On Wed, Aug 31, 2022 at 9:21 AM Aaron Lewis <aaronlewis@xxxxxxxxxx> wrote:
>
> When building a list of filter events, it can sometimes be a challenge
> to fit all the events needed to adequately restrict the guest into the
> limited space available in the pmu event filter. This stems from the
> fact that the pmu event filter requires each raw event (i.e. event
> select + unit mask) be listed, when the intention might be to restrict
> the event select all together, regardless of it's unit mask. Instead
> of increasing the number of filter events in the pmu event filter, add
> a new encoding that is able to do a more generalized match on the unit
> mask.
>
> Introduce masked events as a new encoding that the pmu event filter
> understands in addition to raw events. A masked event has the fields:
> mask, match, and exclude. When filtering based on these events, the
> mask is applied to the guest's unit mask to see if it matches the match
> value (i.e. unit_mask & mask == match). The exclude bit can then be
> used to exclude events from that match. E.g. for a given event select,
> if it's easier to say which unit mask values shouldn't be filtered, a
> masked event can be set up to match all possible unit mask values, then
> another masked event can be set up to match the unit mask values that
> shouldn't be filtered.
>
> Userspace can query to see if this feature exists by looking for the
> capability, KVM_CAP_PMU_EVENT_MASKED_EVENTS.
>
> This feature is enabled by setting the flags field in the pmu event
> filter to KVM_PMU_EVENT_FLAG_MASKED_EVENTS.
>
> Events can be encoded by using KVM_PMU_EVENT_ENCODE_MASKED_ENTRY().
>
> It is an error to have a bit set outside the valid bits for a masked
> event, and calls to KVM_SET_PMU_EVENT_FILTER will return -EINVAL in
> such cases, including the high bits (11:8) of the event select if
> called on Intel.
>
> Signed-off-by: Aaron Lewis <aaronlewis@xxxxxxxxxx>
> ---
> Documentation/virt/kvm/api.rst | 81 ++++++++++++++++--
> arch/x86/include/uapi/asm/kvm.h | 28 ++++++
> arch/x86/kvm/pmu.c | 145 +++++++++++++++++++++++++++-----
> arch/x86/kvm/pmu.h | 32 +++++--
> arch/x86/kvm/x86.c | 1 +
> include/uapi/linux/kvm.h | 1 +
> 6 files changed, 255 insertions(+), 33 deletions(-)
>
> diff --git a/Documentation/virt/kvm/api.rst b/Documentation/virt/kvm/api.rst
> index abd7c32126ce..e7783e41c590 100644
> --- a/Documentation/virt/kvm/api.rst
> +++ b/Documentation/virt/kvm/api.rst
> @@ -5027,7 +5027,13 @@ using this ioctl.
> :Architectures: x86
> :Type: vm ioctl
> :Parameters: struct kvm_pmu_event_filter (in)
> -:Returns: 0 on success, -1 on error
> +:Returns: 0 on success,
> + -EFAULT args[0] cannot be accessed.
> + -EINVAL args[0] contains invalid data in the filter or filter events.
> + Note: event validation is only done for modes where
> + the flags field is non-zero.
> + -E2BIG nevents is too large.
> + -ENOMEM not enough memory to allocate the filter.
I assume that the ioctl returns -1 on error, but that errno is set to
one of the errors listed above (in its positive form).
So...
:Returns: 0 on success, -1 on error
Errors:
====== ============================================
EFAULT args[0] cannot be accessed
EINVAL args[0] contains invalid data in the filter or filter events
E2BIG nevents is too large
EBUSY not enough memory to allocate the filter
====== ============================================
> @@ -647,7 +719,34 @@ static void convert_to_filter_events(struct kvm_pmu_event_filter *filter)
> for (i = 0; i < filter->nevents; i++) {
> u64 e = filter->events[i];
>
> - filter->events[i] = encode_filter_entry(e);
> + filter->events[i] = encode_filter_entry(e, filter->flags);
> + }
> +}
> +
> +/*
> + * Sort will order the list by exclude, then event select. This function will
> + * then index the sublists of event selects such that when a search is done on
> + * the list, the head of the event select sublist is returned. This simpilfies
Nit: simplifies
With the documentation changes,
Reviewed-by: Jim Mattson <jmattson@xxxxxxxxxx>
