Re: [libvirt] [PATCH v4 4/8] libxl: do not enable nested HVM unless global nested_hvm option enabled

Introduce global libxl option for enabling nested HVM feature, similar to kvm module parameter. This will prevent enabling experimental feature by mere presence of <cpu mode='host-passthrough'> element in domain config, unless explicitly enabled. <cpu mode='host-passthrough'> element may be used to configure other features, like NUMA, or CPUID. Also, adjust xenconfig driver to appropriately translate to/from nestedhvm=1. While at it, adjust xenconfig driver to not override def->cpu if already set elsewhere. This will help with adding cpuid support. --- As for xenconfig part, I'm not sure if missing "nestedhvm" option in xl config shouldn't produce <cpu> element too, to disable nested HVM (as it would be on plain xl). Any preference? Changes since v3: - use config option nested_hvm, instead of requiring explicit <feature ...> entries - title changed from "libxl: do not enable nested HVM by mere presence of <cpu> element" - xenconfig: don't add <feature policy='force' name='vmx'/> since it is implied by presence of <cpu> element - xenconfig: produce <cpu> element even when converting on host not supporting vmx/svm, to not lose setting value Changes since v2: - new patch --- src/libxl/libxl.conf | 6 ++++++- src/libxl/libxl_conf.c | 7 ++++++- src/libxl/libxl_conf.h | 2 ++- src/xenconfig/xen_xl.c | 37 +++++++++++------------------------ tests/libxlxml2domconfigtest.c | 3 +++- 5 files changed, 29 insertions(+), 26 deletions(-) diff --git a/src/libxl/libxl.conf b/src/libxl/libxl.conf index 264af7c..0e842c9 100644 --- a/src/libxl/libxl.conf +++ b/src/libxl/libxl.conf @@ -41,3 +41,9 @@ # #keepalive_interval = 5 #keepalive_count = 5 + +# Nested HVM global control. In order to use nested HVM feature, this option +# needs to be enabled, in addition to specifying <cpu mode='host-passthrough'> +# in domain configuration. +# By default it is disabled. +#nested_hvm = 0