On Mon, Jun 6, 2022 at 10:53 AM Aaron Lewis <aaronlewis@xxxxxxxxxx> wrote: > > When building an event list for the pmu event filter, fitting all the > events in the limited space can be a challenge. It becomes > particularly challenging when trying to include various unit mask > combinations for a particular event the guest is allow to or not allow > to program. Instead of increasing the size of the list to allow for > these, add a new encoding in the pmu event filter's events field. These > encoded events can then be used to test against the event the guest is > attempting to program to determine if the guest should have access to > it. > > The encoded values are: mask, match, and invert. When filtering events > the mask is applied to the guest's unit mask to see if it matches the > match value (ie: unit_mask & mask == match). If it does and the pmu > event filter is an allow list the event is allowed, and denied if it's > a deny list. Additionally, the result is reversed if the invert flag > is set in the encoded event. > > This feature is enabled by setting the flags field to > KVM_PMU_EVENT_FLAG_MASKED_EVENTS. > > Events can be encoded by using KVM_PMU_EVENT_ENCODE_MASKED_EVENT(). > > It is an error to have a bit set outside valid encoded bits, and calls > to KVM_SET_PMU_EVENT_FILTER will return -EINVAL in such cases, > including bits that are set in the high nybble[1] for AMD if called on > Intel. > > [1] bits 35:32 in the event and bits 11:8 in the eventsel. > > Signed-off-by: Aaron Lewis <aaronlewis@xxxxxxxxxx> > --- > Documentation/virt/kvm/api.rst | 46 +++++++-- > arch/x86/include/asm/kvm-x86-pmu-ops.h | 1 + > arch/x86/include/uapi/asm/kvm.h | 8 ++ > arch/x86/kvm/pmu.c | 128 ++++++++++++++++++++++--- > arch/x86/kvm/pmu.h | 1 + > arch/x86/kvm/svm/pmu.c | 12 +++ > arch/x86/kvm/vmx/pmu_intel.c | 12 +++ > 7 files changed, 190 insertions(+), 18 deletions(-) > > diff --git a/Documentation/virt/kvm/api.rst b/Documentation/virt/kvm/api.rst > index 11e00a46c610..4e904772da5b 100644 > --- a/Documentation/virt/kvm/api.rst > +++ b/Documentation/virt/kvm/api.rst > @@ -5017,7 +5017,13 @@ 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 events field. > + 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. > > :: > > @@ -5030,14 +5036,42 @@ using this ioctl. > __u64 events[0]; > }; > > -This ioctl restricts the set of PMU events that the guest can program. > -The argument holds a list of events which will be allowed or denied. > -The eventsel+umask of each event the guest attempts to program is compared > -against the events field to determine whether the guest should have access. > +This ioctl restricts the set of PMU events the guest can program. The > +argument holds a list of events which will be allowed or denied. > + > The events field only controls general purpose counters; fixed purpose > counters are controlled by the fixed_counter_bitmap. > > -No flags are defined yet, the field must be zero. > +Valid values for 'flags':: > + > +``0`` > + > +This is the default behavior for the pmu event filter, and used when the > +flags field is clear. In this mode the eventsel+umask for the event the > +guest is attempting to program is compared against each event in the events > +field to determine whether the guest should have access to it. > + > +``KVM_PMU_EVENT_FLAG_MASKED_EVENTS`` > + > +In this mode each event in the events field will be encoded with mask, match, > +and invert values in addition to an eventsel. These encoded events will be > +matched against the event the guest is attempting to program to determine > +whether the guest should have access to it. When matching an encoded event > +with a guest event these steps are followed: > + 1. Match the encoded eventsel to the guest eventsel. > + 2. If that matches, match the mask and match values from the encoded event to > + the guest's unit mask (ie: unit_mask & mask == match). > + 3. If that matches, the guest is allow to program the event if its an allow > + list or the guest is not allow to program the event if its a deny list. > + 4. If the invert value is set in the encoded event, reverse the meaning of #3 > + (ie: deny if its an allow list, allow if it's a deny list). The invert flag introduces some ambiguity. What if a particular event matches two of the masked filter entries: one with an invert flag and one without? > +To encode an event in the pmu_event_filter use > +KVM_PMU_EVENT_ENCODE_MASKED_EVENT(). > + > +If a bit is set in an encoded event that is not apart of the bits used for Nit: "a part"?
