| Message ID | 1470623282-3837-1-git-send-email-douly.fnst@cn.fujitsu.com (mailing list archive) |
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On Mon, 8 Aug 2016 10:28:02 +0800 Dou Liyang <douly.fnst@cn.fujitsu.com> wrote: > This document describes how to use cpu hotplug in QEMU. > > Signed-off-by: Dou Liyang <douly.fnst@cn.fujitsu.com> > --- > docs/cpu-hotplug.txt | 110 +++++++++++++++++++++++++++++++++++++++++++++++++++ > 1 file changed, 110 insertions(+) > create mode 100644 docs/cpu-hotplug.txt > > diff --git a/docs/cpu-hotplug.txt b/docs/cpu-hotplug.txt > new file mode 100644 > index 0000000..d62638e > --- /dev/null > +++ b/docs/cpu-hotplug.txt > @@ -0,0 +1,110 @@ > +QEMU CPU hotplug > +=================== > + > +This document explains how to use the cpu hotplug feature in QEMU, > +which is present since v2.6.0. -device/device_add based CPUs are merged since 2.7 > + > +Guest support is required for cpu hotplug to work. > + > +CPU hotplug > +------------------- > + > +In order to be able to hotplug cpu, QEMU has to be told what is the > +maximum amount of cpus the guest can grow. This is done at startup > +time by means of the -smp command-line option, which has the following > +format: > + > + -smp [cpus=]n[,maxcpus=cpus][,cores=cores][,threads=threads] > + [,sockets=sockets] > + > +Where, > + > + - "cpus" set the number of CPUs to 'n' [default=1] > + - "maxcpus" maximum number of total cpus, including offlineCPUs for > + hotplug, etc s/total// s/offlineCPUs/offline VCPUs/ or threads > + - "cores" number of CPU cores on one socket > + - "threads= number of threads on one CPU core > + - "sockets= number of discrete sockets in the system Above needs additional meaning clarification for SPAPR, CCing David > + > + > +For example, the following command-line: > + > + qemu [...] -smp 3,maxcpus=10,sockets=2,cores=2,threads=2 > + > +Creates a guest with 3 cpus and it support up to 10 cpus. The cpu > +topology is sockets (2) * cores (2) * threads (2) and can't greater > +than maxcpus. When the guest is just booted, the guest will see 3 > +cpus. so there are seven cpus can be hotplugged by using any > +combination of the available sockets,cores and threads topology or > +using apic-id. s/cpus/vcpus/ drop any mentioning of apic-id, it's not supposed to be used by user and socket/core/thread-ids should be used i.e. properties advertised by QEMU via QMP command query-hotpluggable-cpus or corresponding HMP command 'info hotpluggable-cpus' PS: Eduardo should we drop apic-id property before 2.7 is released? So people won't even try to use it, it wan never a public property before as cpus weren't available with -device/device_add. > +cpu hot-plug > +----------------------- > + > +A monitor commands are used to hotplug cpu: > + > + - "device_add": creates a cpu device and inserts it into the > + specific topology as a device > + > +For example, the following commands add a cpu which id is cpu1 to > +the guest discussed earlier: > + > + (qemu) device_add qemu64-x86_64-cpu,id=cpu1,apic-id=3 likewise remove any mentioning of apic-id from document I'd add as the first section here commands that query possible available cpus including topology properties. > + > + - "qemu64-x86_64-cpu" is the cpu modle. > + - "id" is the unique identifier in the device sets. > + - "apic-id" is the hotpluged cpu's physical identification. > + > +Another command uses the cpu topology to add the additional cpu in > +the designated position. > + > +For example, the following commands add a cpu in the last position > +of the guest cpu topology discussed earlier. > + > + (qemu) device_add qemu64-x86_64-cpu,id=cpu1,socket-id=2,core-id=1, > + thread-id=1 > + > +It's also possible to start a guest with cpu cold-plugged into the > +hotpluggable cpu topology. s/hotpluggable cpu topology/specific place (socket,core,thread)/ > + > +In the following command-line example, a guest which has 3 cpus is > +created where one of the cpus comes from the "apic-id", and another > +one comes from "socket-id...". After that, the guest has additional > +seven cpus to be hot-plug when needed: > + > + qemu [...] -smp 1,maxcpus=10,sockets=2,cores=2,threads=2 > + -device qemu64-x86_64-cpu,id=cpu1,apic-id=1 > + -device qemu64-x86_64-cpu,socket-id=2,core-id=1,thread-id=0 > + > +cpu hot-unplug > +------------------------ > + > +In order to be able to hot unplug cpu