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From: Dan Carpenter <dan.carpenter@oracle.com>
To: wehuang@redhat.com
Cc: kvm@vger.kernel.org
Subject: [bug report] KVM: x86/vPMU: Define kvm_pmu_ops to support vPMU function dispatch
Date: Thu, 18 May 2017 10:40:41 +0300	[thread overview]
Message-ID: <20170518074041.56rezj4wnpzrrhk7@mwanda> (raw)

Hello Wei Huang,

The patch 25462f7f5295: "KVM: x86/vPMU: Define kvm_pmu_ops to support
vPMU function dispatch" from Jun 19, 2015, leads to the following
static checker warning:

	arch/x86/kvm/pmu_intel.c:297 intel_pmu_refresh()
	warn: potential left shift more than type allows '0-32'

arch/x86/kvm/pmu_intel.c
   277          pmu->version = eax.split.version_id;
   278          if (!pmu->version)
   279                  return;
   280  
   281          pmu->nr_arch_gp_counters = min_t(int, eax.split.num_counters,
   282                                          INTEL_PMC_MAX_GENERIC);
                                                ^^^^^^^^^^^^^^^^^^^^^
We cap ->nr_arch_gp_counters at 32.

   283          pmu->counter_bitmask[KVM_PMC_GP] = ((u64)1 << eax.split.bit_width) - 1;
   284          pmu->available_event_types = ~entry->ebx &
   285                                          ((1ull << eax.split.mask_length) - 1);
   286  
   287          if (pmu->version == 1) {
   288                  pmu->nr_arch_fixed_counters = 0;
   289          } else {
   290                  pmu->nr_arch_fixed_counters =
   291                          min_t(int, edx.split.num_counters_fixed,
   292                                  INTEL_PMC_MAX_FIXED);
   293                  pmu->counter_bitmask[KVM_PMC_FIXED] =
   294                          ((u64)1 << edx.split.bit_width_fixed) - 1;
   295          }
   296  
   297          pmu->global_ctrl = ((1 << pmu->nr_arch_gp_counters) - 1) |
                                     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
Potential shift wrapping bug.

   298                  (((1ull << pmu->nr_arch_fixed_counters) - 1) << INTEL_PMC_IDX_FIXED);
   299          pmu->global_ctrl_mask = ~pmu->global_ctrl;
   300  
   301          entry = kvm_find_cpuid_entry(vcpu, 7, 0);
   302          if (entry &&
   303              (boot_cpu_has(X86_FEATURE_HLE) || boot_cpu_has(X86_FEATURE_RTM)) &&
   304              (entry->ebx & (X86_FEATURE_HLE|X86_FEATURE_RTM)))
   305                  pmu->reserved_bits ^= HSW_IN_TX|HSW_IN_TX_CHECKPOINTED;

regards,
dan carpenter

                 reply	other threads:[~2017-05-18  7:40 UTC|newest]

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