On Thu, Apr 27, 2017 at 17:09:41 +0200, Peter Krempa wrote:
On Tue, Apr 25, 2017 at 20:48:45 +0200, Jiri Denemark wrote:
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
host-cache-info=on,l3-cache=off is specifically invalid from qemu's point of view?
No. Libvirt will automatically add l3-cache=off to host-cache-info=on and host-cache-info=off to l3-cache=on if it detects QEMU supports these properties. Otherwise it will just blindly add the one explicitly requested and let QEMU fail if it doesn't support it.
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@redhat.com> ---
[...]
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);
Is it really necessary to add both of them separately even if you set them both at once?
Hmm, I guess QEMU_CAPS_CPU_CACHE would be enough.
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 \
This is impossible in real life since QEMU_CAPS_CPU_HOST_CACHE and QEMU_CAPS_CPU_L3_CACHE are always defined together.
$cache=on is always added even if QEMU_CAPS_CPU_CACHE capability is not set. Only the $cache=off parameters are influenced by the capability. In other words, this is a real world command line generated for QEMU older than 2.9.0.
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);
This test is misleading, you don't get a config like this with this code.
Oh right, only QEMU_CAPS_KVM should be set for this test.
+ 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;
ACK with the above things sorted out.
Pushed with all the things sorted out. Thanks. Jirka