device, QEMU has two ways > +to remove cpu device. > + 1. Using the ids which were assigned when you hot plugged cpus. > + 2. Using qom_path where the cpu is located in the guest. I wouldn't advertise #2 as it's possible to unplug CPUs created with -smp X with its help and then have broken migration device_del qom_path should even be able to remove a device without ID, it should allow removal of devices below /machine/peripheral only instead of current anywhere. Daniel, is it a bug in current device_del impl.? i.e. device_del /machine/unattached/device[2] is currently allowed while I think it shouldn't. > + > +A monitor commands are used to hot unplug cpus: > + > + - "device_del": deletes a cpu device > + > +For example, assuming that the cpu device with id "cpu1" exists, > +the following commands tries to remove it. > + > + (qemu) device_del cpu1 > + > +If you don't set the ids when you hot plugged cpus. > + > +First, you may need to obtain the cpu's qom_path. The following > +commands list all hotplugable-cpus, you can get the qom_path > +through the cpu topology. > + > + (qemu) info hotpluggable-cpus > + > +Then you can remove it by the qom_path. > + > +For example, assuming that the cpu device with qom_path "/machine > +/unattached/device[0]" exists, the following commands tries to > +remove it. > + > + (qemu) device_del /machine/unattached/device[0] I'd remove qom-path related parts and leave only ID based one.
On Mon, Aug 08, 2016 at 02:18:05PM +0200, Igor Mammedov wrote: [...] > PS: > Eduardo should we drop apic-id property before 2.7 is released? > So people won't even try to use it, it wan never a public > property before as cpus weren't available with -device/device_add. If it is never supposed to be set by the user, we could keep it and make it read-only. It is helpful for debugging, and it is probably the most reliable way to map the host-side CPU objects to the IDs seen by the guest.
On Mon, Aug 08, 2016 at 02:18:05PM +0200, Igor Mammedov wrote: > On Mon, 8 Aug 2016 10:28:02 +0800 > Dou Liyang <douly.fnst@cn.fujitsu.com> wrote: > > > This document describes how to use cpu hotplug in QEMU. > > > > Signed-off-by: Dou Liyang <douly.fnst@cn.fujitsu.com> > > --- > > docs/cpu-hotplug.txt | 110 +++++++++++++++++++++++++++++++++++++++++++++++++++ > > 1 file changed, 110 insertions(+) > > create mode 100644 docs/cpu-hotplug.txt > > > > diff --git a/docs/cpu-hotplug.txt b/docs/cpu-hotplug.txt > > new file mode 100644 > > index 0000000..d62638e > > --- /dev/null > > +++ b/docs/cpu-hotplug.txt > > @@ -0,0 +1,110 @@ > > +QEMU CPU hotplug > > +=================== > > + > > +This document explains how to use the cpu hotplug feature in QEMU, > > +which is present since v2.6.0. > > -device/device_add based CPUs are merged since 2.7 > > > + > > +Guest support is required for cpu hotplug to work. > > + > > +CPU hotplug > > +------------------- > > + > > +In order to be able to hotplug cpu, QEMU has to be told what is the > > +maximum amount of cpus the guest can grow. This is done at startup > > +time by means of the -smp command-line option, which has the following > > +format: > > + > > + -smp [cpus=]n[,maxcpus=cpus][,cores=cores][,threads=threads] > > + [,sockets=sockets] > > + > > +Where, > > + > > + - "cpus" set the number of CPUs to 'n' [default=1] > > + - "maxcpus" maximum number of total cpus, including offlineCPUs for > > + hotplug, etc > s/total// > s/offlineCPUs/offline VCPUs/ or threads > > > + - "cores" number of CPU cores on one socket > > + - "threads= number of threads on one CPU core > > + - "sockets= number of discrete sockets in the system > Above needs additional meaning clarification for SPAPR, > CCing David Sockets have no real meaning on sPAPR. You can decide how many cores go into each "socket", but it has no real effect on the guest. > > > + > > + > > +For example, the following command-line: > > + > > + qemu [...] -smp 3,maxcpus=10,sockets=2,cores=2,threads=2 > > + > > +Creates a guest with 3 cpus and it support up to 10 cpus. The cpu > > +topology is sockets (2) * cores (2) * threads (2) and can't greater > > +than maxcpus. When the guest is just booted, the guest will see 3 > > +cpus. so there are seven cpus can be hotplugged by using any > > +combination of the available sockets,cores and threads topology or > > +using apic-id. > s/cpus/vcpus/ > > drop any mentioning of apic-id, it's not supposed to be used > by user and socket/core/thread-ids should be used i.e. > properties advertised by QEMU via QMP command query-hotpluggable-cpus > or corresponding HMP command 'info hotpluggable-cpus' > > PS: > Eduardo should we drop apic-id property before 2.7 is released? > So people won't even try to use it, it wan never a public > property before as cpus weren't available with -device/device_add. > > > > +cpu hot-plug > > +----------------------- > > + > > +A monitor commands are used to hotplug cpu: > > + > > + - "device_add": creates a cpu device and inserts it into the > > + specific topology as a device > > + > > +For example, the following commands add a cpu which id is cpu1 to > > +the guest discussed earlier: > > + > > + (qemu) device_add qemu64-x86_64-cpu,id=cpu1,apic-id=3 > likewise remove any mentioning of apic-id from document > > I'd add as the first section here commands that query possible > available cpus including topology properties. > > > + > > + - "qemu64-x86_64-cpu" is the cpu modle. > > + - "id" is the unique identifier in the device sets. > > + - "apic-id" is the hotpluged cpu's physical identification. > > + > > +Another command uses the cpu topology to add the additional cpu in > > +the designated position. > > + > > +For example, the following commands add a cpu in the last position > > +of the guest cpu topology discussed earlier. > > + > > + (qemu) device_add qemu64-x86_64-cpu,id=cpu1,socket-id=2,core-id=1, > > + thread-id=1 > > + > > +It's also possible to start a guest with cpu cold-plugged into the > > +hotpluggable cpu topology. > s/hotpluggable cpu topology/specific place (socket,core,thread)/ > > > + > > +In the following command-line example, a guest which has 3 cpus is > > +created where one of the cpus comes from the "apic-id", and another > > +one comes from "socket-id...". After that, the guest has additional > > +seven cpus to be hot-plug when needed: > > + > > + qemu [...] -smp 1,maxcpus=10,sockets=2,cores=2,threads=2 > > + -device qemu64-x86_64-cpu,id=cpu1,apic-id=1 > > + -device qemu64-x86_64-cpu,socket-id=2,core-id=1,thread-id=0 > > + > > +cpu hot-unplug > > +------------------------ > > + > > +In order to be able to hot unplug cpu device, QEMU has two ways > > +to remove cpu device. > > + 1. Using the ids which were assigned when you hot plugged cpus. > > + 2. Using qom_path where the cpu is located in the guest. > I wouldn't advertise #2 as it's possible to unplug CPUs created with > -smp X with its help and then have broken migration > > device_del qom_path should even be able to remove a device without ID, > it should allow removal of devices below /machine/peripheral only > instead of current anywhere. > > Daniel, > is it a bug in current device_del impl.? > i.e. device_del /machine/unattached/device[2] > is currently allowed while I think it shouldn't. > > > + > > +A monitor commands are used to hot unplug cpus: > > + > > + - "device_del": deletes a cpu device > > + > > +For example, assuming that the cpu device with id "cpu1" exists, > > +the following commands tries to remove it. > > + > > + (qemu) device_del cpu1 > > + > > +If you don't set the ids when you hot plugged cpus. > > + > > > > +First, you may need to obtain the cpu's qom_path. The following > > +commands list all hotplugable-cpus, you can get the qom_path > > +through the cpu topology. > > + > > + (qemu) info hotpluggable-cpus > > + > > +Then you can remove it by the qom_path. > > + > > +For example, assuming that the cpu device with qom_path "/machine > > +/unattached/device[0]" exists, the following commands tries to > > +remove it. > > + > > + (qemu) device_del /machine/unattached/device[0] > I'd remove qom-path related parts and leave only ID based one. >
