kvm: Handle reads of SandyBridge RAPL PMU MSRs rather than injecting #GP

Linux 3.14 unconditionally reads the RAPL PMU MSRs on boot, without handling
General Protection Faults on reading those MSRs. Rather than injecting a #GP,
which prevents boot, handle the MSRs by returning 0 for their data. Zero was
checked to be safe by code review of the RAPL PMU driver and in discussion
with the original driver author (eranian@google.com).

Signed-off-by: Venkatesh Srinivas <venkateshs@google.com>
Signed-off-by: Jon Cargille <jcargill@google.com>
Reviewed-by: Jim Mattson <jmattson@google.com>
Message-Id: <20200416184254.248374-1-jcargill@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 3cc3f67..919d3c8 100644 (file)
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -3060,6 +3060,17 @@ int kvm_get_msr_common(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
        case MSR_IA32_PERF_CTL:
        case MSR_AMD64_DC_CFG:
        case MSR_F15H_EX_CFG:
+       /*
+        * Intel Sandy Bridge CPUs must support the RAPL (running average power
+        * limit) MSRs. Just return 0, as we do not want to expose the host
+        * data here. Do not conditionalize this on CPUID, as KVM does not do
+        * so for existing CPU-specific MSRs.
+        */
+       case MSR_RAPL_POWER_UNIT:
+       case MSR_PP0_ENERGY_STATUS:     /* Power plane 0 (core) */
+       case MSR_PP1_ENERGY_STATUS:     /* Power plane 1 (graphics uncore) */
+       case MSR_PKG_ENERGY_STATUS:     /* Total package */
+       case MSR_DRAM_ENERGY_STATUS:    /* DRAM controller */
                msr_info->data = 0;
                break;
        case MSR_F15H_PERF_CTL0 ... MSR_F15H_PERF_CTR5: