KVM: x86/pmu: Disallow "fast" RDPMC for architectural Intel PMUs

Inject #GP on RDPMC if the "fast" flag is set for architectural Intel
PMUs, i.e. if the PMU version is non-zero.  Per Intel's SDM, and confirmed
on bare metal, the "fast" flag is supported only for non-architectural
PMUs, and is reserved for architectural PMUs.

  If the processor does not support architectural performance monitoring
  (CPUID.0AH:EAX[7:0]=0), ECX[30:0] specifies the index of the PMC to be
  read. Setting ECX[31] selects “fast” read mode if supported. In this mode,
  RDPMC returns bits 31:0 of the PMC in EAX while clearing EDX to zero.

  If the processor does support architectural performance monitoring
  (CPUID.0AH:EAX[7:0] ≠ 0), ECX[31:16] specifies type of PMC while ECX[15:0]
  specifies the index of the PMC to be read within that type. The following
  PMC types are currently defined:
  — General-purpose counters use type 0. The index x (to read IA32_PMCx)
    must be less than the value enumerated by CPUID.0AH.EAX[15:8] (thus
    ECX[15:8] must be zero).
  — Fixed-function counters use type 4000H. The index x (to read
    IA32_FIXED_CTRx) can be used if either CPUID.0AH.EDX[4:0] > x or
    CPUID.0AH.ECX[x] = 1 (thus ECX[15:5] must be 0).
  — Performance metrics use type 2000H. This type can be used only if
    IA32_PERF_CAPABILITIES.PERF_METRICS_AVAILABLE[bit 15]=1. For this type,
    the index in ECX[15:0] is implementation specific.

Opportunistically WARN if KVM ever actually tries to complete RDPMC for a
non-architectural PMU, and drop the non-existent "support" for fast RDPMC,
as KVM doesn't support such PMUs, i.e. kvm_pmu_rdpmc() should reject the
RDPMC before getting to the Intel code.

Fixes: f5132b01386b ("KVM: Expose a version 2 architectural PMU to a guests")
Fixes: 67f4d4288c35 ("KVM: x86: rdpmc emulation checks the counter incorrectly")
Reviewed-by: Dapeng Mi <dapeng1.mi@linux.intel.com>
Tested-by: Dapeng Mi <dapeng1.mi@linux.intel.com>
Link: https://lore.kernel.org/r/20240109230250.424295-10-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>

0 files changed, 0 insertions, 0 deletions