Re: [libvirt] [PATCH 3/3] qemu: Add support for guest CPU cache

This patch maps /domain/cpu/cache element into -cpu parameters: - <cache mode='passthrough'/> is translated to host-cache-info=on - <cache level='3' mode='emulate'/> is transformed into l3-cache=on - <cache mode='disable'/> is turned in host-cache-info=off,l3-cache=off

Any other <cache> element is forbidden. The tricky part is detecting whether QEMU supports the CPU properties. The 'host-cache-info' property is introduced in v2.4.0-1389-ge265e3e480, earlier QEMU releases enabled host-cache-info by default and had no way to disable it. If the property is present, it defaults to 'off' for any QEMU until at least 2.9.0. The 'l3-cache' property was introduced later by v2.7.0-200-g14c985cffa. Earlier versions worked as if l3-cache=off was passed. For any QEMU until at least 2.9.0 l3-cache is 'off' by default. QEMU 2.9.0 was the first release which supports probing both properties by running device-list-properties with typename=host-x86_64-cpu. Older QEMU releases did not support device-list-properties command for CPU devices. Thus we can't really rely on probing them and we can just use query-cpu-model-expansion QMP command as a witness. Because the cache property probing is only reliable for QEMU >= 2.9.0 when both are already supported for quite a few releases, we let QEMU report an error if a specific cache mode is explicitly requested. Thea other mode (or both if a user requested CPU cache to be disabled) is explicitly turned off for QEMU >= 2.9.0 to avoid any surprises in case the QEMU defaults change. Any older QEMU already turns them off so not doing so explicitly does not make any harm. Signed-off-by: Jiri Denemark <jdenemar(a)redhat.com&gt; ---

diff --git a/src/qemu/qemu_capabilities.c b/src/qemu/qemu_capabilities.c index cc3e1f808..5dd18f3c5 100644 --- a/src/qemu/qemu_capabilities.c +++ b/src/qemu/qemu_capabilities.c

@@ -4787,6 +4789,12 @@ virQEMUCapsInitQMPMonitor(virQEMUCapsPtr qemuCaps, virQEMUCapsGet(qemuCaps, QEMU_CAPS_DEVICE_NVDIMM)) virQEMUCapsClear(qemuCaps, QEMU_CAPS_DEVICE_NVDIMM); + if (ARCH_IS_X86(qemuCaps->arch) && + virQEMUCapsGet(qemuCaps, QEMU_CAPS_QUERY_CPU_MODEL_EXPANSION)) { + virQEMUCapsSet(qemuCaps, QEMU_CAPS_CPU_HOST_CACHE); + virQEMUCapsSet(qemuCaps, QEMU_CAPS_CPU_L3_CACHE);

+ } + ret = 0; cleanup: return ret;

diff --git a/src/qemu/qemu_command.c b/src/qemu/qemu_command.c index 1116d2cd5..eb7404ead 100644 --- a/src/qemu/qemu_command.c +++ b/src/qemu/qemu_command.c @@ -7063,6 +7063,43 @@ qemuBuildCpuCommandLine(virCommandPtr cmd, have_cpu = true; } + if (def->cpu && def->cpu->cache) { + virCPUCacheDefPtr cache = def->cpu->cache; + bool hostOff = false; + bool l3Off = false; + + if (!have_cpu) + virBufferAdd(&buf, default_model, -1);

+ + switch (cache->mode) { + case VIR_CPU_CACHE_MODE_EMULATE: + virBufferAddLit(&buf, ",l3-cache=on"); + hostOff = true; + break; + + case VIR_CPU_CACHE_MODE_PASSTHROUGH: + virBufferAddLit(&buf, ",host-cache-info=on"); + l3Off = true; + break; + + case VIR_CPU_CACHE_MODE_DISABLE: + hostOff = l3Off = true; + break; + + case VIR_CPU_CACHE_MODE_LAST: + break; + } + + if (hostOff && + def->cpu->mode == VIR_CPU_MODE_HOST_PASSTHROUGH && + virQEMUCapsGet(qemuCaps, QEMU_CAPS_CPU_HOST_CACHE)) + virBufferAddLit(&buf, ",host-cache-info=off"); + + if (l3Off && + virQEMUCapsGet(qemuCaps, QEMU_CAPS_CPU_L3_CACHE)) + virBufferAddLit(&buf, ",l3-cache=off"); + } + if (virBufferCheckError(&buf) < 0) goto cleanup;

diff --git a/tests/qemuxml2argvdata/qemuxml2argv-cpu-cache-passthrough2.args b/tests/qemuxml2argvdata/qemuxml2argv-cpu-cache-passthrough2.args new file mode 100644 index 000000000..cf4c55ca3 --- /dev/null +++ b/tests/qemuxml2argvdata/qemuxml2argv-cpu-cache-passthrough2.args @@ -0,0 +1,21 @@ +LC_ALL=C \ +PATH=/bin \ +HOME=/home/test \ +USER=test \ +LOGNAME=test \ +QEMU_AUDIO_DRV=none \ +/usr/bin/qemu-system-x86_64 \ +-name foo \ +-S \ +-M pc \ +-cpu host,host-cache-info=on \

+-m 214 \ +-smp 1,sockets=1,cores=1,threads=1 \ +-uuid c7a5fdbd-edaf-9455-926a-d65c16db1809 \ +-nographic \ +-nodefaults \ +-monitor unix:/tmp/lib/domain--1-foo/monitor.sock,server,nowait \ +-no-acpi \ +-boot c \ +-usb \ +-device virtio-balloon-pci,id=balloon0,bus=pci.0,addr=0x3

diff --git a/tests/qemuxml2argvtest.c b/tests/qemuxml2argvtest.c index c1b014b7d..15765fdfd 100644 --- a/tests/qemuxml2argvtest.c +++ b/tests/qemuxml2argvtest.c @@ -2513,6 +2513,22 @@ mymain(void) DO_TEST("cpu-check-default-partial", QEMU_CAPS_KVM); DO_TEST("cpu-check-default-partial2", QEMU_CAPS_KVM); + DO_TEST("cpu-cache-disable", + QEMU_CAPS_KVM, QEMU_CAPS_CPU_HOST_CACHE, QEMU_CAPS_CPU_L3_CACHE); + DO_TEST("cpu-cache-disable2", + QEMU_CAPS_KVM); + DO_TEST("cpu-cache-disable3", + QEMU_CAPS_KVM, QEMU_CAPS_CPU_HOST_CACHE, QEMU_CAPS_CPU_L3_CACHE); + DO_TEST("cpu-cache-passthrough", + QEMU_CAPS_KVM, QEMU_CAPS_CPU_HOST_CACHE, QEMU_CAPS_CPU_L3_CACHE); + DO_TEST("cpu-cache-passthrough2", + QEMU_CAPS_KVM, QEMU_CAPS_CPU_HOST_CACHE);

+ DO_TEST("cpu-cache-emulate-l3", + QEMU_CAPS_KVM, QEMU_CAPS_CPU_HOST_CACHE, QEMU_CAPS_CPU_L3_CACHE); + DO_TEST_PARSE_ERROR("cpu-cache-emulate-l2", QEMU_CAPS_KVM); + DO_TEST_PARSE_ERROR("cpu-cache-passthrough3", QEMU_CAPS_KVM); + DO_TEST_PARSE_ERROR("cpu-cache-passthrough-l3", QEMU_CAPS_KVM); + qemuTestDriverFree(&driver); return ret == 0 ? EXIT_SUCCESS : EXIT_FAILURE;