KVM: x86: SVM: fix tsc scaling when the host doesn't support it

It was decided that when TSC scaling is not supported, the virtual MSR_AMD64_TSC_RATIO should still have the default '1.0' value. However in this case kvm_max_tsc_scaling_ratio is not set, which breaks various assumptions. Fix this by always calculating kvm_max_tsc_scaling_ratio regardless of host support. For consistency, do the same for VMX. Suggested-by: Paolo Bonzini <[email protected]> Signed-off-by: Maxim Levitsky <[email protected]> Message-Id: <[email protected]> Signed-off-by: Paolo Bonzini <[email protected]>
josf · Apr 2, 2022 · 8809931 · 8809931
1 parent f37b735
commit 8809931
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Showing 3 changed files with 6 additions and 9 deletions.
diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c
@@ -4752,10 +4752,10 @@ static __init int svm_hardware_setup(void)
 		} else {
 			pr_info("TSC scaling supported\n");
 			kvm_has_tsc_control = true;
-			kvm_max_tsc_scaling_ratio = SVM_TSC_RATIO_MAX;
-			kvm_tsc_scaling_ratio_frac_bits = 32;
 		}
 	}
+	kvm_max_tsc_scaling_ratio = SVM_TSC_RATIO_MAX;
+	kvm_tsc_scaling_ratio_frac_bits = 32;
 
 	tsc_aux_uret_slot = kvm_add_user_return_msr(MSR_TSC_AUX);
 

diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
@@ -7980,12 +7980,11 @@ static __init int hardware_setup(void)
 	if (!enable_apicv)
 		vmx_x86_ops.sync_pir_to_irr = NULL;
 
-	if (cpu_has_vmx_tsc_scaling()) {
+	if (cpu_has_vmx_tsc_scaling())
 		kvm_has_tsc_control = true;
-		kvm_max_tsc_scaling_ratio = KVM_VMX_TSC_MULTIPLIER_MAX;
-		kvm_tsc_scaling_ratio_frac_bits = 48;
-	}
 
+	kvm_max_tsc_scaling_ratio = KVM_VMX_TSC_MULTIPLIER_MAX;
+	kvm_tsc_scaling_ratio_frac_bits = 48;
 	kvm_has_bus_lock_exit = cpu_has_vmx_bus_lock_detection();
 
 	set_bit(0, vmx_vpid_bitmap); /* 0 is reserved for host */

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
@@ -11602,10 +11602,8 @@ int kvm_arch_hardware_setup(void *opaque)
 		u64 max = min(0x7fffffffULL,
 			      __scale_tsc(kvm_max_tsc_scaling_ratio, tsc_khz));
 		kvm_max_guest_tsc_khz = max;
-
-		kvm_default_tsc_scaling_ratio = 1ULL << kvm_tsc_scaling_ratio_frac_bits;
 	}
-
+	kvm_default_tsc_scaling_ratio = 1ULL << kvm_tsc_scaling_ratio_frac_bits;
 	kvm_init_msr_list();
 	return 0;
 }