Commit f800650a authored by Maxim Levitsky's avatar Maxim Levitsky Committed by Paolo Bonzini
Browse files

KVM: x86: SVM: add module param to control TSC scaling 



This allows to easily simulate a CPU without this feature.

Signed-off-by: default avatarMaxim Levitsky <mlevitsk@redhat.com>
Message-Id: <20210914154825.104886-13-mlevitsk@redhat.com>
Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
parent 36e8194d

arch/x86/kvm/svm/svm.c

+18 −6
Original line number Diff line number Diff line
@@ -190,6 +190,9 @@ module_param(vgif, int, 0444); 
static int lbrv = true;

module_param(lbrv, int, 0444);



static int tsc_scaling = true;

module_param(tsc_scaling, int, 0444);



/*

 * enable / disable AVIC.  Because the defaults differ for APICv

 * support between VMX and SVM we cannot use module_param_named.
@@ -470,7 +473,7 @@ static int has_svm(void) 
static void svm_hardware_disable(void)

{

	/* Make sure we clean up behind us */

	if (static_cpu_has(X86_FEATURE_TSCRATEMSR))

	if (tsc_scaling)

		wrmsrl(MSR_AMD64_TSC_RATIO, TSC_RATIO_DEFAULT);



	cpu_svm_disable();
@@ -513,6 +516,10 @@ static int svm_hardware_enable(void) 
	wrmsrl(MSR_VM_HSAVE_PA, __sme_page_pa(sd->save_area));



	if (static_cpu_has(X86_FEATURE_TSCRATEMSR)) {

		/*

		 * Set the default value, even if we don't use TSC scaling

		 * to avoid having stale value in the msr

		 */

		wrmsrl(MSR_AMD64_TSC_RATIO, TSC_RATIO_DEFAULT);

		__this_cpu_write(current_tsc_ratio, TSC_RATIO_DEFAULT);

	}
@@ -980,11 +987,16 @@ static __init int svm_hardware_setup(void) 
	if (boot_cpu_has(X86_FEATURE_FXSR_OPT))

		kvm_enable_efer_bits(EFER_FFXSR);



	if (boot_cpu_has(X86_FEATURE_TSCRATEMSR)) {

	if (tsc_scaling) {

		if (!boot_cpu_has(X86_FEATURE_TSCRATEMSR)) {

			tsc_scaling = false;

		} else {

			pr_info("TSC scaling supported\n");

			kvm_has_tsc_control = true;

			kvm_max_tsc_scaling_ratio = TSC_RATIO_MAX;

			kvm_tsc_scaling_ratio_frac_bits = 32;

		}

	}



	tsc_aux_uret_slot = kvm_add_user_return_msr(MSR_TSC_AUX);
@@ -1496,7 +1508,7 @@ static void svm_prepare_guest_switch(struct kvm_vcpu *vcpu) 
		vmsave(__sme_page_pa(sd->save_area));

	}



	if (static_cpu_has(X86_FEATURE_TSCRATEMSR)) {

	if (tsc_scaling) {

		u64 tsc_ratio = vcpu->arch.tsc_scaling_ratio;

		if (tsc_ratio != __this_cpu_read(current_tsc_ratio)) {

			__this_cpu_write(current_tsc_ratio, tsc_ratio);