KVM: x86: Making the module parameter of vPMU more common

The new module parameter to control PMU virtualization should apply
to Intel as well as AMD, for situations where userspace is not trusted.
If the module parameter allows PMU virtualization, there could be a
new KVM_CAP or guest CPUID bits whereby userspace can enable/disable
PMU virtualization on a per-VM basis.

If the module parameter does not allow PMU virtualization, there
should be no userspace override, since we have no precedent for
authorizing that kind of override. If it's false, other counter-based
profiling features (such as LBR including the associated CPUID bits
if any) will not be exposed.

Change its name from "pmu" to "enable_pmu" as we have temporary
variables with the same name in our code like "struct kvm_pmu *pmu".

Fixes: 2213c1056c85 ("KVM: x86/svm: Add module param to control PMU virtualization")
Suggested-by : Jim Mattson <jmattson@google.com>
Signed-off-by: Like Xu <likexu@tencent.com>
Message-Id: <20220111073823.21885-1-likexu@tencent.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c
index 7eb046d907c65516d5f7317d02fe9337b5f0cd27..a7c280d2113b21e3d4df1f1b37cffe41691bf078 100644 (file)
--- a/arch/x86/kvm/cpuid.c
+++ b/arch/x86/kvm/cpuid.c
@@ -845,10 +845,10 @@ static inline int __do_cpuid_func(struct kvm_cpuid_array *array, u32 function)
                perf_get_x86_pmu_capability(&cap);
 
                /*
-                * Only support guest architectural pmu on a host
-                * with architectural pmu.
+                * The guest architecture pmu is only supported if the architecture
+                * pmu exists on the host and the module parameters allow it.
                 */
-               if (!cap.version)
+               if (!cap.version || !enable_pmu)
                        memset(&cap, 0, sizeof(cap));
 
                eax.split.version_id = min(cap.version, 2);

diff --git a/arch/x86/kvm/svm/pmu.c b/arch/x86/kvm/svm/pmu.c
index 12d8b301065ab940f0ee3c71d6f0e47d49038fbb..5aa45f13b16dca9e1b071c2bcd630641f6c719b9 100644 (file)
--- a/arch/x86/kvm/svm/pmu.c
+++ b/arch/x86/kvm/svm/pmu.c
@@ -101,7 +101,7 @@ static inline struct kvm_pmc *get_gp_pmc_amd(struct kvm_pmu *pmu, u32 msr,
 {
        struct kvm_vcpu *vcpu = pmu_to_vcpu(pmu);
 
-       if (!pmu)
+       if (!enable_pmu)
                return NULL;
 
        switch (msr) {

diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c
index c3d9006478a424c5bfad6a2cc29baa3d3b8cdf83..d8cac84fb2dcaeab2563464b27b040aa70937b65 100644 (file)
--- a/arch/x86/kvm/svm/svm.c
+++ b/arch/x86/kvm/svm/svm.c
@@ -192,10 +192,6 @@ module_param(vgif, int, 0444);
 static int lbrv = true;
 module_param(lbrv, int, 0444);
 
-/* enable/disable PMU virtualization */
-bool pmu = true;
-module_param(pmu, bool, 0444);
-
 static int tsc_scaling = true;
 module_param(tsc_scaling, int, 0444);
 
@@ -957,7 +953,7 @@ static __init void svm_set_cpu_caps(void)
                kvm_cpu_cap_set(X86_FEATURE_VIRT_SSBD);
 
        /* AMD PMU PERFCTR_CORE CPUID */
-       if (pmu && boot_cpu_has(X86_FEATURE_PERFCTR_CORE))
+       if (enable_pmu && boot_cpu_has(X86_FEATURE_PERFCTR_CORE))
                kvm_cpu_cap_set(X86_FEATURE_PERFCTR_CORE);
 
        /* CPUID 0x8000001F (SME/SEV features) */
@@ -1093,7 +1089,7 @@ static __init int svm_hardware_setup(void)
                        pr_info("LBR virtualization supported\n");
        }
 
