KVM: x86: Drop special XSAVE handling from guest_cpuid_has() (96be4e06) · Commits · 戴 / test

Now that KVM prevents setting host-reserved CR4 bits, drop the dedicated XSAVE check in guest_cpuid_has() in favor of open coding similar checks in the SVM/VMX XSAVES enabling flows. Note, checking boot_cpu_has(X86_FEATURE_XSAVE) in the XSAVES flows is technically redundant with respect to the CR4 reserved bit checks, e.g. XSAVES #UDs if CR4.OSXSAVE=0 and arch.xsaves_enabled is consumed if and only if CR4.OXSAVE=1 in guest. Keep (add?) the explicit boot_cpu_has() checks to help document KVM's usage of arch.xsaves_enabled. No functional change intended. Signed-off-by:

Sean Christopherson <sean.j.christopherson@intel.com> Signed-off-by:

Paolo Bonzini <pbonzini@redhat.com>

arch/x86/kvm/cpuid.h

+0 −4

Original line number	Diff line number	Diff line
		@@ -93,10 +93,6 @@ static __always_inline bool guest_cpuid_has(struct kvm_vcpu *vcpu, unsigned x86_
		{
		int *reg;

		if (x86_feature == X86_FEATURE_XSAVE &&
		!static_cpu_has(X86_FEATURE_XSAVE))
		return false;

		reg = guest_cpuid_get_register(vcpu, x86_feature);
		if (!reg)
		return false;

arch/x86/kvm/svm.c

+1 −0

Original line number	Diff line number	Diff line
		@@ -5917,6 +5917,7 @@ static void svm_cpuid_update(struct kvm_vcpu *vcpu)
		struct vcpu_svm *svm = to_svm(vcpu);

		vcpu->arch.xsaves_enabled = guest_cpuid_has(vcpu, X86_FEATURE_XSAVE) &&
		boot_cpu_has(X86_FEATURE_XSAVE) &&
		boot_cpu_has(X86_FEATURE_XSAVES);

		/* Update nrips enabled cache */

arch/x86/kvm/vmx/vmx.c

+1 −0

Original line number	Diff line number	Diff line
		@@ -4049,6 +4049,7 @@ static void vmx_compute_secondary_exec_control(struct vcpu_vmx *vmx)
		if (vmx_xsaves_supported()) {
		/* Exposing XSAVES only when XSAVE is exposed */
		bool xsaves_enabled =
		boot_cpu_has(X86_FEATURE_XSAVE) &&
		guest_cpuid_has(vcpu, X86_FEATURE_XSAVE) &&
		guest_cpuid_has(vcpu, X86_FEATURE_XSAVES);

Admin message