On Mon, Aug 08, 2016 at 10:28:02AM +0800, Dou Liyang wrote: > This document describes how to use cpu hotplug in QEMU. > > Signed-off-by: Dou Liyang <douly.fnst@cn.fujitsu.com> > --- > docs/cpu-hotplug.txt | 110 +++++++++++++++++++++++++++++++++++++++++++++++++++ > 1 file changed, 110 insertions(+) > create mode 100644 docs/cpu-hotplug.txt > > diff --git a/docs/cpu-hotplug.txt b/docs/cpu-hotplug.txt > new file mode 100644 > index 0000000..d62638e > --- /dev/null > +++ b/docs/cpu-hotplug.txt > @@ -0,0 +1,110 @@ > +QEMU CPU hotplug > +=================== > + > +This document explains how to use the cpu hotplug feature in QEMU, > +which is present since v2.6.0. > + > +Guest support is required for cpu hotplug to work. > + > +CPU hotplug > +------------------- > + > +In order to be able to hotplug cpu, QEMU has to be told what is the a cpu > +maximum amount of cpus the guest can grow. This is done at startup /grow/have/ > +time by means of the -smp command-line option, which has the following > +format: > + > + -smp [cpus=]n[,maxcpus=cpus][,cores=cores][,threads=threads] > + [,sockets=sockets] > + > +Where, > + > + - "cpus" set the number of CPUs to 'n' [default=1] /set/sets/ > + - "maxcpus" maximum number of total cpus, including offlineCPUs for is the maximum... remove the word 'total' > + hotplug, etc > + - "cores" number of CPU cores on one socket is the number > + - "threads= number of threads on one CPU core is the number > + - "sockets= number of discrete sockets in the system is the number > + > + > +For example, the following command-line: > + > + qemu [...] -smp 3,maxcpus=10,sockets=2,cores=2,threads=2 > + > +Creates a guest with 3 cpus and it support up to 10 cpus. The cpu /it support/supports/ > +topology is sockets (2) * cores (2) * threads (2) and can't greater > +than maxcpus. The topology should exactly provide maxcpus, i.e. this example is wrong because the topology only provides a maximum of 8 cpus, but maxcpus=10. Indeed specifying maxcpus is redundant when a complete topology is given. > When the guest is just booted, the guest will see 3 ^^ it > +cpus. so there are seven cpus can be hotplugged by using any Five cpus may be hotplugged using any ... > +combination of the available sockets,cores and threads topology or sockets, cores, and threads I'm not sure what the "using any combination..." means though. > +using apic-id. by using > + > +cpu hot-plug > +----------------------- > + > +A monitor commands are used to hotplug cpu: /A monitor/Monitor/ /cpu/cpus/ > + > + - "device_add": creates a cpu device and inserts it into the > + specific topology as a device > + > +For example, the following commands add a cpu which id is cpu1 to /commands add/command adds/ > +the guest discussed earlier: a guest: > + > + (qemu) device_add qemu64-x86_64-cpu,id=cpu1,apic-id=3 > + > + - "qemu64-x86_64-cpu" is the cpu modle. /modle/model/ > + - "id" is the unique identifier in the device sets. /sets/set/ > + - "apic-id" is the hotpluged cpu's physical identification. > + > +Another command uses the cpu topology to add the additional cpu in /the cpu topology/cpu topology/ > +the designated position. > + > +For example, the following commands add a cpu in the last position > +of the guest cpu topology discussed earlier. command adds a cpu to position socket=2, core=1, thread=1: > + > + (qemu) device_add qemu64-x86_64-cpu,id=cpu1,socket-id=2,core-id=1, > + thread-id=1 > + > +It's also possible to start a guest with cpu cold-plugged into the with a cpu > +hotpluggable cpu topology. > + > +In the following command-line example, a guest which has 3 cpus is > +created where one of the cpus comes from the "apic-id", and another > +one comes from "socket-id...". After that, the guest has additional > +seven cpus to be hot-plug when needed: > + > + qemu [...] -smp 1,maxcpus=10,sockets=2,cores=2,threads=2 Broken example again; 2*2*2 != 10 > + -device qemu64-x86_64-cpu,id=cpu1,apic-id=1 > + -device qemu64-x86_64-cpu,socket-id=2,core-id=1,thread-id=0 > + > +cpu hot-unplug > +------------------------ > + > +In order to be able to hot unplug cpu device, QEMU has two ways > +to remove cpu device. a cpu device /ways to remove cpu device/methods of removal;/ > + 1. Using the ids which were assigned when you hot plugged cpus. s/you hot plugged/hotplugging/ > + 2. Using qom_path where the cpu is located in the guest. Using the qom_path of the cpu. > + > +A monitor commands are used to hot unplug cpus: /Monitor commands/ > + > + - "device_del": deletes a cpu device > + > +For example, assuming that the cpu device with id "cpu1" exists, > +the following commands tries to remove it. /commands/command/ /./:/ > + > + (qemu) device_del cpu1 > + > +If you don't set the ids when you hot plugged cpus. > + > +First, you may need to obtain the cpu's qom_path. The following If the IDs are not set when hotplugging, then the cpu's qom_path needs to be obtained. > +commands list all hotplugable-cpus, you can get the qom_path > +through the cpu topology. /commands list/command lists/ > + > + (qemu) info hotpluggable-cpus > + > +Then you can remove it by the qom_path. Drop this sentence. > + > +For example, assuming that the cpu device with qom_path "/machine > +/unattached/device[0]" exists, the following commands tries to /commands/command/ > +remove it. > + > + (qemu) device_del /machine/unattached/device[0] > -- > 2.5.5 > > > > Thanks, drew
