Re: [Xen-devel] [libvirt] [PATCH V2] Xen: support maxvcpus in xm and xl config

[Jim Fehlig <jfehlig@xxxxxxxx>]

On 12/18/2015 04:47 AM, Michal Privoznik wrote:
> On 15.12.2015 23:20, Jim Fehlig wrote:
>> From: Ian Campbell <ian.campbell@xxxxxxxxxx>
>>
>> xend prior to 4.0 understands vcpus as maxvcpus and vcpu_avail
>> as a bit map of which cpus are online (default is all).
>>
>> xend from 4.0 onwards understands maxvcpus as maxvcpus and
>> vcpus as the number which are online (from 0..N-1). The
>> upstream commit (68a94cf528e6 "xm: Add maxvcpus support")
>> claims that if maxvcpus is omitted then the old behaviour
>> (i.e. obeying vcpu_avail) is retained, but AFAICT it was not,
>> in this case vcpu==maxcpus==online cpus. This is good for us
>> because handling anything else would be fiddly.
>>
>> This patch changes parsing of the virDomainDef maxvcpus and vcpus
>> entries to use the corresponding 'maxvcpus' and 'vcpus' settings
>> from xm and xl config. It also drops use of the old Xen 3.x
>> 'vcpu_avail' setting.
>>
>> The change also removes the maxvcpus limit of MAX_VIRT_VCPUS (since
>> maxvcpus is simply a count, not a bit mask), which is particularly
>> crucial on ARM where MAX_VIRT_CPUS == 1 (since all guests are
>> expected to support vcpu placement, and therefore only the boot
>> vcpu's info lives in the shared info page).
>>
>> Existing tests adjusted accordingly, and new tests added for the
>> 'maxvcpus' setting.
>>
>> Signed-off-by: Jim Fehlig <jfehlig@xxxxxxxx>
>> ---
>>
>> This is a respin of Ian's patch [1] to support parsing/formatting of the
>> 'maxvcpus' xm and xl config setting. It goes a bit further and removes
>> the old Xen 3.x 'vcpu_avail' setting and lifts the maxvcpus limit of
>> MAX_VIRT_CPUS entirely.
>>
>> The patch is based on my recent series [2] removing xend config version from
>> the codebase.
>>
>> [1] https://www.redhat.com/archives/libvir-list/2015-November/msg01155.html
>> [2] https://www.redhat.com/archives/libvir-list/2015-December/msg00616.html
>>
>>
>>  src/xenconfig/xen_common.c                    | 25 +++++++++++----------
>>  tests/xlconfigdata/test-paravirt-maxvcpus.cfg | 13 +++++++++++
>>  tests/xlconfigdata/test-paravirt-maxvcpus.xml | 28 ++++++++++++++++++++++++
>>  tests/xlconfigtest.c                          |  1 +
>>  tests/xmconfigdata/test-paravirt-maxvcpus.cfg | 13 +++++++++++
>>  tests/xmconfigdata/test-paravirt-maxvcpus.xml | 31 
>> +++++++++++++++++++++++++++
>>  tests/xmconfigdata/test-paravirt-vcpu.cfg     |  4 ++--
>>  tests/xmconfigtest.c                          |  1 +
>>  8 files changed, 101 insertions(+), 15 deletions(-)
> ACK

Thanks, pushed now.

Regards,
Jim


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