Re: [PATCH v9] arm/kvm: Enable support for KVM_ARM_VCPU_PMU_V3_FILTER

Shaoqin Huang <shahuang@xxxxxxxxxx> · Mon, 27 May 2024 14:41:01 +0800

Hi Zhao,

Thanks for your proposed idea. If you are willing to take the PMU Filter 
Enabling work, you can do it. I won't update this series anymore due to 
the QAPI restriction. I really appreciate if you can implement that.

Thanks,
Shaoqin

On 5/13/24 14:52, Zhao Liu wrote:
Hi Daniel,

Please describe it in terms of a QAPI definition, as that's what we're
striving for with all QEMU public interfaces. Once the QAPI design is
agreed, then the -object mapping is trivial, as -object's JSON format
supports arbitrary QAPI structures.

Thank you for your guidance!

I rethought and and modified my previous proposal:

Let me show the command examples firstly:
   * Add a single event:
     (x86) -object kvm-pmu-event,id=e0,action=allow,format=x86-default,\
                   select=0x3c,umask=0x00
     (arm or general) -object kvm-pmu-event,id=e1,action=deny,\
                              format=raw,code=0x01

   * Add a counter bitmap:
     (x86) -object kvm-pmu-counter,id=cnt,action=allow,type=x86-fixed,\
                   bitmap=0xffff0000

   * Add an event list (must use Json syntax format):
    (x86) -object '{"qom-type":"kvm-pmu-event-list","id"="filter0","action"="allow","format"="x86-default","events=[{"select"=0x3c,"umask"=0x00},{"select"=0x2e,"umask"=0x4f}]'
    (arm) -object '{"qom-type":"kvm-pmu-event-list","id"="filter1","action"="allow","format"="raw","events"=[{"code"=0x01},{"code"=0x02}]'

The specific JSON definitions are as follows (IIUC, this is "in terms of
a QAPI definition", right? ;-)):
* Define PMU event and counter bitmap with JSON format:
   - basic filter action:

   { 'enum': 'KVMPMUFilterAction',
     'prefix': 'KVM_PMU_FILTER_ACTION',
     'data': ['deny', 'allow' ] }

   - PMU counter:

   { 'enum': 'KVMPMUCounterType',
     'prefix': 'KVM_PMU_COUNTER_TYPE',
     'data': [ 'x86-fixed' ] }

   { 'struct': 'KVMPMUX86FixedCounter',
     'data': { 'bitmap': 'uint32' } }

   - PMU events (total 3 formats):

   # 3 encoding formats: "raw" is compatible with shaoqin's ARM format as
   # well as the x86 raw format, and could support other architectures in
   # the future.
   { 'enum': 'KVMPMUEventEncodeFmt',
     'prefix': 'KVM_PMU_EVENT_ENCODE_FMT',
     'data': ['raw', 'x86-default', 'x86-masked-entry' ] }

   # A general format.
   { 'struct': 'KVMPMURawEvent',
     'data': { 'code': 'uint64' } }

   # x86-specific
   { 'struct': 'KVMPMUX86DefalutEvent',
     'data': { 'select': 'uint16',
               'umask': 'uint16' } }

   # another x86 specific
   { 'struct': 'KVMPMUX86MaskedEntry',
     'data': { 'select': 'uint16',
               'match': 'uint8',
               'mask': 'uint8',
               'exclude': 'bool' } }

   # And their list wrappers:
   { 'struct': 'KVMPMURawEventList',
     'data': { 'events': ['KVMPMURawEvent'] } }

   { 'struct': 'KVMPMUX86DefalutEventList',
     'data': { 'events': ['KVMPMUX86DefalutEvent'] } }

   { 'struct': 'KVMPMUX86MaskedEntryList',
     'data': { 'events': ['KVMPMUX86MaskedEntryList'] } }

Based on the above basic structs, we could provide 3 new more qom-types:
   - 'kvm-pmu-counter': 'KVMPMUFilterCounter'

   # This is a single object option to configure PMU counter
   # bitmap filter.
   { 'union': 'KVMPMUFilterCounter',
     'base': { 'action': 'KVMPMUFilterAction',
               'type': 'KVMPMUCounterType' },
     'discriminator': 'type',
     'data': { 'x86-fixed': 'KVMPMUX86FixedCounter' } }

   - 'kvm-pmu-counter': 'KVMPMUFilterCounter'

   # This option is used to configure a single PMU event for
   # PMU filter.
   { 'union': 'KVMPMUFilterEvent',
     'base': { 'action': 'KVMPMUFilterAction',
               'format': 'KVMPMUEventEncodeFmt' },
     'discriminator': 'format',
     'data': { 'raw': 'KVMPMURawEvent',
               'x86-default': 'KVMPMUX86DefalutEvent',
               'x86-masked-entry': 'KVMPMUX86MaskedEntry' } }

   - 'kvm-pmu-event-list': 'KVMPMUFilterEventList'

   # Used to configure multiple events.
   { 'union': 'KVMPMUFilterEventList',
     'base': { 'action': 'KVMPMUFilterAction',
               'format': 'KVMPMUEventEncodeFmt' },
     'discriminator': 'format',
     'data': { 'raw': 'KVMPMURawEventList',
               'x86-default': 'KVMPMUX86DefalutEventList',
               'x86-masked-entry': 'KVMPMUX86MaskedEntryList' } }

Compared to Shaoqin's original format, kvm-pmu-event-list is not able to
enumerate events continuously (similar to 0x00-0x30 before), and now
user must enumerate events one by one individually.

What do you think about the above 3 new commands?

Thanks and Best Regards,
Zhao

--
Shaoqin