Re: [RFC v2 3/5] i386/kvm: Support event with select & umask format in KVM PMU filter

[Markus Armbruster <armbru@redhat.com>]

Zhao Liu <zhao1.liu@intel.com> writes:

> The select&umask is the common way for x86 to identify the PMU event,
> so support this way as the "x86-default" format in kvm-pmu-filter
> object.

So, format 'raw' lets you specify the PMU event code as a number, wheras
'x86-default' lets you specify it as select and umask, correct?

Why do we want both?

> Signed-off-by: Zhao Liu <zhao1.liu@intel.com>

[...]

> diff --git a/qapi/kvm.json b/qapi/kvm.json
> index d51aeeba7cd8..93b869e3f90c 100644
> --- a/qapi/kvm.json
> +++ b/qapi/kvm.json
> @@ -27,11 +27,13 @@
>  #
>  # @raw: the encoded event code that KVM can directly consume.
>  #
> +# @x86-default: standard x86 encoding format with select and umask.

Why is this named -default?

> +#
>  # Since 10.0
>  ##
>  { 'enum': 'KVMPMUEventEncodeFmt',
>    'prefix': 'KVM_PMU_EVENT_FMT',
> -  'data': ['raw'] }
> +  'data': ['raw', 'x86-default'] }
>  
>  ##
>  # @KVMPMURawEvent:
> @@ -46,6 +48,25 @@
>  { 'struct': 'KVMPMURawEvent',
>    'data': { 'code': 'uint64' } }
>  
> +##
> +# @KVMPMUX86DefalutEvent:

Default, I suppose.

> +#
> +# x86 PMU event encoding with select and umask.
> +# raw_event = ((select & 0xf00UL) << 24) | \
> +#              (select) & 0xff) | \
> +#              ((umask) & 0xff) << 8)

Sphinx rejects this with "Unexpected indentation."

Is the formula needed here?

> +#
> +# @select: x86 PMU event select field, which is a 12-bit unsigned
> +#     number.
> +#
> +# @umask: x86 PMU event umask field.
> +#
> +# Since 10.0
> +##
> +{ 'struct': 'KVMPMUX86DefalutEvent',
> +  'data': { 'select': 'uint16',
> +            'umask': 'uint8' } }
> +
>  ##
>  # @KVMPMUFilterEvent:
>  #
> @@ -58,7 +79,8 @@
>  { 'union': 'KVMPMUFilterEvent',
>    'base': { 'format': 'KVMPMUEventEncodeFmt' },
>    'discriminator': 'format',
> -  'data': { 'raw': 'KVMPMURawEvent' } }
> +  'data': { 'raw': 'KVMPMURawEvent',
> +            'x86-default': 'KVMPMUX86DefalutEvent' } }
>  
>  ##
>  # @KVMPMUFilterProperty:
> @@ -86,6 +108,23 @@
>  { 'struct': 'KVMPMURawEventVariant',
>    'data': { 'code': 'str' } }
>  
> +##
> +# @KVMPMUX86DefalutEventVariant:
> +#
> +# The variant of KVMPMUX86DefalutEvent with the string, rather than
> +# the numeric value.
> +#
> +# @select: x86 PMU event select field.  This field is a 12-bit
> +#     unsigned number string.
> +#
> +# @umask: x86 PMU event umask field. This field is a uint8 string.

Why are these strings?  How are they parsed into numbers?

> +#
> +# Since 10.0
> +##
> +{ 'struct': 'KVMPMUX86DefalutEventVariant',
> +  'data': { 'select': 'str',
> +            'umask': 'str' } }
> +
>  ##
>  # @KVMPMUFilterEventVariant:
>  #
> @@ -98,7 +137,8 @@
>  { 'union': 'KVMPMUFilterEventVariant',
>    'base': { 'format': 'KVMPMUEventEncodeFmt' },
>    'discriminator': 'format',
> -  'data': { 'raw': 'KVMPMURawEventVariant' } }
> +  'data': { 'raw': 'KVMPMURawEventVariant',
> +            'x86-default': 'KVMPMUX86DefalutEventVariant' } }
>  
>  ##
>  # @KVMPMUFilterPropertyVariant:

[...]