KVM: SVM: check CR4 changes against vcpu->arch

Similarly to what vmx/vmx.c does, use vcpu->arch.cr4 to check if CR4
bits PGE, PKE and OSXSAVE have changed.  When switching between VMCB01
and VMCB02, CPUID has to be adjusted every time if CR4.PKE or CR4.OSXSAVE
change; without this patch, instead, CR4 would be checked against the
previous value for L2 on vmentry, and against the previous value for
L1 on vmexit, and CPUID would not be updated.
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

arch/x86/kvm/svm/svm.c

@@ -1691,7 +1691,7 @@ static bool svm_is_valid_cr4(struct kvm_vcpu *vcpu, unsigned long cr4)
 void svm_set_cr4(struct kvm_vcpu *vcpu, unsigned long cr4)
 {
 	unsigned long host_cr4_mce = cr4_read_shadow() & X86_CR4_MCE;
-	unsigned long old_cr4 = to_svm(vcpu)->vmcb->save.cr4;
+	unsigned long old_cr4 = vcpu->arch.cr4;
 
 	if (npt_enabled && ((old_cr4 ^ cr4) & X86_CR4_PGE))
 		svm_flush_tlb(vcpu);