-       if (!pmu)
+       if (!enable_pmu)
                pr_info("PMU virtualization is disabled\n");
 
        svm_set_cpu_caps();

diff --git a/arch/x86/kvm/svm/svm.h b/arch/x86/kvm/svm/svm.h
index 9f153c59f2c8d5ba1442ee8c9e855589e8a39a65..6d29421dd4bf3f4ed70c8775763866045bfd9053 100644 (file)
--- a/arch/x86/kvm/svm/svm.h
+++ b/arch/x86/kvm/svm/svm.h
@@ -32,7 +32,6 @@
 extern u32 msrpm_offsets[MSRPM_OFFSETS] __read_mostly;
 extern bool npt_enabled;
 extern bool intercept_smi;
-extern bool pmu;
 
 /*
  * Clean bits in VMCB.

diff --git a/arch/x86/kvm/vmx/capabilities.h b/arch/x86/kvm/vmx/capabilities.h
index c8029b7845b6fbd7197028022b2937988735559d..959b59d13b5accac49be87e9205de7521b2cbcb1 100644 (file)
--- a/arch/x86/kvm/vmx/capabilities.h
+++ b/arch/x86/kvm/vmx/capabilities.h
@@ -5,6 +5,7 @@
 #include <asm/vmx.h>
 
 #include "lapic.h"
+#include "x86.h"
 
 extern bool __read_mostly enable_vpid;
 extern bool __read_mostly flexpriority_enabled;
@@ -389,6 +390,9 @@ static inline u64 vmx_get_perf_capabilities(void)
 {
        u64 perf_cap = 0;
 
+       if (!enable_pmu)
+               return perf_cap;
+
        if (boot_cpu_has(X86_FEATURE_PDCM))
                rdmsrl(MSR_IA32_PERF_CAPABILITIES, perf_cap);
 

diff --git a/arch/x86/kvm/vmx/pmu_intel.c b/arch/x86/kvm/vmx/pmu_intel.c
index ffccfd9823c05c8f0c6e7048bc55f81a3c327131..466d18fc0c5da38cec6822b7f3af8d5439c72de9 100644 (file)
--- a/arch/x86/kvm/vmx/pmu_intel.c
+++ b/arch/x86/kvm/vmx/pmu_intel.c
@@ -487,7 +487,7 @@ static void intel_pmu_refresh(struct kvm_vcpu *vcpu)
        pmu->reserved_bits = 0xffffffff00200000ull;
 
        entry = kvm_find_cpuid_entry(vcpu, 0xa, 0);
-       if (!entry)
+       if (!entry || !enable_pmu)
                return;
        eax.full = entry->eax;
        edx.full = entry->edx;

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index a0bc637348b2f2cae2ef718584f638a3b4959f7e..52df8e6eaa57499075e2587bca487fb82869673c 100644 (file)
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -187,6 +187,11 @@ module_param(force_emulation_prefix, bool, S_IRUGO);
 int __read_mostly pi_inject_timer = -1;
 module_param(pi_inject_timer, bint, S_IRUGO | S_IWUSR);
 
+/* Enable/disable PMU virtualization */
+bool __read_mostly enable_pmu = true;
+EXPORT_SYMBOL_GPL(enable_pmu);
+module_param(enable_pmu, bool, 0444);
+
 /*
  * Restoring the host value for MSRs that are only consumed when running in
  * usermode, e.g. SYSCALL MSRs and TSC_AUX, can be deferred until the CPU

diff --git a/arch/x86/kvm/x86.h b/arch/x86/kvm/x86.h
index da7031e80f23a349b2b00dc2406e86a5aa1437f8..1ebd5a7594da74dbf536ae6737de8c874c73630c 100644 (file)
--- a/arch/x86/kvm/x86.h
+++ b/arch/x86/kvm/x86.h
@@ -336,6 +336,7 @@ extern u64 host_xcr0;
 extern u64 supported_xcr0;
 extern u64 host_xss;
 extern u64 supported_xss;
+extern bool enable_pmu;
 
 static inline bool kvm_mpx_supported(void)
 {