On Thu, Nov 04, 2021 at 01:22:53PM +0100, Michal Privoznik wrote: > 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@xxxxxxxxxx> > --- > src/qemu/qemu_command.c | 14 ++++++- > ...efault-cpu-tcg-features.x86_64-latest.args | 40 +++++++++++++++++++ > tests/qemuxml2argvtest.c | 1 + > 3 files changed, 54 insertions(+), 1 deletion(-) > 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 45278c7108..7d9cb386fd 100644 > --- a/src/qemu/qemu_command.c > +++ b/src/qemu/qemu_command.c > @@ -7031,14 +7031,21 @@ qemuBuildMachineCommandLine(virCommand *cmd, > virTristateSwitch smm = def->features[VIR_DOMAIN_FEATURE_SMM]; > virCPUDef *cpu = def->cpu; > g_auto(virBuffer) buf = VIR_BUFFER_INITIALIZER; > + unsigned long long tb_cache = 0; > size_t i; > > + if (def->features[VIR_DOMAIN_FEATURE_TCG] == VIR_TRISTATE_SWITCH_ON) > + tb_cache = def->tcg_features->tb_cache; > + > virCommandAddArg(cmd, "-machine"); > virBufferAdd(&buf, def->os.machine, -1); > > switch ((virDomainVirtType)def->virtType) { > case VIR_DOMAIN_VIRT_QEMU: > - virBufferAddLit(&buf, ",accel=tcg"); > + /* Unfortunately, -machine doesn't accept -accel arguments and the two > + * are mutually exclusive. Don't output accel= if we need -accel. */ > + if (tb_cache == 0) > + virBufferAddLit(&buf, ",accel=tcg"); The "-machine accel=nnn" syntax was the original way to configure accelerator. The "-accel nnn,$opts" syntax was added in QEMU 2.9.0 with commit 8d4e9146b3568022ea5730d92841345d41275d66 Author: KONRAD Frederic <fred.konrad@xxxxxxxxxxxxx> Date: Thu Feb 23 18:29:08 2017 +0000 tcg: add options for enabling MTTCG with the accelerator name being sugar for "-machine accel=nnn". Then in 5.0.0, this was reversed so that '-machine accel=nnn' is now sugar for '-accel nnn' commit 6f6e1698a68ceb49e57676528612f22eaf2c16c3 Author: Paolo Bonzini <pbonzini@xxxxxxxxxx> Date: Wed Nov 13 10:10:47 2019 +0100 vl: configure accelerators from -accel options IOW, long term we want to be using -accel exclusively. Given our minimum QEMU 2.11.0, we can in fact use -accel exclusively already AFAICT. That would simplify this patch so that we're not supporting distinct syntax with tb_cache. > break; > > case VIR_DOMAIN_VIRT_KVM: > @@ -7288,6 +7295,11 @@ qemuBuildMachineCommandLine(virCommand *cmd, > > virCommandAddArgBuffer(cmd, &buf); > > + if (tb_cache > 0) { > + virCommandAddArg(cmd, "-accel"); > + virCommandAddArgFormat(cmd, "tcg,tb-size=%llu", tb_cache >> 10); > + } > + > return 0; > } > > diff --git a/tests/qemuxml2argvdata/x86_64-default-cpu-tcg-features.x86_64-latest.args b/tests/qemuxml2argvdata/x86_64-default-cpu-tcg-features.x86_64-latest.args > new file mode 100644 > index 0000000000..0800ea4294 > --- /dev/null > +++ b/tests/qemuxml2argvdata/x86_64-default-cpu-tcg-features.x86_64-latest.args > @@ -0,0 +1,40 @@ > +LC_ALL=C \ > +PATH=/bin \ > +HOME=/tmp/lib/domain--1-guest \ > +USER=test \ > +LOGNAME=test \ > +XDG_DATA_HOME=/tmp/lib/domain--1-guest/.local/share \ > +XDG_CACHE_HOME=/tmp/lib/domain--1-guest/.cache \ > +XDG_CONFIG_HOME=/tmp/lib/domain--1-guest/.config \ > +/usr/bin/qemu-system-x86_64 \ > +-name guest=guest,debug-threads=on \ > +-S \ > +-object '{"qom-type":"secret","id":"masterKey0","format":"raw","file":"/tmp/lib/domain--1-guest/master-key.aes"}' \ > +-machine pc-q35-6.2,usb=off,dump-guest-core=off,memory-backend=pc.ram \ > +-accel tcg,tb-size=100 \ > +-cpu qemu64 \ > +-m 4096 \ > +-object '{"qom-type":"memory-backend-ram","id":"pc.ram","size":4294967296}' \ > +-overcommit mem-lock=off \ > +-smp 4,sockets=4,cores=1,threads=1 \ > +-uuid 1ccfd97d-5eb4-478a-bbe6-88d254c16db7 \ > +-display none \ > +-no-user-config \ > +-nodefaults \ > +-chardev socket,id=charmonitor,fd=1729,server=on,wait=off \ > +-mon chardev=charmonitor,id=monitor,mode=control \ > +-rtc base=utc \ > +-no-shutdown \ > +-boot strict=on \ > +-device '{"driver":"pcie-root-port","port":8,"chassis":1,"id":"pci.1","bus":"pcie.0","multifunction":true,"addr":"0x1"}' \ > +-device '{"driver":"pcie-root-port","port":9,"chassis":2,"id":"pci.2","bus":"pcie.0","addr":"0x1.0x1"}' \ > +-device '{"driver":"pcie-root-port","port":10,"chassis":3,"id":"pci.3","bus":"pcie.0","addr":"0x1.0x2"}' \ > +-device '{"driver":"pcie-root-port","port":11,"chassis":4,"id":"pci.4","bus":"pcie.0","addr":"0x1.0x3"}' \ > +-device '{"driver":"qemu-xhci","id":"usb","bus":"pci.1","addr":"0x0"}' \ > +-blockdev '{"driver":"file","filename":"/var/lib/libvirt/images/guest.qcow2","node-name":"libvirt-1-storage","auto-read-only":true,"discard":"unmap"}' \ > +-blockdev '{"node-name":"libvirt-1-format","read-only":false,"driver":"qcow2","file":"libvirt-1-storage"}' \ > +-device '{"driver":"virtio-blk-pci","bus":"pci.2","addr":"0x0","drive":"libvirt-1-format","id":"virtio-disk0","bootindex":1}' \ > +-audiodev id=audio1,driver=none \ > +-device '{"driver":"virtio-balloon-pci","id":"balloon0","bus":"pci.3","addr":"0x0"}' \ > +-sandbox on,obsolete=deny,elevateprivileges=deny,spawn=deny,resourcecontrol=deny \ > +-msg timestamp=on > diff --git a/tests/qemuxml2argvtest.c b/tests/qemuxml2argvtest.c > index 1c59395203..56ecc46071 100644 > --- a/tests/qemuxml2argvtest.c > +++ b/tests/qemuxml2argvtest.c > @@ -3422,6 +3422,7 @@ mymain(void) > DO_TEST_CAPS_ARCH_LATEST("x86_64-default-cpu-tcg-pc-4.2", "x86_64"); > DO_TEST_CAPS_ARCH_LATEST("x86_64-default-cpu-kvm-q35-4.2", "x86_64"); > DO_TEST_CAPS_ARCH_LATEST("x86_64-default-cpu-tcg-q35-4.2", "x86_64"); > + DO_TEST_CAPS_ARCH_LATEST("x86_64-default-cpu-tcg-features", "x86_64"); > > DO_TEST_CAPS_LATEST("virtio-9p-multidevs"); > DO_TEST_CAPS_LATEST("virtio-9p-createmode"); > -- > 2.32.0 > Regards, Daniel -- |: https://berrange.com -o- https://www.flickr.com/photos/dberrange :| |: https://libvirt.org -o- https://fstop138.berrange.com :| |: https://entangle-photo.org -o- https://www.instagram.com/dberrange :|
