprintf(&buf, ",tb-size=%llu", + def->tcg_features->tb_cache >> 10);

+ } break;