diff --git a/docs/cpu-hotplug.txt b/docs/cpu-hotplug.txt new file mode 100644 index 0000000..d62638e --- /dev/null +++ b/docs/cpu-hotplug.txt @@ -0,0 +1,110 @@ +QEMU CPU hotplug +=================== + +This document explains how to use the cpu hotplug feature in QEMU, +which is present since v2.6.0. + +Guest support is required for cpu hotplug to work. + +CPU hotplug +------------------- + +In order to be able to hotplug cpu, QEMU has to be told what is the +maximum amount of cpus the guest can grow. This is done at startup +time by means of the -smp command-line option, which has the following +format: + + -smp [cpus=]n[,maxcpus=cpus][,cores=cores][,threads=threads] + [,sockets=sockets] + +Where, + + - "cpus" set the number of CPUs to 'n' [default=1] + - "maxcpus" maximum number of total cpus, including offlineCPUs for + hotplug, etc + - "cores" number of CPU cores on one socket + - "threads= number of threads on one CPU core + - "sockets= number of discrete sockets in the system + + +For example, the following command-line: + + qemu [...] -smp 3,maxcpus=10,sockets=2,cores=2,threads=2 + +Creates a guest with 3 cpus and it support up to 10 cpus. The cpu +topology is sockets (2) * cores (2) * threads (2) and can't greater +than maxcpus. When the guest is just booted, the guest will see 3 +cpus. so there are seven cpus can be hotplugged by using any +combination of the available sockets,cores and threads topology or +using apic-id. + +cpu hot-plug +----------------------- + +A monitor commands are used to hotplug cpu: + + - "device_add": creates a cpu device and inserts it into the + specific topology as a device + +For example, the following commands add a cpu which id is cpu1 to +the guest discussed earlier: + + (qemu) device_add qemu64-x86_64-cpu,id=cpu1,apic-id=3 + + - "qemu64-x86_64-cpu" is the cpu modle. + - "id" is the unique identifier in the device sets. + - "apic-id" is the hotpluged cpu's physical identification. + +Another command uses the cpu topology to add the additional cpu in +the designated position. + +For example, the following commands add a cpu in the last position +of the guest cpu topology discussed earlier. + + (qemu) device_add qemu64-x86_64-cpu,id=cpu1,socket-id=2,core-id=1, + thread-id=1 + +It's also possible to start a guest with cpu cold-plugged into the +hotpluggable cpu topology. + +In the following command-line example, a guest which has 3 cpus is +created where one of the cpus comes from the "apic-id", and another +one comes from "socket-id...". After that, the guest has additional +seven cpus to be hot-plug when needed: + + qemu [...] -smp 1,maxcpus=10,sockets=2,cores=2,threads=2 + -device qemu64-x86_64-cpu,id=cpu1,apic-id=1 + -device qemu64-x86_64-cpu,socket-id=2,core-id=1,thread-id=0 + +cpu hot-unplug +------------------------ + +In order to be able to hot unplug cpu device, QEMU has two ways +to remove cpu device. + 1. Using the ids which were assigned when you hot plugged cpus. + 2. Using qom_path where the cpu is located in the guest. + +A monitor commands are used to hot unplug cpus: + + - "device_del": deletes a cpu device + +For example, assuming that the cpu device with id "cpu1" exists, +the following commands tries to remove it. + + (qemu) device_del cpu1 + +If you don't set the ids when you hot plugged cpus. + +First, you may need to obtain the cpu's qom_path. The following +commands list all hotplugable-cpus, you can get the qom_path +through the cpu topology. + + (qemu) info hotpluggable-cpus + +Then you can remove it by the qom_path. + +For example, assuming that the cpu device with qom_path "/machine +/unattached/device[0]" exists, the following commands tries to +remove it. + + (qemu) device_del /machine/unattached/device[0]
This document describes how to use cpu hotplug in QEMU. Signed-off-by: Dou Liyang <douly.fnst@cn.fujitsu.com> --- docs/cpu-hotplug.txt | 110 +++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 110 insertions(+) create mode 100644 docs/cpu-hotplug.txt