From: Sandesh Patel <sandesh.patel@nutanix.com> Hi, This RFC series adds libvirt support for ARM CPU features that are exposed by QEMU as multi-valued properties, rather than the on/off booleans we are used to from x86. Background ========== On ARM, several CPU properties can take one of a small set of values (e.g. "0.0", "1.0", "1.1_base", "off"), and the set of values supported by each property is host-specific. This cannot be expressed using libvirt's existing boolean feature model. This series depends on a pending QEMU RFC [1] that introduces non-boolean feature handling for ARM CPUs. That series also adds a new QMP command, query-arm-cpu-props-info, which reports the values the host accelerator supports for each ARM CPU property. Example reply fragment: { "name": "hw_prop_WRPs", "supported-values": ["0-3"], "type": "number" } On top of that QEMU work, this libvirt RFC wires up the end-to-end flow: probing the host, caching the probed information, exposing the values in the guest CPU XML, and passing them through to the QEMU -cpu command line. I am posting this as an RFC primarily to get maintainer feedback on the overall approach before investing in the missing pieces (in particular, value validation, which is intentionally not yet implemented). See "Open questions" below. Overview of the series ====================== 1. Add a QMP wrapper for query-arm-cpu-props-info, a new QEMU_CAPS_QUERY_ARM_CPU_PROPS_INFO capability bit, and the qemuMonitorCPUPropsInfoList data structure. The command is issued on ARM + KVM hosts and the reply is stored in the per-accelerator capabilities. 2. Persist the probed list into the on-disk QEMU capabilities cache as <cpuPropertyInfo>, so that subsequent libvirtd restarts do not need to re-issue the QMP query. 3. Extend the guest CPU XML with an optional 'value' attribute on <feature>: <cpu mode='host-passthrough'> <feature policy='require' name='feat_RAS' value='1.0'/> <feature policy='require' name='hw_prop_API' value='off'/> <feature policy='require' name='hw_prop_WRPs' value='2'/> </cpu> When a feature carries a non-NULL 'value', libvirt emits '<name>=<value>' on the QEMU -cpu command line; in that case the policy must be 'require' or 'force'. The existing policy-driven '=on' / '=off' path is used only for features without an explicit value. All ARM property names returned by query-arm-cpu-props-info are registered in src/cpu_map/arm_features.xml so that the guest XML parser and validator accept them. With this change, the generated QEMU command line can look like: -cpu host-passthrough,hw_prop_API=off,hw_prop_WRPs=2 Changes since v1: ================ - Split the single "query" patch so the new capability bit is added in its own patch, separate from the code that uses it. - The capability dump is now captured from a real QEMU (built with the pending ARM series and probed with qemucapsprobe on a KVM host) instead of being edited by hand. It is added as a separate "+armcpuprops" variant Open questions ============== - Value validation: should libvirt validate the requested value against the host's supported-values list at define time, at start time, or defer entirely to QEMU? - Policy vs. value conflicts: is requiring policy='require' / 'force' whenever 'value' is set the right rule? - Caching location: is the per-accelerator QEMU capabilities cache the right place to store the probed property list, or should this live alongside the CPU model data in cpu_map? Sandesh Patel (5): Add QEMU_CAPS_QUERY_ARM_CPU_PROPS_INFO Add support to query ARM CPU property values Cache and load ARM CPU property information Add '+armcpuprops' capability variant for query-arm-cpu-props-info QMP Support 'value' attribute on CPU features src/conf/cpu_conf.c | 21 +- src/conf/cpu_conf.h | 1 + src/conf/schemas/cputypes.rng | 5 + src/cpu_map/arm_features.xml | 171 + src/qemu/qemu_capabilities.c | 130 +- src/qemu/qemu_capabilities.h | 1 + src/qemu/qemu_command.c | 13 + src/qemu/qemu_monitor.c | 52 + src/qemu/qemu_monitor.h | 26 + src/qemu/qemu_monitor_json.c | 66 + src/qemu/qemu_monitor_json.h | 5 + .../qemu_11.1.0-virt.aarch64+armcpuprops.xml | 357 + .../qemu_11.1.0.aarch64+armcpuprops.xml | 357 + .../caps_11.1.0_aarch64+armcpuprops.replies | 40506 ++++++++++++++++ .../caps_11.1.0_aarch64+armcpuprops.xml | 1436 + .../caps.aarch64+armcpuprops.xml | 28 + tests/qemumonitorjsontest.c | 91 + ...res-values.aarch64-latest+armcpuprops.args | 34 + ...ures-values.aarch64-latest+armcpuprops.xml | 46 + .../aarch64-cpu-features-values.xml | 30 + tests/qemuxmlconftest.c | 2 + tests/testutilshostcpus.h | 74 +- 22 files changed, 43411 insertions(+), 41 deletions(-) create mode 100644 tests/domaincapsdata/qemu_11.1.0-virt.aarch64+armcpuprops.xml create mode 100644 tests/domaincapsdata/qemu_11.1.0.aarch64+armcpuprops.xml create mode 100644 tests/qemucapabilitiesdata/caps_11.1.0_aarch64+armcpuprops.replies create mode 100644 tests/qemucapabilitiesdata/caps_11.1.0_aarch64+armcpuprops.xml create mode 100644 tests/qemucaps2xmloutdata/caps.aarch64+armcpuprops.xml create mode 100644 tests/qemuxmlconfdata/aarch64-cpu-features-values.aarch64-latest+armcpuprops.args create mode 100644 tests/qemuxmlconfdata/aarch64-cpu-features-values.aarch64-latest+armcpuprops.xml create mode 100644 tests/qemuxmlconfdata/aarch64-cpu-features-values.xml -- 2.43.7