Add a guest assert in the PMU counters test to verify that KVM stuffs
the vCPU's post-RESET value to globally enable all general purpose
counters. Per Intel's SDM,
IA32_PERF_GLOBAL_CTRL: Sets bits n-1:0 and clears the upper bits.
and
Where "n" is the number of general-purpose counters available in
the processor.
For the edge case where there are zero GP counters, follow the spirit
of the architecture, not the SDM's literal wording, which doesn't account
for this possibility and would require the CPU to set _all_ bits in
PERF_GLOBAL_CTRL.
Reviewed-by: Dapeng Mi <dapeng1.mi@linux.intel.com>
Tested-by: Dapeng Mi <dapeng1.mi@linux.intel.com>
Link: https://lore.kernel.org/r/20240309013641.1413400-3-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
Although the fixed counter 3 and its exclusive pseudo slots event are
not supported by KVM yet, the architectural slots event is supported by
KVM and can be programmed on any GP counter. Thus add validation for this
architectural slots event.
Top-down slots event "counts the total number of available slots for an
unhalted logical processor, and increments by machine-width of the
narrowest pipeline as employed by the Top-down Microarchitecture
Analysis method."
As for the slot, it's an abstract concept which indicates how many
uops (decoded from instructions) can be processed simultaneously
(per cycle) on HW. In Top-down Microarchitecture Analysis (TMA) method,
the processor is divided into two parts, frond-end and back-end. Assume
there is a processor with classic 5-stage pipeline, fetch, decode,
execute, memory access and register writeback. The former 2 stages
(fetch/decode) are classified to frond-end and the latter 3 stages are
classified to back-end.
In modern Intel processors, a complicated instruction would be decoded
into several uops (micro-operations) and so these uops can be processed
simultaneously and then improve the performance. Thus, assume a
processor can decode and dispatch 4 uops in front-end and execute 4 uops
in back-end simultaneously (per-cycle), so the machine-width of this
processor is 4 and this processor has 4 topdown slots per-cycle.
If a slot is spare and can be used to process a new upcoming uop, then
the slot is available, but if a uop occupies a slot for several cycles
and can't be retired (maybe blocked by memory access), then this slot is
stall and unavailable.
Considering the testing instruction sequence can't be macro-fused on x86
platforms, the measured slots count should not be less than
NUM_INSNS_RETIRED. Thus assert the slots count against NUM_INSNS_RETIRED.
pmu_counters_test passed with this patch on Intel Sapphire Rapids.
About the more information about TMA method, please refer the below link.
https://www.intel.com/content/www/us/en/docs/vtune-profiler/cookbook/2023-0/top-down-microarchitecture-analysis-method.html
Signed-off-by: Dapeng Mi <dapeng1.mi@linux.intel.com>
Link: https://lore.kernel.org/r/20240218043003.2424683-1-dapeng1.mi@linux.intel.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
Extend the read/write PMU counters subtest to verify that RDPMC also reads
back the written value. Opportunsitically verify that attempting to use
the "fast" mode of RDPMC fails, as the "fast" flag is only supported by
non-architectural PMUs, which KVM doesn't virtualize.
Tested-by: Dapeng Mi <dapeng1.mi@linux.intel.com>
Link: https://lore.kernel.org/r/20240109230250.424295-30-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
Expand the PMU counters test to verify that LLC references and misses have
non-zero counts when the code being executed while the LLC event(s) is
active is evicted via CFLUSH{,OPT}. Note, CLFLUSH{,OPT} requires a fence
of some kind to ensure the cache lines are flushed before execution
continues. Use MFENCE for simplicity (performance is not a concern).
Suggested-by: Jim Mattson <jmattson@google.com>
Reviewed-by: Dapeng Mi <dapeng1.mi@linux.intel.com>
Tested-by: Dapeng Mi <dapeng1.mi@linux.intel.com>
Link: https://lore.kernel.org/r/20240109230250.424295-22-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
Add test cases to verify that Intel's Architectural PMU events work as
expected when they are available according to guest CPUID. Iterate over a
range of sane PMU versions, with and without full-width writes enabled,
and over interesting combinations of lengths/masks for the bit vector that
enumerates unavailable events.
Test up to vPMU version 5, i.e. the current architectural max. KVM only
officially supports up to version 2, but the behavior of the counters is
backwards compatible, i.e. KVM shouldn't do something completely different
for a higher, architecturally-defined vPMU version. Verify KVM behavior
against the effective vPMU version, e.g. advertising vPMU 5 when KVM only
supports vPMU 2 shouldn't magically unlock vPMU 5 features.
According to Intel SDM, the number of architectural events is reported
through CPUID.0AH:EAX[31:24] and the architectural event x is supported
if EBX[x]=0 && EAX[31:24]>x.
Handcode the entirety of the measured section so that the test can
precisely assert on the number of instructions and branches retired.
Co-developed-by: Like Xu <likexu@tencent.com>
Signed-off-by: Like Xu <likexu@tencent.com>
Signed-off-by: Jinrong Liang <cloudliang@tencent.com>
Co-developed-by: Sean Christopherson <seanjc@google.com>
Tested-by: Dapeng Mi <dapeng1.mi@linux.intel.com>
Link: https://lore.kernel.org/r/20240109230250.424295-17-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
